tag:blogger.com,1999:blog-75803708659862714172024-02-11T16:11:06.006-08:00Plant BiotechPlant Biotechnology For Better FutureAndri F Martinhttp://www.blogger.com/profile/11669920311565328714noreply@blogger.comBlogger9125tag:blogger.com,1999:blog-7580370865986271417.post-36779407375602639962015-10-28T22:28:00.002-07:002015-10-28T22:30:03.677-07:00Introduction to Plant Secondary MetabolitesINTRODUCTION<br />
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Secondary metabolites (SM) occur in plants in a high
structural diversity. A typical feature of SM is their storage in relatively
high concentrations, sometimes in organs which do not produce them or as
inactive ‘pro drugs’ that are enzymatically activated in case of danger.
Biochemical and physiological features of secondary metabolism are strongly
correlated with the function of SM: SM are not useless waste products (as
assumed earlier) but important tools of plants needed against herbivores,
microbes (bacteria, fungi) and viruses. Some of the SM also function as signal
molecules to attract pollinating arthropods or seed dispersing animals. During
more than 500 million years of evolution, plants have evolved SM with a wide
variety of biochemical and pharmacological properties. Many SM interact with
proteins (receptors, ion channels, enzymes, cytoskeleton, transcription
factors), DNA/RNA and/or biomembranes. Some of the interactions with molecular
targets are highly specific, others have pleiotropic properties. Potential modes
of action are summarized. As a consequence of the pharmacological properties of
SM, several of them are used in medicine to treat disorders and infections. Others
are interesting in biotechnology as rational pesticides. Phytomedicine normally
employs complex mixtures, as they are present in the producing plant, which may
exert additive or even synergistic properties.</div>
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<br />
<h3>
Primary metabolism vs. Secondary Metabolism</h3>
<br />
<div style="text-align: justify;">
Primary metabolism in a plant comprises all metabolic pathways that are
essential to the plant's survival. Primary metabolites are compounds
that are directly involved in the growth and development of a plant
whereas secondary metabolites are compounds produced in other metabolic
pathways that, although important, are not essential to the functioning
of the plant. However, secondary plant metabolites are useful in the
long term, often for defense purposes, and give plants characteristics
such as color. Secondary plant metabolites are also used in signalling
and regulation of primary metabolic pathways. Plant hormones, which are
secondary metabolites, are often used to regulate the metabolic activity
within cells and oversee the overall development of the plant. As
mentioned above in the History tab, secondary plant metabolites help the
plant maintain an intricate balance with the environment, often
adapting to match the environmental needs. Plant metabolites that color
the plant are a good example of this, as the coloring of a plant can
attract pollinators and also defend against attack by animals (https://en.wikipedia.org/wiki/Plant_secondary_metabolism).</div>
<div style="text-align: justify;">
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://1.bp.blogspot.com/-hQeaARmpDmY/VjGuCzjgxaI/AAAAAAAADXo/0gam7LEdbFE/s1600/Plant%2BSecondary%2BMetabolism.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="Plant secondary metabolism" border="0" height="305" src="http://1.bp.blogspot.com/-hQeaARmpDmY/VjGuCzjgxaI/AAAAAAAADXo/0gam7LEdbFE/s400/Plant%2BSecondary%2BMetabolism.png" title="Plant secondary metabolism" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Secondary Metabolism from photosynthesis</td></tr>
</tbody></table>
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://1.bp.blogspot.com/-PSRAEQSUjS4/VjGuDvYV5OI/AAAAAAAADXs/UUl3C6c9GV0/s1600/Plant%2BSecondary%2BMetabolism_C.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="298" src="http://1.bp.blogspot.com/-PSRAEQSUjS4/VjGuDvYV5OI/AAAAAAAADXs/UUl3C6c9GV0/s400/Plant%2BSecondary%2BMetabolism_C.gif" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Secondary metabolism from glucose</td></tr>
</tbody></table>
<div style="text-align: justify;">
<br /></div>
</div>
Andri F Martinhttp://www.blogger.com/profile/11669920311565328714noreply@blogger.com20tag:blogger.com,1999:blog-7580370865986271417.post-34438706247156219872012-03-15T02:20:00.000-07:002012-03-15T02:20:47.365-07:00Ethylene: The Gaseous Hormone<div style="text-align: justify;">DURING THE NINETEENTH CENTURY, when coal gas was used for street illumination, it was observed that trees in the vicinity of streetlamps defoliated more extensively than other trees. Eventually it became apparent that coal gas and air pollutants affect plant growth and development, and <i>ethylene</i> was identified as the active component of coal gas. In 1901, Dimitry Neljubov, a graduate student at the Botanical Institute of St. Petersburg in Russia, observed that dark-grown pea seedlings growing in the laboratory exhibited symptoms that were later termed the triple response: reduced stem elongation, increased lateral growth (swelling), and abnormal, horizontal growth. When the plants were allowed to grow in fresh air, they regained their normal morphology and rate of growth. Neljubov identified <b>ethylene</b>, which was present in the laboratory air from coal gas, as the molecule causing the response. The first indication that <u>ethylene</u> is a natural product of plant tissues was published by H. H. Cousins in 1910. Cousins reported that “emanations” from oranges stored in a chamber caused the premature ripening of bananas when these gases were passed through a chamber containing the fruit. However, given that oranges synthesize relatively little <b>ethylene</b> compared to other fruits, such as apples, it is likely that the oranges used by Cousins were infected with the fungus Penicillium, which produces copious amounts of <i>ethylene</i>. In 1934, R. Gane and others identified <u>ethylene</u> chemically as a natural product of plant metabolism, and because of its dramatic effects on the plant it was classified as a hormone.</div><br />
<div style="text-align: justify;">For 25 years <u>ethylene</u> was not recognized as an important plant hormone, mainly because many physiologists believed that the effects of <i>ethylene</i> were due to auxin, the first plant hormone to be discovered. Auxin was thought to be the main plant hormone, and <b>ethylene</b> was considered to play only an insignificant and indirect physiological role. Work on <i>ethylene</i> was also hampered by the lack of chemical techniques for its quantification. However, after gas chromatography was introduced in <b>ethylene</b> research in 1959, the importance of <u>ethylene</u> was rediscovered and its physiological significance as a plant growth regulator was recognized (Burg and Thimann 1959). In this chapter we will describe the discovery of the <i>ethylene</i> biosynthetic pathway and outline some of the important effects of <u>ethylene</u> on plant growth and development. At the end of the chapter we will consider how <i>ethylene</i> acts at the cellular and molecular levels.</div><br />
<b>STRUCTURE, BIOSYNTHESIS, AND MEASUREMENT OF <i>ETHYLENE</i></b><br />
<br />
<div style="text-align: justify;"><i>Ethylene</i> can be produced by almost all parts of higher plants, although the rate of production depends on the type of tissue and the stage of development. In general, meristematic regions and nodal regions are the most active in <u>ethylene</u> biosynthesis. However, <b>ethylene</b> production also increases during leaf abscission and flower senescence, as well as during fruit ripening. Any type of wounding can induce <b>ethylene</b> biosynthesis, as can physiological stresses such as flooding, chilling, disease, and temperature or drought stress. The amino acid methionine is the precursor of <i>ethylene</i>, and ACC (1-aminocyclopropane-1-carboxylic acid) serves as an intermediate in the conversion of methionine to <u>ethylene</u>. As we will see, the complete pathway is a cycle, taking its place among the many metabolic cycles that operate in plant cells.</div><div style="text-align: justify;"><br />
</div><div style="text-align: justify;"><b>The Properties of <i>Ethylene</i> Are Deceptively Simple</b><br />
</div><div style="text-align: justify;"><u>Ethylene</u> is the simplest known olefin (its molecular weight is 28), and it is lighter than air under physiological conditions:</div><div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-5bl5czjY89c/T2GvPDA3PLI/AAAAAAAACDc/ol0r-llUfbs/s1600/Ethylene.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="181" src="http://3.bp.blogspot.com/-5bl5czjY89c/T2GvPDA3PLI/AAAAAAAACDc/ol0r-llUfbs/s200/Ethylene.jpg" width="200" /></a></div><div style="text-align: justify;"><br />
</div> It is flammable and readily undergoes oxidation. <u>Ethylene</u> can be oxidized to <b>ethylene</b> oxide:<br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://1.bp.blogspot.com/-PGeN_eTm1E8/T2GvP7PZlJI/AAAAAAAACDg/9rFgrMBDviE/s1600/Ethylene+Oxide.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="200" src="http://1.bp.blogspot.com/-PGeN_eTm1E8/T2GvP7PZlJI/AAAAAAAACDg/9rFgrMBDviE/s200/Ethylene+Oxide.jpg" width="195" /></a></div> and <u>ethylene</u> oxide can be hydrolyzed to <i>ethylene</i> glycol:<br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-3DLzYUYiOoo/T2GvQbyN8FI/AAAAAAAACDo/RVd7-PzkTc4/s1600/Ethylene+glycol.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="166" src="http://3.bp.blogspot.com/-3DLzYUYiOoo/T2GvQbyN8FI/AAAAAAAACDo/RVd7-PzkTc4/s200/Ethylene+glycol.jpg" width="200" /></a></div><br />
In most plant tissues, <u>ethylene</u> can be completely oxidized to CO2, in the following reaction:<br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://1.bp.blogspot.com/-PIpIRU3bidU/T2GwJX1kfmI/AAAAAAAACD0/gotTN0_plwg/s1600/Oxydation+of+Ethylene.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="96" src="http://1.bp.blogspot.com/-PIpIRU3bidU/T2GwJX1kfmI/AAAAAAAACD0/gotTN0_plwg/s320/Oxydation+of+Ethylene.jpg" width="320" /></a></div><br />
