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chapter38 - plant hormones _shortened_

chapter38 - plant hormones _shortened_ - Chapter 38...

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Chapter 38
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Growth of a plant in the direction of its light source: blue light (<500nm) photoreceptors (phototropins) hormonal signal (auxin) shoot bends toward light (+) Positive growth response to touch mechanical stimulus hormonal signal (causing twining or curling) e.g. production of tendrils e.g. vine (leaves); Drosera and the Venus Flytrap (trichomes) Thigmotropism Video…………
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Growth in response to gravity: Most stem tips grow away from earth’s center ( negative gravitropism) redistribution of auxins, elongation of cells in root tip due to acidification Most root tips show positive gravitropism (NB: root cap removal) amyloplasts in root parenchyma cells collect at bottom of root cap. So that regardless of orientation stem up, root down (root cap)
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Phytohormones are organic compounds produced by plants <10 (-6) mol/l (uM) Act as highly specific chemical signals Auxin elicits responses that regulate growth & development : Transcription of certain genes Acidification of cell walls Same mechanisms for other hormones
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