Study Questions_auxin_answered

Study Questions_auxin_answered - PLB112 summer 2009 Study...

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PLB112 – summer 2009 Harmer Study Questions Auxin signaling 1) What physical process underlies both the regulated elongation of growing plant cells and the opening of stomata? In both cases, water uptake drives a change in cell shape. For guard cells, an increased concentration of ions and organic molecules causes a decrease in water potential, which leads to an influx of water. In other cell types, stress relaxation in the cell wall (due to the action of proteins like expansins) allows turgor pressure to stretch the cell wall. 2) Define the following terms: hormone, IAA, phototropism, positive gravitropism, negative gravitropism, statolith, amyloplast, apical dominance. hormone - A chemical messenger produced in one cell or tissue that affects processes in another cell via binding to specific receptor. IAA – indole acetic acid, the most important auxin in plants phototropism – directed growth towards light positive gravitropism – growth in the same direction as the gravity vector, i.e. how roots respond to gravitropic stimulus negative gravitropism - growth in the opposite direction as the gravity vector, i.e. how shoots respond to gravitropic stimulus statolith – an organelle found within the specialized cells called statocytes that is responsible for sensing gravity. Statoliths are very dense and fall to the bottom of a statocyte in response to gravity. Amyloplast – a specialized plastid where starch granules are made and stored. Statoliths are a particular subtype of amyloplast. apical dominance – the ability of the main apical bud to suppress the development of lateral buds. Plants with a high degree of apical dominance have a tall central shoot and few lateral branches. 3) Name two differences between how plant hormones and animal hormones generally work. Animal hormones are usually made at one site and perceived elsewhere. In contrast, plant hormones can be made at several sites and can act there or elsewhere. Animal hormones usually bring about a specific response, whereas plant hormones tend to be very pleiotropic (they can cause multiple different responses, and may even have opposite effects in different organs). 4) What is/are the primary site(s) of auxin synthesis? How are auxins transported to other parts of the plant?
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PLB112 – summer 2009 Harmer Study Questions Auxin signaling Auxin is primarily synthesized at the shoot apex, mostly by young leaves. Auxin is transported throughout the plant via passive and active mechanisms. It is passively taken up by cells in its protonated form (via diffusion across the plasma
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This note was uploaded on 09/08/2009 for the course PLB 112 taught by Professor Hammer during the Summer '09 term at UC Davis.

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Study Questions_auxin_answered - PLB112 summer 2009 Study...

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