AEBI 210 Lecture Notes - Gravitropism, Heliotropism, Auxin
8 Jan 2013
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Document Summary
A plant curves towards the light because of elongation on shaded side by auxin. Auxins increase growth in shoots, and reduce it in roots. Sedimentation of amyloplasts (starch with plastids) helps gravity perception. More auxins on outer side of vine causes elongation. Flowers and leaves move from east to west facing to get the sun"s direct rays. Pulvinus cells at the base of leaves cause through change in turgor pressure. Leaf and petal movements, opening of stomata, fragrance emission, metabolism. Leaves move outward in the day and up towards the stem at night. Response to the relative period of light (or darkness) Plants can flower when days are short or long, or be unaffected. Phytochrome ( either pr or pfr) is a photoreceptor that detects day/night transitions. Pfr promotes flowering in long-day plants and inhibits it in short-day plants. Movements occurring in plants independent of the stimulus position. Tactile stimuli, perhaps in defense of herbivores or predation of an insect.