<b>Ethylene</b> is released easily from the tissue and diffuses in the gas phase through the intercellular spaces and outside the tissue. At an <u>ethylene</u> concentration of 1 uL L–1 in the gas phase at 25°C, the concentration of <u>ethylene</u> in water is 4.4 x 10–9 M. Because they are easier to measure, gas phase concentrations are normally given for <i>ethylene</i>. Because <b>ethylene</b> gas is easily lost from the tissue and may affect other tissues or organs, <i>ethylene</i>-trapping systems are used during the storage of fruits, vegetables, and flowers. Potassium permanganate (KMnO4) is an effective absorbent of <i>ethylene</i> and can reduce the concentration of <u>ethylene</u> in apple storage areas from 250 to 10 uL L–1, markedly extending the storage life of the fruit.<br />
<br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-oeKRr01Oye4/T2GvEdVchbI/AAAAAAAACD4/VM8EvlNhs-A/s1600/Ethylene+Biosynthesis.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="576" src="http://3.bp.blogspot.com/-oeKRr01Oye4/T2GvEdVchbI/AAAAAAAACD4/VM8EvlNhs-A/s640/Ethylene+Biosynthesis.jpg" width="640" /></a></div>Andri F Martinhttp://www.blogger.com/profile/11669920311565328714noreply@blogger.com3tag:blogger.com,1999:blog-7580370865986271417.post-69345153350935890422011-12-13T21:45:00.000-08:002011-12-13T21:45:24.532-08:00Abscisic Acid (ABA)<h1>OCCURRENCE AND ACTIVITY OF ABSCISIC ACID</h1><br />
<div style="text-align: justify;"><span style="font-family: "TimesNewRoman","serif"; font-size: small;"><b>Abscisic acid (ABA)</b> (</span><span lang="EN-US" style="font-family: "TimesNewRoman","serif"; font-size: small;">Figure 1.</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">) is another naturally occurring</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"><a href="http://plantbiotechinfo.blogspot.com/search/label/Plant%20Hormones">Plant Hormone</a>. It is a 15-carbon acid;</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">four stereoisomers exist, differing in the orientation</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">of the carboxyl group and the attachment of the</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">sidechain to the ring. The naturally-occurring form is</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><i><span style="font-size: small;"><span style="font-family: "TimesNewRoman,Italic","serif";">S</span></span></i><span style="font-family: "TimesNewRoman","serif"; font-size: small;"><i>-(+)-ABA</i>. Commercially available <u>abscisic acid</u> is</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">a mixture of isomers. <i>ABA</i> appears to be produced</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">as a cleavage product of certain carotenoids -</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">xanthophylls - yielding xanthoxin, which is converted</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">to<b> ABA</b> aldehyde and hence to <i>ABA</i> (Zeevart,</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">1999). It has long been known that</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">dehydration of plant tissue leads to increased</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">biosynthesis of <b>ABA</b> (Wright and Hiron, 1969);</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">however, it is now well-established that a number of</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">other environmental factors - low (Vernieri </span><span style="font-size: small;"><i><span style="font-family: "TimesNewRoman,Italic","serif";">et al.,</span></i><i><span style="font-family: "TimesNewRoman,Italic","serif";"> </span></i></span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">1991) and high temperatures (Daie and Campbell,</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">1981), salinity (Kefu </span><span style="font-size: small;"><i><span style="font-family: "TimesNewRoman,Italic","serif";">et al., </span></i></span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">1991) and flooding</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">(Jackson, 1991) - can also produce the same effect.</span></div><div class="MsoNormal" style="line-height: normal; margin-bottom: 0cm;"><span style="font-size: small;"><br />
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</span></div><div class="MsoNormal" style="line-height: normal; margin-bottom: 0cm; text-align: center;"><span lang="EN-US" style="font-size: small;">Figure 1. abscisic acid (ABA)</span></div><div class="MsoNormal" style="line-height: normal; margin-bottom: 0.0001pt;"><span style="font-size: small;"><br />
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<h2><span style="font-size: small;">Abscisic Acid (ABA) Metabolism</span></h2><br />
<span style="font-size: small;"> </span></div><div class="MsoNormal" style="line-height: normal; margin-bottom: 0.0001pt; text-align: justify;"><span style="font-family: "TimesNewRoman","serif"; font-size: small;"><b>ABA </b>catabolism is complex involving either</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">oxidation/reduction - to phaseic acid and</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">dihydrophaseic acid - or conjugation to produce the</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">glucose ester or glucoside (Zeevart, 1999).</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">Biosynthesis occurs in plastids (especially</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">chloroplasts) (Milborrow, 1974). The herbicide</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">‘fluridone’ (Figure 2.), which inhibits the natural production</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">of carotenoids (Bartels and Watson, 1978), can</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">prevent <u>ABA </u>biosynthesis (Moore and Smith, 1984).</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">Norflurazon (Figure 3.) produces the same effect.</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"><b>Abscisic acid</b> is found ubiquitously in plants and</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">is the most commonly identified of a number of other</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">structurally related natural compounds, which have</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">plant growth regulatory activity. It has often been</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">regarded as being a plant growth inhibitor, partly</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">because of its early history, which involved studies</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">on bud dormancy and abscission. However, <i>ABA</i> has many roles in plants, such as the regulation of </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">stomatal closure, control of water and ion uptake by</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">roots, and of leaf abscission and senescence and</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">hence, like other hormones has multifaceted effects.</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">In tissue cultures, it sometimes promotes</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">morphogenesis or growth. The quantity present in</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">plant cultures can be determined by gas</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">chromatography mass spectrometry or ELISA,</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">following purification by high-pressure liquid</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">chromatography (Ryu </span><span style="font-size: small;"><i><span style="font-family: "TimesNewRoman,Italic","serif";">et al., </span></i></span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">1988). Uptake of <u>ABA</u></span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">into tissues appears to be by simple diffusion of the</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">undissociated molecule, the anions being trapped</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">upon entry into cells. It is decreased at pH levels</span><span style="font-family: "TimesNewRoman","serif"; font-size: small;"> </span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">above 5.5 (Minocha and Nissen, 1985; Patel </span><span style="font-size: small;"><i><span style="font-family: "TimesNewRoman,Italic","serif";">et al.,</span><span style="font-family: "TimesNewRoman,Italic","serif";"> </span></i></span><span style="font-family: "TimesNewRoman","serif"; font-size: small;">1986).</span></div><div class="MsoNormal" style="line-height: normal; margin-bottom: 0.0001pt;"><span style="font-size: small;"><br />
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</div><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-2-U1Boq0DsA/TuYuPl_2vAI/AAAAAAAABQE/yZC18HS9K60/s1600/Fluridone.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="202" src="http://4.bp.blogspot.com/-2-U1Boq0DsA/TuYuPl_2vAI/AAAAAAAABQE/yZC18HS9K60/s320/Fluridone.jpg" width="320" /> </a></div><div class="separator" style="clear: both; text-align: center;">Figure 2. Fluridon </div><br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-uAhs0lGjctk/TuYuQiu2UoI/AAAAAAAABQI/KkRbT3BDq_0/s1600/nirflurazon.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="188" src="http://3.bp.blogspot.com/-uAhs0lGjctk/TuYuQiu2UoI/AAAAAAAABQI/KkRbT3BDq_0/s320/nirflurazon.jpg" width="320" /> </a></div><div class="separator" style="clear: both; text-align: center;">Figure 3. norflurazon </div><div class="MsoNormal" style="line-height: normal; margin-bottom: 0.0001pt;"><br />
