Week 10, Lecture 1, Plant Hormones

Week 10, Lecture 1, Plant Hormones - Plant hormones Five...

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B I O L O G Y 1 2 2 3 Hormones and Plants Chapter 31 Plant hormones • “Hormone” was first used to describe substances in animals – “a substance produced in a gland that circulates in the blood and has an effect far away from the site of production” • In plants used to mean a compound that acts at low concentrations to affect growth and development. Plant Hormones • Many parallels between plant and animal hormones • Naturally occurring organic substances that profoundly influence physiological processes at low concentrations • Site of synthesis and mode of transport is different 14-Mar-10 Gardiner 3 Plant hormones • Five plant hormones known by the mid 1960s, new compounds called plant growth regulators • The five hormones –A u x i n s – Cytokinins – Gibberellins – Ethylene (ethene) – Abscisic acid • Other plant growth regulators – Brassinosteroids – Salicylic acid – Jasmonic acid –S y s t em i n General plant hormones General plant hormones ± Auxins ± Gibberellins ± Cytokinins ± Abscisic acid ± Ethylene Seven Classes of Hormones Table 31.1
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Auxin Auxin Tryptophan Auxin • Quintessential plant hormone • Principal role in enlargement of plant cells • Synthesized in meristematic regions 14-Mar-10 Gardiner 8 Auxin • Mainly indole acetic acid (IAA) • Indole acetic acid and related molecules • Photo-and gravitropism • The shoot hormone, made in the shoot apex • Promote elongation of cells in coleoptiles and stems • Travels down the stem – Polar Auxin Transport The Darwins’ Experiments on Phototropism Fig. 31.3 Fig. 31.3 Opaque cap Light Light Translucent cap Fig. 31.4 3 Went then placed the agar block containing auxin on another detipped oat shoot, and the shoot resumed elongation, growing about as rapidly as in a control seedling with an intact shoot tip.
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This note was uploaded on 04/18/2010 for the course BIOLOGY 1223 taught by Professor Gardiner/lajoie during the Fall '09 term at UWO.

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Week 10, Lecture 1, Plant Hormones - Plant hormones Five...

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