BIO_SC 1200 Lecture Notes - Lecture 1: Auxin, Phototropism, Thigmotropism
15 Jan 2015
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Plant hormones are called phytohormones: 5-13 control many processes in plants. Range due to scientific debate and different plants using different hormones: debate is over what counts as a hormone, gene expression controls hormone levels and vice versa, mostly made in the meristems, then transported throughout the plant. Can be made in any cell, but those hormones are made where used. Auxin first hormone to be identified in 1926: primary growth regulator. Low concentration promote root growth: high concentrations inhibit it. Causes growth through cell elongation: loosens cell wall so the vacuole pushes out, expanding the cell, helps plants adjust to environment. Controls phototropism, gravotropism, and thigmotropism (growth effected by touch or contact) Phototropism: auxin is shuttled to the side of the plant facing away from light, causing those cells to elongate and bends the stem towards the light. Gravotropism: auxin collects in the bottom of the tissue, whether it be stem or root.