</div><div class="MsoNormal" style="font-family: Verdana,sans-serif; line-height: normal; margin-bottom: 0cm; text-align: justify;"><span style="font-size: 10pt;"><span style="font-family: Times,"Times New Roman",serif; font-size: small;">The early stages of<b> ABA </b>action probably follow</span></span><span style="font-family: Times,"Times New Roman",serif; font-size: small;"> </span><span style="font-family: Times,"Times New Roman",serif; font-size: small;">the same types of mechanism as those for other</span><span style="font-family: Times,"Times New Roman",serif; font-size: small;"> </span><span style="font-family: Times,"Times New Roman",serif; font-size: small;">hormones that is, transduction chains leading to</span><span style="font-family: Times,"Times New Roman",serif; font-size: small;"> </span><span style="font-family: Times,"Times New Roman",serif; font-size: small;">changed transcription and translation patterns, or</span><span style="font-family: Times,"Times New Roman",serif; font-size: small;"> </span><span style="font-family: Times,"Times New Roman",serif; font-size: small;">effects on transmembrane ion pumps (as in the case</span><span style="font-family: Times,"Times New Roman",serif; font-size: small;"> </span><span style="font-family: Times,"Times New Roman",serif; font-size: small;">of stomata) (see Assman and Armstrong, 1999; Busk</span><span style="font-family: Times,"Times New Roman",serif; font-size: small;"> </span><span style="font-family: Times,"Times New Roman",serif; font-size: small;"><i>et al., </i></span><span style="font-family: Times,"Times New Roman",serif; font-size: small;">1999). More specifically, <i>ABA</i> has been</span><span style="font-family: Times,"Times New Roman",serif; font-size: small;"> </span><span style="font-family: Times,"Times New Roman",serif; font-size: small;">shown to control the expression of genes specific to</span><span style="font-family: Times,"Times New Roman",serif; font-size: small;"> </span><span style="font-family: Times,"Times New Roman",serif; font-size: small;">embryo development and maturation. Thus, using</span><span style="font-family: Times,"Times New Roman",serif; font-size: small;"> </span><span style="font-family: Times,"Times New Roman",serif; font-size: small;"><b>ABA</b>-deficient and <u>ABA</u>-insensitive </span><span style="font-family: Times,"Times New Roman",serif; font-size: small;"><i>Arabidopsis</i><i> </i></span><span style="font-family: Times,"Times New Roman",serif; font-size: small;">mutants <u>ABA</u> has been shown to control genes for</span><span style="font-family: Times,"Times New Roman",serif; font-size: small;"> </span><span style="font-family: Times,"Times New Roman",serif; font-size: small;">both LEA (late embryogenesis abundant) and storage</span><span style="font-family: Times,"Times New Roman",serif; font-size: small;"> </span><span style="font-family: Times,"Times New Roman",serif; font-size: small;">proteins (see Dodeman </span><span style="font-family: Times,"Times New Roman",serif; font-size: small;"><i>et al., </i></span><span style="font-family: Times,"Times New Roman",serif; font-size: small;">1997).</span></div><div class="MsoNormal" style="line-height: normal; margin-bottom: 0.0001pt;"><br />
</div><div class="separator" style="clear: both; text-align: center;"><a href="http://1.bp.blogspot.com/-xQjX7OqcaGw/TuYy5uXb0YI/AAAAAAAABQQ/urcshHoJ8fI/s1600/ABA+biosynthesis.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="640" src="http://1.bp.blogspot.com/-xQjX7OqcaGw/TuYy5uXb0YI/AAAAAAAABQQ/urcshHoJ8fI/s640/ABA+biosynthesis.jpg" width="531" /> </a></div><div class="separator" style="clear: both; text-align: center;">Figure 4. ABA biosynthesis </div><div class="MsoNormal" style="line-height: normal; margin-bottom: 0.0001pt;"><br />
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</div><div class="MsoNormal" style="line-height: normal; margin-bottom: 0.0001pt;"></div><div class="MsoNormal" style="line-height: normal; margin-bottom: .0001pt; margin-bottom: 0cm; mso-layout-grid-align: none; text-autospace: none;"><div style="font-family: Times,"Times New Roman",serif; text-align: justify;"><span style="font-size: small;">At another level, some of the effects of <b>ABA</b> lie</span><span style="font-size: small;"> </span><span style="font-size: small;">in the hormone antagonising or modifying the effects</span><span style="font-size: small;"> </span><span style="font-size: small;">of other hormones, notably <a href="http://plantbiotechinfo.blogspot.com/search/label/Cytokinin">cytokinins</a> and</span><span style="font-size: small;"> </span><span style="font-size: small;"><a href="http://plantbiotechinfo.blogspot.com/search/label/Gibberellins">gibberellins</a>, but also <a href="http://plantbiotechinfo.blogspot.com/search/label/Auxin">auxins</a>. For example, Charriere</span><span style="font-size: small;"> <i>et al., </i></span><span style="font-size: small;">(1999) have suggested that the effect of <i>ABA</i></span><span style="font-size: small;"> </span><span style="font-size: small;">on morphogenesis in zygotic embryos of <i>Helianthus</i><i> </i><i>annuus </i></span><span style="font-size: small;">is indirect and due to a modification of auxin</span><span style="font-size: small;"> </span><span style="font-size: small;">levels</span><span style="font-size: small;">.</span></div><br />
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</div>Andri F Martinhttp://www.blogger.com/profile/11669920311565328714noreply@blogger.com0tag:blogger.com,1999:blog-7580370865986271417.post-85935543101120970822011-11-14T21:35:00.000-08:002015-11-04T17:39:09.226-08:00Gibberellins<div style="font-family: inherit;">
<h1 style="text-align: left;">
NATURAL OCCURRENCE AND PHYSIOLOGICAL ACTIVITY OF GIBBERELLINS</h1>
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<span class="maintext">Unlike the classification of auxins which are classified on the basis of function, <b>gibberellins</b> are classified on the basis of structure as well as function.</span> More than 100 members of this group of <a href="http://plantbiotechinfo.blogspot.com/search/label/Plant%20Hormones">plant hormones</a> are now known. They all share gibbane ring structures and are either dicarboxylic (CB20B) or monocarboxylic (CB19B), they have all been assigned ‘<i>gibberellin</i> numbers’ (GABxB) and are usually referred to by these rather than by conventional chemical nomenclature. No plant appears to possess all of the <u>gibberellins</u>, some have only been found in fungi and some only in higher plants; nor are the various gibberellins equally active, some are precursors and some catabolites of active <b>gibberellins</b>. GAB1B (1) is the most active <u>gibberellin </u>in the promotion of cell elongation. Very few gibberellins are available commercially and GAB3B (2) or a mixture of GAB4 B(3) and GAB7B (4) have been used most frequently in <a href="http://plantbiotechinfo.blogspot.com/2011/07/plant-tissue-culture-introduction.html">plant culture</a>.</div>
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<u>Gibberellins</u> are involved in a wide range of developmental responses. These include promotion of elongation in stems and grass leaves, due in part to activation of the intercalary meristem. Another important role of <i>gibberellins </i>is the induction of hydrolytic enzymes such as α-amylase and protease in the seeds of grasses and cereals, hence facilitating endosperm mobilisation. Other roles in some plants include the promotion of seed germination, bolting of rosette plants, sex determination, fruit development and the control of juvenility.<br />
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<h2>
BIOSYNTHESIS OF GIBBERELLINS</h2>
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The biosynthetic pathway(s) for <u>gibberellins </u>are very complex. All start from isopentenyl diphosphate which in response to soluble cyclases produces ent-kaurene(in plastids). Membrane monoxygenases then convert this to the common precursor GAB12B aldehyde which - in a series of steps involving hydroxylases and oxidases - yields the active <b>gibberellins </b>(see Hedden, 1999). Very little is known about the early steps in <i>gibberellin</i> signal transduction. It is clear however that later steps involve selective gene transcription and de novo protein synthesis.<br />
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<h3>
Inhibitors of biosynthesis and action</h3>
Because very little is known about the mode of action of <u>gibberellins </u>it is doubtful that the action of any of the substances known to affect developmental responses involving these growth regulators is due to effects early in signal transduction. On the other hand, much is known about a wide range of synthetic substances, often called 'antigibberellins', which act by blocking biosynthetic pathways.</div>
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hese were in general developed to achieve desirable agricultural outcomes - for example dwarfing of cereals to prevent lodging.These substances fall into four categories (see Rademacher, 2000). A number of quaternary ammonium, phosphonium and sulphonium salts act by inhibiting the cyclisation process. Examples of this type are chlormequat chloride (CCC) (5) and AMO 1618 (6). Certain heterocyclic nitrogen-containing compounds such as ancymidol (7), paclobutrazol (8), uniconazole-P (9) and tetcyclasis (10) appear to act by inhibiting ent-kaurene oxidase. A further group of inhibitors are the acylcyclohexanedione derivatives, for example prohexadione (11) and daminozide (12), which affect the later steps of <b>gibberellin </b>biosynthesis involving hydroxylases. While the inhibitors may be useful tools, it should be noted that none are absolutely specific and may affect other biosynthetic pathways such as those for sterols and abscisic acid. Lastly, the inhibitor, 16,17-dihydro GAB5B (13) and related structures appear to act by mimicking the natural substrates.<br />
