BSC 2011 Chapter Notes - Chapter 39: Seed Dormancy, Thigmotropism, Auxin
27 Aug 2016
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Tropism: a plant growth response from hormones that results in the plant growing either towards or away from stimulus, hormones: chemical messengers that coordinate the different parts of a multicellular organism. Types of tropism: phototropism: growth towards or away from light, gravitropism: growth towards or away from gravitational force, thigmotropism: growth towards or away from touch. Positive vs. negative tropism: positive is growth towards a stimulus. Positive thigmotropism: growth towards a tactile stimulus: negative is growth away from a stimulus. Replace the above terms with negative and away. Cause proton pumps to activate > lower ph > weakening of the cell wall > turgor pressure expands and elongates cell wall. High concentrations of synthetic auxins kill certain plants (usually weeds). Synthetically produced auxins in high concentrations = herbicides: cytokinins: stimulate cell division or cytokinesis. Proper ratio of auxins & cytokinins leads to cell division and differentiation: gibberellins: work with auxins to stimulate stem elongation.