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<span class="maintext" style="font-family: "arial";"> </span><span style="font-family: "arial";"><span class="maintext"> </span></span>Andri F Martinhttp://www.blogger.com/profile/11669920311565328714noreply@blogger.com1tag:blogger.com,1999:blog-7580370865986271417.post-83242577907143871512011-10-27T17:36:00.000-07:002011-10-27T17:52:28.341-07:00Cytokinins<h1 style="text-align: justify;">Cytokinins</h1><div style="text-align: justify;"></div><div style="text-align: justify;"><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://4.bp.blogspot.com/-nptKlaVVoRA/Tqn3_ab7lBI/AAAAAAAABAs/BCNyBhVCktw/s1600/Zeatin.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" src="http://4.bp.blogspot.com/-nptKlaVVoRA/Tqn3_ab7lBI/AAAAAAAABAs/BCNyBhVCktw/s1600/Zeatin.png" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Zeatin</td></tr>
</tbody></table><b> Cytokinins</b> are complex class of <a href="http://plantbiotechinfo.blogspot.com/search/label/Plant%20Hormones">plant hormones</a>. The naturally occurring cytokinins include Zeatin (Z), iP (Isopentenyl adenine), and (Dihydrozeatin)DHZ and their ribosides zeatinriboside (ZR), iPA (Isopentenyl adenine riboside) and DHZR. In addition, conjugated (non-active) and phosphorylated (active) <i>cytokinins </i>have been isolated from plant tissues. For a long time, BAP has been considered to be a synthetic <u>cytokinin</u>, but has been recently shown a naturally occurring one. In addition to these cytokinins that are all of the purine-type, <i>nonpurine cytokinins</i> have been reported such as thidiazuron (TDZ) and CPPU (4-PU-30). These compounds have a very high<b> cytokinin</b> activity and are particularly successful in woody plants. TDZ is used commercially as a cotton defoliant. In this case, it acts by inducing ethylene synthesis. Meta-topolin is a highly active aromatic <a href="http://plantphys.info/plant_physiology/cytokinin.shtml"><u>cytokinin</u></a> that was first isolated from <i>Populus</i>. In tissue culture, BAP and the synthetic <b>cytokinins</b> kinetin and TDZ are most frequently used.<br />
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Natural <i>cytokinins</i> :<br />
<ol><li>Zeatin</li>
<li>Dihydrozeatin</li>
<li>Isopentenyl adenine</li>
<li>Isopentenyl adenine riboside </li>
<li>Dihydrozeatin riboside</li>
<li>Zeatin riboside</li>
</ol>Synthetic <i>cytokinins</i> :<br />
<ol><li>Kinetin</li>
<li>Benzyl Amino Purine (BAP)</li>
<li>Tetrahydropyranyl Benzyladenine</li>
</ol></div><div style="text-align: justify;"><h2>Effects of Cytokinins</h2></div><div style="text-align: justify;">The discovery of <u>cytokinins</u> is closely linked to <i>tissue culture</i>. In the starting period of <a href="http://plantbiotechinfo.blogspot.com/2011/07/plant-tissue-culture-introduction.html">plant tissue culture</a>, it was observed that malt, coconut and yeast extracts promote both the growth and initiation of buds in vitro. Because these preparations all contain purines, nucleic acids were tested. It was observed that autoclaving of nucleic acids strongly enhanced their effect. The active compound formed by autoclaving appeared to be kinetin, a hitherto unknown purine. In 1964, Letham isolated zeatin from immature corn.</div><div style="text-align: justify;"><div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-Zy4lJmUnaYU/Tqn3QlguE0I/AAAAAAAABAE/5rVusZ94lA4/s1600/Cytokinin+callus+response.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="http://2.bp.blogspot.com/-Zy4lJmUnaYU/Tqn3QlguE0I/AAAAAAAABAE/5rVusZ94lA4/s320/Cytokinin+callus+response.gif" width="320" /></a></div><br />
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</div><div style="text-align: justify;"><b>Cytokinins</b> promote cell division, but they likely influence another step in the cell cycle than <a href="http://plantbiotechinfo.blogspot.com/search/label/Auxin">auxins</a>. Thus, addition of <b>cytokinins</b> is usually required to obtain callus growth. In micropropagation, <i>cytokinins</i> are applied to promote axillary branching. High concentrations of <u>cytokinin</u> lead to extreme bushiness. This may result in undesirable bushiness long after transfer of micropropagated plantlets to soil. Transformation of plants with the <u>cytokinin</u> biosynthetic gene of <i>A. tumefaciens</i> may result in plants with reduced apical dominance. Other applications of <i>cytokinin</i> in tissue culture are promotion of adventitious shoot formation, prevention of senescence, reversion of the deteriorating effect of auxin on shoots, and occasionally, inhibition of excessive root formation (e.g., in germinating somatic embryos.). <u>Cytokinins</u> inhibit root formation and are therefore omitted from rooting media. <b>Cytokinins</b> may have other undesirable side-effects such as hyperhydricity and loss of the chimeric structure.</div><div style="text-align: justify;"><br />
</div><div style="text-align: justify;"><h3>Transport, uptake and metabolism of Cytokinins.</h3></div><div style="text-align: justify;"><div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-YZCnVE0CHxE/Tqn3RwDkODI/AAAAAAAABAM/W9xBp6OGEn8/s1600/cytokinin+synthesis.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="http://3.bp.blogspot.com/-YZCnVE0CHxE/Tqn3RwDkODI/AAAAAAAABAM/W9xBp6OGEn8/s320/cytokinin+synthesis.gif" width="320" /></a></div><br />
Roots are considered as the main site of <b>cytokinin</b> synthesis and <i>cytokinins</i> is transported to the shoot via the water flow in the xylem. Xylem exudates contain high levels of <u>cytokinins</u>. Recently, evidence has been found for active transport via carriers.</div><div style="text-align: justify;">When plant tissues are cultured on medium with cytokinins, they are rapidly taken up, although at a much smaller rate than auxin (3 to 10 times slower). It is not known how <i>cytokinins</i> reach target tissues like axillary buds (to break apical dominance) and leaves (to reduce senescence) which both are relatively large distance from the source but probably <b>cytokinins</b> are transported via water flow in the vascular tissues. Zeatin, ZR, iP and iPA are conjugated and/or oxidized by plant tissues. Oxidation involves oxidative side chain cleavage. DHZ, DHZR and BAP are conjugated but not oxidized. <i>Cytokinins</i> can be N-glucosylated on the purine ring or O-glucosylated on the N6-substituted side-chain. The N-glucosides are biologically inactive and stable. The O-glucosides, that are formed from Zeatin and DHZ may have a storage function. Just as with other plant hormones, aftger uptake only a very small percentage of <u>cytokinin</u> remains in the free form. TDZ is an exception and is conjugated only at very low rate: after long periods (12 to 33 days) of culture of <i>Phaseolus </i>callus on medium with radioactive labeled TDZ, 60% of the TDZ taken up from the mdium was in the free, non-conjugated form. BAP is chemically stable <i>cytokinin</i> in tissue culture medium, whereas most other purine-type <b>cytokinins</b> are considered to be to some extent chemically unstable. The nonpurine type <u>cytokinins</u> CPPU and TDZ are chemically stable.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-20AKmgt51vI/Tqn3RR9EqjI/AAAAAAAABAI/9QCppky-uDM/s1600/cytokinin+conjugated.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="http://2.bp.blogspot.com/-20AKmgt51vI/Tqn3RR9EqjI/AAAAAAAABAI/9QCppky-uDM/s320/cytokinin+conjugated.gif" width="320" /></a></div></div><div style="text-align: justify;">Compounds that influence <i>cytokinin</i> oxidation (phenolic compounds), conjugation and action, have been studed occasionally. They have hardly been used in tissue culture. The synthesis of <b>cytokinins</b> is inhibited by <a href="http://en.wikipedia.org/wiki/Lovastatin">lovastatin</a> or <a href="http://en.wikipedia.org/wiki/Simvastatin">simvastatin</a> In human medicine statins are used to lower cholesterol.<br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-EOS8rg1Uq1A/Tqn3SOmcybI/AAAAAAAABAQ/RLMYMJ4lCS4/s1600/iaa+kinetin+interaction.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-EOS8rg1Uq1A/Tqn3SOmcybI/AAAAAAAABAQ/RLMYMJ4lCS4/s1600/iaa+kinetin+interaction.gif" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="http://1.bp.blogspot.com/-1W9tM2QfBYw/Tqn3UDS3XlI/AAAAAAAABAk/1lYvB5bj6nI/s1600/tissuehormones.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="http://1.bp.blogspot.com/-1W9tM2QfBYw/Tqn3UDS3XlI/AAAAAAAABAk/1lYvB5bj6nI/s320/tissuehormones.gif" width="320" /></a></div></div><div style="text-align: justify;"><br />
<a href="http://plantphys.info/plant_physiology/cytokinin.shtml">Picture source</a></div>Andri F Martinhttp://www.blogger.com/profile/11669920311565328714noreply@blogger.com1tag:blogger.com,1999:blog-7580370865986271417.post-6573185029003708752011-10-11T12:24:00.000-07:002011-10-15T16:53:10.696-07:00Auxins<h2 style="font-family: inherit;"><b>Nature of Auxins</b></h2><div style="font-family: inherit;"></div><div style="font-family: inherit; text-align: justify;"><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-H_tJLIPl2hM/TpSKKm2vV_I/AAAAAAAAA10/5lbrn5B9ypY/s1600/Auxin+%252823%2529.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="153" src="http://4.bp.blogspot.com/-H_tJLIPl2hM/TpSKKm2vV_I/AAAAAAAAA10/5lbrn5B9ypY/s200/Auxin+%252823%2529.jpg" width="200" /></a></div>The term <b>auxin</b> is from the Greek articulate auxein which means to grow. Compounds are broadly considered <u>auxins</u> if they can be characterized by their ability to induct cell elongation in stems and otherwise resemble indoleacetic acid (the first <u>auxin</u> isolated) in physiological activity. <i>Auxins</i> usually affect another action in addition to cell elongation of stem cells but this feature is considered critical of all <b>auxins</b> and thus "helps" define the hormone (Arteca, 1996; Mauseth, 1991; Raven, 1992; Salisbury and Ross, 1992).</div><h2 style="font-family: inherit;"><b> Discovery of Auxins</b></h2><div style="font-family: inherit;"></div><div style="font-family: inherit; text-align: justify;"><b>Auxins</b> were the first plant hormones determined. Charles Darwin was among the first scientists to dabble in <a href="http://plantbiotechinfo.blogspot.com/2011/10/plant-hormones-and-growth-regulators.html">plant hormone</a> research. In his book "The Power of Movement in Plants" presented in 1880, he first describes the outcomes of light on motion of canary grass (<i>Phalaris canariensis</i>) coleoptiles.</div><div style="font-family: inherit;"><br />
</div><div style="font-family: inherit; text-align: justify;">Darwin's try out advised that the tip of the coleoptile was the tissue contributing for perceiving the light and raising some signal which was transported to the lower part of the coleoptile where the physiological response of bending occurred. He then cut off the tip of the coleoptile and exposed the rest of the coleoptile to unidirectional light to see if curving occurred. Curvature did not occur encouraging the results of his first experiment (Darwin, 1880).</div><div style="font-family: inherit;"><br />
</div><div class="separator" style="clear: both; font-family: inherit; text-align: center;"><a href="http://4.bp.blogspot.com/-VKpzFpyryfc/TpSKfByUByI/AAAAAAAAA30/ZpQaWWF5YR8/s1600/darwintip.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="http://4.bp.blogspot.com/-VKpzFpyryfc/TpSKfByUByI/AAAAAAAAA30/ZpQaWWF5YR8/s320/darwintip.gif" width="320" /></a></div><div style="font-family: inherit;"></div><div style="font-family: inherit;"><br />
</div><div style="font-family: inherit; text-align: justify;">In 1913, Boysen-Jensen altered Fritting's experimentation by inserting parts of mica to block the transfer of the signal and showed that transport of <i>auxin</i> toward the base occurs on the dark side of the plant as contradicted to the side open to the unidirectional light (Boysen-Jensen, 1913). In 1918, Paal supported Boysen-Jensen's results by cutting off coleoptile tips in the dark, uncovering only the tips to the light, replacing the coleoptile tips on the plant but off centered to one side or the other. Results showed that whichever side was exposed to the coleoptile, curvature occurred toward the other side (Paal, 1918). Soding was the next scientist to extend <b>auxin</b> research by extending on Paal's idea. He showed that if tips were cut off there was a reduction in growth but if they were cut off and then replaced growth continued to occur (Soding, 1925).</div><div style="font-family: inherit;"><br />
</div><div style="font-family: inherit; text-align: justify;">In 1926, a graduate student from Holland by the name of Fritz Went publicized a paper describing how he isolated a plant growth substance by placing agar blocks under coleoptile tips for a period of time then removing them and placing them on decapitated Avena stems (Went, 1926). After placement of the agar, the stems resumed growth (see below). In 1928, Went developed a method of quantifying this plant growth substance. His results suggested that the curvatures of stems were proportional to the amount of growth substance in the agar (Went, 1928). This test was called the avena curvature test.(see below)</div><div class="separator" style="clear: both; font-family: inherit; text-align: center;"><a href="http://3.bp.blogspot.com/-KiHNXtqwVkY/TpSK83qWfHI/AAAAAAAAA74/IUfWtmYPjCs/s1600/paaltip.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="http://3.bp.blogspot.com/-KiHNXtqwVkY/TpSK83qWfHI/AAAAAAAAA74/IUfWtmYPjCs/s320/paaltip.gif" width="320" /></a></div><div style="font-family: inherit;"><br />
</div><div style="font-family: inherit; text-align: justify;">Went called the hormone <b>auxin</b> (auxein: to grow). It took 20 years before this <i>auxin</i> was identified chemically as<i> indole-3-acetic acid</i>. Since then additional natural <u>auxins</u> have been identified. </div><div style="font-family: inherit;"><br />
</div><div style="font-family: inherit; text-align: justify;">Much of our current knowledge of <b>auxin</b> was obtained from its applications. Went's work had a great influence in stimulating plant growth substance research. He is often credited with dubbing the term <i>auxin</i> but it was actually Kogl and Haagen-Smit who purified the compound auxentriolic acid (<u>auxin</u> A) from human urine in 1931 (Kogl and Haagen-Smit, 1931). Later Kogl isolated other compounds from urine which were similar in structure and function to <b>auxin</b> A, one of which was<i> indole-3 acetic acid</i> (IAA) initially discovered by Salkowski in 1985. In 1954 a committee of plant physiologists was set up to characterize the group <i>auxins</i>. The term comes from the Greek auxein meaning "to grow." Compounds are generally considered <u>auxins</u> if they are synthesized by the plant and are substances which share similar activity to IAA (the first <b>auxin</b> to be isolated from plants) (Arteca, 1996; Davies, 1995). </div><div style="font-family: inherit;"><br />
</div><div style="font-family: inherit;"><u>Auxin</u>, as plant hormone can be divided into two categories : <b>Natural auxins</b> and <b>Synthetic auxins</b></div><div style="font-family: inherit; text-align: left;"><h3>Natural Auxins :</h3></div><ol style="font-family: inherit;"><li><i>indole-3-acetic acid</i> (IAA)</li>
<li><i>4-chloroindole-3-acetic acid</i> (4-Cl-IAA)</li>
<li><i>phenylacetic acid </i>(PAA)</li>
<li><i>indole-3-butyric acid</i> (IBA</li>
</ol><div style="font-family: inherit;"></div><div class="separator" style="clear: both; font-family: inherit; text-align: center;"><a href="http://2.bp.blogspot.com/-d19upxwJDBg/TpSK7a971VI/AAAAAAAAA7w/4QYA5U4CCEY/s1600/naturalauxins.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="http://2.bp.blogspot.com/-d19upxwJDBg/TpSK7a971VI/AAAAAAAAA7w/4QYA5U4CCEY/s320/naturalauxins.gif" width="320" /></a></div><h3 style="font-family: inherit;">Synthetic Auxins :</h3><ol style="font-family: inherit;"><li><i>2,4-Dichlorophenoxyacetic acid</i> (2,4-D)</li>
<li><i>α-Naphthalene acetic acid</i> (α-NAA)</li>
<li><i>2-Methoxy-3,6-dichlorobenzoic acid</i> (dicamba)</li>
<li><i>4-Amino-3,5,6-trichloropicolinic acid</i> (tordon or picloram)</li>
<li><i>2,4,5-Trichlorophenoxyacetic acid</i> (2,4,5-T)</li>
</ol><div style="font-family: inherit;"></div><div class="separator" style="clear: both; font-family: inherit; text-align: center;"><a href="http://1.bp.blogspot.com/-IxS64EG1_w4/TpSLWLot8XI/AAAAAAAAA8w/5RgximcCFh8/s1600/syntheticauxins.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="http://1.bp.blogspot.com/-IxS64EG1_w4/TpSLWLot8XI/AAAAAAAAA8w/5RgximcCFh8/s320/syntheticauxins.gif" width="320" /></a></div><div class="MsoNormal" style="font-family: inherit; margin-bottom: 0cm; text-align: justify;"><b><span lang="EN-US"></span></b><br />
<h2><b><span lang="EN-US"> Effects of auxin</span></b></h2></div><div class="MsoNormal" style="font-family: inherit; margin-bottom: 0cm; text-align: justify;"><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-ls5hdkXZs7U/TpSK3MJ3L7I/AAAAAAAAA7Q/mNDqreoJ_KI/s1600/image063.gif" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="92" src="http://4.bp.blogspot.com/-ls5hdkXZs7U/TpSK3MJ3L7I/AAAAAAAAA7Q/mNDqreoJ_KI/s200/image063.gif" width="200" /></a></div> <span lang="EN-US">The major roles of <b>auxin</b> in tissue culture were established by Skoog and Miller in 1957. They observed that pith tissues excised from tobacco stems form shoots at high cytokinin and low <i>auxin</i> concentration, roots at low cytokinin and high <u>auxin</u> concentration, or callus at intermediate concentrations of both plant hormones. The formation or foots from pith fragments corresponds with the effect of <b>auxin</b> on rooting of cuttings, and the reduction of shoot formation with the inhibition of the outgrowth of axillary buds by <i>auxin</i>. A few years after the classical Skoog and Miller experiment, the formation of somatic embryos was observed after treatment with 2,4-D.</span></div><div class="MsoNormal" style="font-family: inherit; margin-bottom: 0cm; text-align: justify;"><br />
</div><div class="MsoNormal" style="font-family: inherit; margin-bottom: 0cm; text-align: justify;"><div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-3HfQw4HDUQo/TpSKnELs1fI/AAAAAAAAA5A/XG46OknOtXs/s1600/image018.gif" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="133" src="http://2.bp.blogspot.com/-3HfQw4HDUQo/TpSKnELs1fI/AAAAAAAAA5A/XG46OknOtXs/s200/image018.gif" width="200" /></a></div><span lang="EN-US">It should be noted that <i>auxins</i> are only required during the initial phases of adventitious root formation and somatic embryogenesis. After that, they become inhibitory and block the outgrowth of the root initials and embryos. </span></div><div class="MsoNormal" style="font-family: inherit; margin-bottom: 0cm; text-align: justify;"><br />
</div><div class="MsoNormal" style="font-family: inherit; margin-bottom: 0cm; text-align: justify;"><span lang="EN-US">The effect of hormones is restricted bottom a specific period of time during the development and to specific tissues/cells. The rhizogenic action of <b>auxins</b> in apple microcuttings is 24h-96h after start of the rooting treatment and is restricted to specific cells near the interfascicular cambium adjacent to the vascular bundles.</span></div><div class="MsoNormal" style="font-family: inherit; margin-bottom: 0cm; text-align: justify;"><br />
</div><div class="MsoNormal" style="font-family: inherit; margin-bottom: 0cm; text-align: justify;"><div class="separator" style="clear: both; text-align: center;"><a href="http://1.bp.blogspot.com/-ztsmp72YQHk/TpSKROXe2yI/AAAAAAAAA2A/7_L5GZfn-5k/s1600/Auxin+%252826%2529.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="206" src="http://1.bp.blogspot.com/-ztsmp72YQHk/TpSKROXe2yI/AAAAAAAAA2A/7_L5GZfn-5k/s320/Auxin+%252826%2529.jpg" width="320" /></a></div><span lang="EN-US">2,4-D is often referred to as a strong <b>auxin</b> but this only applies to the formation of callus and somatic embryos : 2,4-D is a weak <i>auxin</i> with respect to the formation of adventitious root primordial or the inhibition of axillary buds. In contrast, IAA or IBA are not very effective in the formation of callus and somatic embryos, but show a high performance with the respect to adventitious root formation and inhibition of axillary buds.</span><br />
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<h3><b><span lang="EN-US">Transport, uptake and Metabolism of Auxin</span></b></h3></div><div class="MsoNormal" style="font-family: inherit; margin-bottom: 0.0001pt; text-align: justify;"></div><div class="MsoNormal" style="font-family: inherit; margin-bottom: 0cm; text-align: justify;"><div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-UtaxAwFrlhM/TpSKiFWNzOI/AAAAAAAAA4o/K6uxlQaOEKM/s1600/image008.gif" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="320" src="http://3.bp.blogspot.com/-UtaxAwFrlhM/TpSKiFWNzOI/AAAAAAAAA4o/K6uxlQaOEKM/s320/image008.gif" width="272" /></a></div><span lang="EN-US">In plants, <u>auxin</u> is synthesized predominantly in the apical region and transported downwards. The underlying mechanism of this transport has been examined extensively. Uptake of <b>auxin</b> into cells occurs by diffusion and by active uptake via an influx carrier termed AUX1. The rate of uptake via diffusion depends on the dissociation of the molecule. <i>Auxin</i> in more protonated outside the plasmalemma than inside the cell (in the cell wall the pH is ca. 5.5 but the cytoplasm has a pH of ca. 7; IAA is a weak acid with a pKa of 4.7). The undissociated lipophilic <u>auxin</u> diffuses through the plasmalemma into the cell. In the cytoplasm the anionic form prevails, so <b>auxin</b> cannot easily diffuse out through the plasmalemma and is ‘trapped’ within the cells. <i>Auxin</i> is actively transported out of the cells bey efflux carriers, the PIN-proteins. Because the efflux carriers are located predominantly at the basal side of the cell, <u>auxin</u> is transported from the cell to cell in a basipetal direction, i.e., from apical to basal regions. Inside the cells, <b>auxin</b> moves from the apical to the basal side by diffusion. The rate of <i>auxin</i> transport is ca. one cm.h<sup>-1</sup>. The active <u>auxin</u> transport occurs mainly in xylem parenchyma. Polarity itself is likely a major morphogenetic factor. In addition to directional transport, <b>auxin</b> can also move via water flow in the phloem.</span></div><div class="MsoNormal" style="font-family: inherit; margin-bottom: 0cm; text-align: justify;"><br />
</div><div class="MsoNormal" style="font-family: inherit; margin-bottom: 0cm; text-align: justify;"><span lang="EN-US">When explants are cultured on medium with <b>auxin</b>, it is rapidly taken up probably via the same mechanism as described above (anion-trapping). This result in depletion of the medium. When plant tissues are cultured in liquid medium, most of the <u>auxin</u> may have disappeared from the mdium withi a few days. In solid medium only local exhaustion occurs because the slowness of diffusion over large distances. From the crucial medium components, <i>auxin</i> seems to be the only one that is so very rapidly depleted. The epidermis of plants is relatively impermeable to <i>auxin</i> and most uptake by explants occurs via the cut surface. How <b>auxin</b> reaches target tissues in the explants has not been studied. Roots are formed from founder cells close to the cut ends so <u>auxin</u> may reach these cells by diffusion.</span></div><div class="MsoNormal" style="font-family: inherit; margin-bottom: 0.0001pt; text-align: justify;"><br />
</div><div class="MsoNormal" style="font-family: inherit; margin-bottom: 0.0001pt; text-align: justify;"></div><div class="MsoNormal" style="font-family: inherit; margin-bottom: 0.0001pt; text-align: justify;"><div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-rp_ADVxK_-I/TpSKadybngI/AAAAAAAAA3E/K6Tun9eNNoA/s1600/auxinsynthesis.gif" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="240" src="http://2.bp.blogspot.com/-rp_ADVxK_-I/TpSKadybngI/AAAAAAAAA3E/K6Tun9eNNoA/s320/auxinsynthesis.gif" width="320" /></a></div>Plant tissues inactive <u>auxins</u> by conjugation or enzymatic oxidation. All <i>auxins</i> can be conjugated. It is believed that conjugated <b>auxin</b> is inactive. However, conjugation is reversible and the free, active form may be released. It has been suggested that in the plants an equilibrium exists between the free and conjugated forms. Experimental data show that 2,4-D is slower conjugated than IAA, IBA or NAA. IAA is rapidly oxidized. MS-salts accelerate the rate of IAA oxidation. When using IAA, rapid photooxidation of IAA should be kept in mind. IAA is also unstable during autoclaving, but bioassays and chemical determinations show a loss less than 20%. IBA is slower photooxidized than IAA, whereas other <u>auxins</u> e.g. NAA, are not or only very little photooxidized. Riboflavin may be added to medium to enhance photooxidation of IBA. The photooxidation of IAA and of IBA in the presence of riboflavin may be turned to advantage. For example, in adventitious root formation cultures with IAA may be left in the dark unitl the root meristemoids have been formed by the rhizogenic action of auction (see figure). After that, when <b>auxins</b> have become inhibitory, the cultures are transferred to the light to degrade the <u>auxin</u>. It should be noted for the choice of <i>auxin</i>, chemical stability is only one of the factors to consider. The efficiency with respect to the developmental precess that should be promoted, is another major factor. The endogenous level of <u>auxin</u> and <b>auxin</b> action can be manipulated in various ways. In plant tissues, <b>auxin</b> is actively transported in a polar way. TIBA (triiodobenzoiz acid) and NPA (N-1-naphthylphthalamic acid) block this transport, because these compounds bind to the efflux carrier. The endogenous level of <u>auxin</u> can be increased by transforming plants with the <i>auxin</i> biosynthetic genes of <i style="mso-bidi-font-style: normal;">Agrobacterium tumefaciens</i>. The transformed plants show expected changes in their phenotype. Phenolic compounds (e.g., ferulic acid or phloroglucinol) may inhibit oxidation of applied <i>auxin</i>. This is not specific inhibition of enzymatic oxidation, photooxidation is also inhibited by adding phenolic compounds to the medium. PCIB is a genuine anti-<b>auxin</b> and competes with <i>auxin</i> for the <u>auxin</u> binding site at the <b>auxin</b> receptor.<br />
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<div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-9Imi4h2zeSc/TpSKsR4K37I/AAAAAAAAA54/a8vwMoAbt6U/s1600/image035.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="232" src="http://2.bp.blogspot.com/-9Imi4h2zeSc/TpSKsR4K37I/AAAAAAAAA54/a8vwMoAbt6U/s320/image035.gif" width="320" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-Pp8hntzMZbs/TpSKElBWOqI/AAAAAAAAA1c/RjPEkENG_xg/s1600/Auxin+%252817%2529.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><br />
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</div><div style="font-family: inherit;"><a href="http://www.blogger.com/goog_1068696836"> </a></div><div style="font-family: inherit;"><a href="http://plantcellbiology.masters.grkraj.org/html/Plant_Growth_And_Development3-Plant_Hormones-Auxins.htm">Source of reading 1</a></div><div style="font-family: inherit;"><a href="http://en.wikipedia.org/wiki/Auxin">Source of reading 2</a></div><div style="font-family: inherit;"><a href="http://www.plant-hormones.info/auxins.htm">Source of reading 3</a></div><div style="font-family: inherit;"><a href="http://plantphys.info/plant_physiology/auxin.shtml">Source of reading 4</a></div><div style="font-family: inherit;"><br />
</div><div style="font-family: inherit;"> .</div>Andri F Martinhttp://www.blogger.com/profile/11669920311565328714noreply@blogger.com1tag:blogger.com,1999:blog-7580370865986271417.post-71868994214025909742011-10-06T10:09:00.000-07:002011-12-13T22:12:31.964-08:00Plant Hormones and Growth Regulators<h1 style="text-align: justify;">Plant Growth Regulators and Enzymes</h1><div style="text-align: justify;"></div><div style="text-align: justify;"><div class="separator" style="clear: both; text-align: center;"><a href="http://1.bp.blogspot.com/-Z7ckDLDHvKg/TpCL5nPs9PI/AAAAAAAAAvU/Z3M-g87Ti7w/s1600/Plant+Hormone+hypothetical+distribution.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="320" src="http://1.bp.blogspot.com/-Z7ckDLDHvKg/TpCL5nPs9PI/AAAAAAAAAvU/Z3M-g87Ti7w/s320/Plant+Hormone+hypothetical+distribution.jpg" width="250" /></a></div>Genetic data leads the synthesis and development of <b>enzymes</b> which are vital in all metabolic process within the plant. Almost <i>enzymes</i> are proteins in some form or some other, are created in very little amounts and are developed on locate implying they are not transferred from one portion of the organism to other. Genetic data also regulates the production of <i>hormones</i>, which will be handled shortly. The major difference is that <b>hormones</b> are carried from one section of the plant to another as needed. Vitamins essential in the energizing of <u>enzymes</u> and are made in the cytoplasm and membranes of plant cells. Animals and mankind utilize plants in order to supply some vitamin resources. In general, <u>hormone</u> and vitamin effects are alike and are hard to distinguish in plants, and both are related to in general as <i><b>plant growth regulators</b></i>.</div><div style="text-align: justify;"><br />
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</div><h1 style="text-align: justify;">Plant Hormones</h1><div style="text-align: justify;"></div><div style="text-align: justify;"><div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-lWf2dMLxMYk/TpCMdwgW7tI/AAAAAAAAAvc/O5TzVvdyLgk/s1600/Plant+Hormones+Mechanism.gif" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="256" src="http://3.bp.blogspot.com/-lWf2dMLxMYk/TpCMdwgW7tI/AAAAAAAAAvc/O5TzVvdyLgk/s320/Plant+Hormones+Mechanism.gif" width="320" /></a></div>The <u>hormone</u> concept as developed for animals cannot easily be reassigned to <i>plants</i>. On one hand let plants no as effective shipping system as the blood circulation, on the other hand could no hormone that covers all mentioned standards be isolated, and thirdly have plants no equivalent to the central nervous system of animals for the integration and coordination of all physiological activities.</div><div style="text-align: justify;"><br />
</div><div style="text-align: justify;">Still,<u> plants have regulated growth</u>, plainly established steps of differentiation, different metabolic rates in cells, and – at least partially – a communication between cells, too. The cellular exchange of material is determined by perforations of the cell walls at regular time intervals.</div><div style="text-align: justify;"><br />
</div><div style="text-align: justify;">The search for suitable regulator molecules or effectors was successful. They are known to belong to at least seven unique molecular divisions<br />
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<ol><li> <a href="http://plantbiotechinfo.blogspot.com/2011/10/auxins.html">auxins</a></li>
<li><a href="http://plantbiotechinfo.blogspot.com/2011/10/cytokinins.html">cytokinins</a> </li>
<li><a href="http://plantbiotechinfo.blogspot.com/2011/11/gibberellins.html">gibberellins </a></li>
<li><a href="http://plantbiotechinfo.blogspot.com/2011/12/abscisic-acid-aba.html">abscisic acid</a> </li>
<li>ethylene</li>
<li>jasmonat</li>
<li>Brassinosteroids </li>
</ol></div><ul></ul><div style="text-align: justify;"></div><div style="text-align: justify;"><div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-KbgHimcUQ-g/TpCL4-kNUKI/AAAAAAAAAvQ/t31CPN6OJIY/s1600/Plant_Hormone_Summary.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="231" src="http://3.bp.blogspot.com/-KbgHimcUQ-g/TpCL4-kNUKI/AAAAAAAAAvQ/t31CPN6OJIY/s400/Plant_Hormone_Summary.jpg" width="400" /></a></div><br />
The 2 most important <b>growth hormones of plants</b>, so far believed antagonists, also work synergistically. The activities of <b>auxin </b>and <b>cytokinin</b>, primary molecules for plant growth and the establishment of organs, such as leaves and buds, are in fact more closely involved than previously assumed. Researchers from Heidelberg, Tbingen (Gera number of) and Umea (Sweden) did this stunning discovery in a serial of complicated experimentations thale cress (Arabidopsis thaliana), a biological model organism. The international team of researchers, led by Jan Lohmann, stem cell biologist at Heidelberg University, have now published their results in the scientific journal "Nature". (Nature, 24. June 2010).</div><div style="text-align: justify;"><br />
</div><div style="text-align: justify;">Yet if certain basic definitions do not apply is it spoken of <u>plant hormones</u> or <i>phytohormones</i>. More Such limited people do also speak of <b>growth regulators</b>. In any case is no determined plant growth possible without them. <i>Plant hormones</i> are without exclusion small molecules. They are distributed within tissues from cell to cell, as in the case of auxin, via vascular bundles (as in the case of cytokinin), or via the intercellular space (ethylen).</div><div style="text-align: justify;"><br />
</div><div style="text-align: justify;">A list of outcomes show that <b>phytohormones</b> enter cells and influence intracellular action, though hardly anything about their intracellular dispersion or about their transfer from one compartment into another is identified. It continues open, too, whether they are stored in one or the other compartment, and whether they become biologically active by being set free from such compartments.</div><div style="text-align: justify;"><br />
</div><div style="text-align: justify;">The second messenger concept seemed not to work in plant cells. cAMP (cyclic AMP) was found in plants, but – beside some few exceptions – little is known about its function. Considerably clearer is that calcium ions as intercellular regulators.</div><div style="text-align: justify;"><br />
</div><div style="text-align: justify;">Usually display all known <u>plant hormones</u> a very high and complicated processes spectrum. In experiments occur some issues immediately after the application of a hormone, others take hours. It has been tried to resolve the fashion of action from such results. Presumptively are the activities of active enzymes or membrane attributes altered in fast reactions. In reactions with effects that become apparent only hours later is it likely that the gene expression (transcription or translation) is affected, though a complete chain of proof for the effect a <i>hormone</i> has on the molecular level, has in neither of these cases been furnished.</div><div style="text-align: justify;"><br />
</div><div style="text-align: justify;">Often does it seem as if specialization action were not operated just by a single substance, but by a complex, harmonious balance of simultaneously present regulator molecules and extern factors like light of a certain wave length, temperature, supply of nutriments, etc. In several cases exist indications that hormones mediate between an extern signal and a physiological activity (a cell’s response). <b>Plant hormones</b> act partially synergetic, partially antagonistic</div><div style="text-align: justify;"><br />
<div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-QEDImvIDUUA/TpCMcb8kHlI/AAAAAAAAAvY/5xmFKZ7nyO8/s1600/Plant_hormone.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="278" src="http://2.bp.blogspot.com/-QEDImvIDUUA/TpCMcb8kHlI/AAAAAAAAAvY/5xmFKZ7nyO8/s400/Plant_hormone.gif" width="400" /></a></div><br />
</div><div style="text-align: justify;"><u>Plant hormone</u> research has mostly been inhabited with the hormones themselves, their synthesis, their dispersion within tissues, their displacement, and their physiological effects. <i>Plant hormone</i> receptors, however, have received little attention. As a result can some of the observations not be interpreted conceptionally, which means that they hold just for certain plant species, may be contradictory to observations of other species, and cannot simply be transferred to different species.</div><div style="text-align: justify;"><br />
</div><div style="text-align: justify;">Numerous synthetically created growth regulators display hormone-like effects. They have a critical economic importance as herbicides or growth stimulators in modernised agriculture and horticulture, and due to their dangerousness and the toxicity of their by-products (dioxin!) – an explosive political potential.<br />
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</div>Andri F Martinhttp://www.blogger.com/profile/11669920311565328714noreply@blogger.com10tag:blogger.com,1999:blog-7580370865986271417.post-3539782876101137772011-07-22T06:49:00.000-07:002011-10-08T11:03:03.692-07:00PLANT TISSUE CULTURE INTRODUCTION<div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-D9cMYopszts/Til-0qPgnaI/AAAAAAAAAoo/OO2JOnEyRMU/s1600/Plant-tissue-culturejpg.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><br />
</a></div><div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-hZzDmo4nTWA/Til-ytJgK9I/AAAAAAAAAok/oKj9XqMsr6c/s1600/Plant_tissue_culture.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-hZzDmo4nTWA/Til-ytJgK9I/AAAAAAAAAok/oKj9XqMsr6c/s1600/Plant_tissue_culture.jpg" /></a></div><b>Plant Tissue culture</b> procedure were urbanized primarily to lobby the<i> totipotency</i> of conceal cells predicted by Haberlandt in 1902. <i>Totipotency</i> is the capacity of a conceal cell to do all the functions of development, which are characteristic of zygote, i.E., capacity to develop into a complete conceal. Hip 1902, Haberlandt reported culture of isolated single pole cells from leaves in Knop's salt solution enriched with sucrose.<br />
The cells remained alive in lieu of up to 1 month, increased in size, accumulated starch but futile to divide. Efforts to lobby <u>totipotency</u> led to the development of techniques in lieu of agriculture of conceal cells under defined conditions.<br />
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This was made feasible by the brilliant contributions from RJ. Gautheret in France and P.R. Colorless in U.S.A. Throughout the third and the fourth decades of 20th century. Most of the recent tissue culture media originate from the opus of Skoog and coworkers in the course of 1950s and 1960s.<br />
The principal rudiment culture, although crude, was completed by Hanning in 1904; he cultivated just about mature embryos of clear crucifers and grew them to maturity. The procedure was utilised by Laibach in 1925 to recover hybrid descendants from an inter-specific frustrate in Linum. Subsequently, assistance from several workers led to the maturity of this technique.<br />
Haploid plants from pollen grains were principal produced by Maheshwari and Guha in 1964 by culturing anthers of Datura. This striking the foundation of anther culture or pollen culture in lieu of the production of haploid plants.<br />
The procedure was expand urbanized by many workers, more notably by JP. Nitch, C. Nitch and coworkers. These workers showed to facilitate isolated microspores of tobacco deliver complete plants.<br />
<i>Plant protoplasts</i> are naked cells from which cell wall has been impassive. Hip 1960, Cocking produced portly quantities of <b><i>protoplasts</i></b> by using cell wall degrading enzymes.<br />
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<div class="separator" style="clear: both; text-align: center;"><a href="http://2.bp.blogspot.com/-D9cMYopszts/Til-0qPgnaI/AAAAAAAAAoo/OO2JOnEyRMU/s1600/Plant-tissue-culturejpg.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="133" src="http://2.bp.blogspot.com/-D9cMYopszts/Til-0qPgnaI/AAAAAAAAAoo/OO2JOnEyRMU/s200/Plant-tissue-culturejpg.jpg" width="200" /></a></div>The techniques of <b>protoplast</b> production bear nowadays been considerably refined. It is nowadays probable to stimulate entire plants from <i>protoplasts</i> and moreover to fuse <u>protoplast</u>s of atypical conceal species. Hip 1972, Carlson and coworkers produced the principal somatic hybrid conceal by fusing the <b>protoplasts</b> of Nicotiana glauca and N. Langsdorfii. Since at that moment many opposing somatic hybrids bear been produced.<br />
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A lucrative the system of corn cultures depended on the discovery in the course of mid-thirties of IAA (indole-3-acetic acid), the endogenous auxin, and of the role of B vitamins in conceal growth and in root cultures.<br />
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The principal continuously growing corn cultures were established from cambium tissue in 1939 independently by Gautheret, colorless and Nobecourt. The consequent discovery of kinetin by Miller and coworkers in 1955 enabled the induction of corn cultures from differentiated tissues. Shoot bud differentiation from tobacco pith tissues cultivated in vitro was reported by Skoog in 1944, and in 1957 Skoog and Miller future to facilitate root-shoot differentiation in this practice was regulated by auxin-cytokinin ratio.<br />
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The principal conceal from a mature conceal cell was regenerated by Braun in 1959. Development of somatic embryos was principal reported in 1958- 1959 from carrot tissues independently by Reinert and Steward.<br />
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Thus in a fill in punctuation mark,<b> the tissue culture techniques</b> bear made a extreme progress. From the sole objective of demonstrating the <i>totipotency</i> of differentiated conceal -cells, the procedure nowadays finds effort in both basic and useful researches in a run to of-fields of enquiry.<br />
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.Andri F Martinhttp://www.blogger.com/profile/11669920311565328714noreply@blogger.com0tag:blogger.com,1999:blog-7580370865986271417.post-63280524249535018932011-07-21T05:57:00.000-07:002011-10-08T10:58:17.612-07:00PLANT BIOTECHNOLOGY INTRODUCTION<div style="text-align: center;"><b> <span style="font-size: large;">PLANT BIOTECHNOLOGY INTRODUCTION</span></b></div><b><span style="font-size: large;"><br />
</span></b><br />
<b>BIOTECHNOLOGY INTRODUCTION</b><br />
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<div class="separator" style="clear: both; text-align: center;"><a href="http://3.bp.blogspot.com/-0uEDYQbjXA4/TikPjEQbUmI/AAAAAAAAAn8/VHrVwWuehnY/s1600/plant-Biotechnology.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="319" src="http://3.bp.blogspot.com/-0uEDYQbjXA4/TikPjEQbUmI/AAAAAAAAAn8/VHrVwWuehnY/s320/plant-Biotechnology.jpg" width="320" /></a></div><div style="text-align: justify;"><b>Biotechnology</b> is essentially the product of interaction between the science of biology and technology. The products of biotechnology are going to have a major impact on the quality of human life, productivity, trade and economics in the world. Already <i>biotechnology</i> is being used in the areas of diagnosis, prevention and cure of diseases, in the production of new and cheaper biochemical products e.g. pharmaceutical drugs, in enhanced production of new food resources, in environmental protection and energy conservation.</div><u>Biotechnology</u> is as old as human civilization and has been an integral part of the human life. Many scientists use the term <b>old or traditional biotechnology</b> to the natural processes that have been used since many centuries to produce beer, wine, curd, cheese and many other foods. The new or modern <b>biotechnology</b> includes all the genetic manipulations, cell fusion techniques and the improvements made in the old biotechnological processes.<br />
<div style="text-align: justify;">The term biotechnology was introduced in 1917 by Karl Ereky, a Hungarian Engineer. He used the sugar beets as the source of food for large scale production of pigs. Ereky defined <u>biotechnology</u> as “all lines of work by which products are produced from raw materials with the aid of living things”. </div><br />
<div style="text-align: justify;">The multidisciplinary character of <u>biotechnology</u> makes it rather difficult to define biotechnology. However there are several definitions available.</div><div style="text-align: justify;"><b>Biotechnology</b> is “the integrated use of biochemistry, microbiology, and engineering sciences in order to achieve technological (industrial) application of the capabilities of microorganisms, cultured tissue cells and parts thereof”.(European Federation of<i> Biotechnology</i>)</div><div style="text-align: justify;"><i>Biotechnology</i> is “the application of biological organisms, system or processes to manufacturing and service industries”.(British Biotechnologists)</div><div style="text-align: justify;"><u>Biotechnology </u>is “a technology using biological phenomena for copying and manufacturing various kinds of useful substances”.(Japanese Biotechnologists)</div><div style="text-align: justify;"><br />
</div><div style="text-align: justify;"><b>Biotechnology</b> is defined as “the controlled use of biological agents, such as microorganisms or cellular components, for beneficial use”. (US National Science Foundation).</div><div style="text-align: justify;">Biotechnology is the application of scientific and engineering principles to the processing of materials by biological agents to provide goods and service. (The Organization for the Economic Cooperation and Development (OECD), 1981)</div><div style="text-align: justify;">The application of biochemistry, biology, microbiology and chemical engineering to industrial process and products and on environment.(International Union of Pure and Applied Chemistry (IUPAC), 1981).</div><div style="text-align: justify;">A new definition after combining all aspects of biotechnology/genetic engineering was given by Smith in 1996- The formation of new combinations of heritable material by the insertion of nucleic acid molecules produced by whatever means outside the cell, into any virus, bacterial plasmid or other vector system so as to allow their incorporation into a host organism in which they do not naturally occur but in which they are capable of continued propagation.</div><br />
<b><i><u>PLANT BIOTECHNOLOGY</u></i> INTRODUCTION</b><br />
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<div class="separator" style="clear: both; text-align: center;"><a href="http://4.bp.blogspot.com/-qqQ9Y_itpG8/TikPzuwDypI/AAAAAAAAAoU/0TQ1NVB7FY4/s1600/Plant+Biotechnology.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="231" src="http://4.bp.blogspot.com/-qqQ9Y_itpG8/TikPzuwDypI/AAAAAAAAAoU/0TQ1NVB7FY4/s320/Plant+Biotechnology.jpg" width="320" /></a></div><div style="text-align: justify;">An important aspect of all <u>biotechnology</u> processes is the culture of either the plant cells or animal cells or microorganisms. The cells in culture can be used for recombinant DNA technology, genetic manipulations etc.</div><div style="text-align: justify;"><u>Plant cell culture</u> is based on the unique property of the cell-<u>totipotency</u>. CELL-TOTIPOTENCY is the ability of the plant cell to regenerate into whole plant. This property of the plant cells has been exploited to regenerate plant cells under the laboratory conditions using artificial nutrient mediums. With the advances made in genetic engineering, it became possible to introduce foreign genes into cell and tissue culture systems. This led to the development of GENETICALLY MODIFIED (GM) OR TRANSGENIC CROPS which had improved traits and characteristics.</div><div style="text-align: justify;"><br />
</div><div style="text-align: justify;"><b>History of cell culture</b></div><div style="text-align: justify;"><br />
</div><div style="text-align: justify;">In the early 19th century, Schleiden and Schwann proposed the concept of the 'cell theory'. In 1902, Gottlieb Haberlandt, the german botanist and regarded as the father of plant tissue culture, first attempted to cultivate the mechanically isolated plant leaf cells on a simple nutrient medium. He did not succeed in achieving the growth and differentiation of the cultured cells, however, he predicted the concept of growth hormones, the use of embryo sac fluids, the cultivation of artificial embryos from somatic cells, etc.</div><div style="text-align: justify;">During the period 1902 - 1930, attempts were made to culture the isolated plant organs such as roots and shoot apices (organ culture). Hanning (1904) isolated embryos of some crucifers and successfully grew on mineral salts and sugar solutions. Simon (1908) successfully regenerated a bulky callus, buds, roots from a poplar tree on the surface of medium containing IAA which proliferated cell division. Gautheret, White and Nobecourt (1934-1940) largely contributed to the developments made in plant tissue culture. White (1939) cultured tobacco tumour tissue from the hybrid Nicotiana glauca, and N. Langsdorffii. </div><div style="text-align: justify;">The period of 1940 - 1970s saw the development of suitable nutrient media to culture plant tissues, embryos, anthers, pollen, cells and protoplasts, and the regeneration of complete plants (in vitro morphogenesis) from cultured tissues and cells. In 1941, van Overbek and co-workers used coconut milk (embryo sac fluid) for embryo development and callus formation in Datura. Steward and Reinert (1959) first discovered somatic embryo production in vitro. Maheswari and Guha (1964) developed the anther culture for the production of haplid plants. Skoog and Miller (1957) advanced the hypothesis of organogenesis in cultured callus by varying the ratio of auxin and cytokinin in the growth medium. Muir (1953) developed a successful technique for the culture of single isolated cells wich is commonly known as paper-raft nurse technique (placing a single cell on filter paper kept on an actively growing nurse tissue). In 1952, the Pfizer Inc., New York (U.S.A) got the US patent and started producing industrially the secondary metabolites of plants. The first commercial production of a natural product shikonin by cell suspension culture was obtained. </div><div style="text-align: justify;">In 1980s using Genetic engineering, for the first time, it was possible to introduce foreign genes into cell and tissue culture systems to develop plants with improved characteristics (transgenic crops) which may contribute to the path towards the second green revolution.</div><br />
<a href="http://www.biotechnology4u.com/">Source </a>Andri F Martinhttp://www.blogger.com/profile/11669920311565328714noreply@blogger.com9