| Plant Responses to Internal and External Stimuli; Bio notes for Chinaman. | |
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| Tweet Topic Started: Feb 25 2009, 06:59 PM (371 Views) | |
| Danny Keen | Feb 25 2009, 06:59 PM Post #1 |
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You'll have to bear with me, since this doesn't double-indent when making lists. Also, I italicized the stuff he told us was very important, and he wants us to know the comparisons and contrastisons between the hormones. Plant Hormones * Hormone: chemical signals for coordination * Tropism: Moving towards or away from stimuli Differs from taxis, since taxis entails moving the entire body. - Gravitropism and thigmotropism * Auxin - Located in seed embryos, meristems of apical buds, young leaves - Function: stem elongation, root growth, differentiation, budding, fruit budding, apical dominance, tropisms * Cytokinins - Zeatin * In roots * Root growth & differentiation, cell division & growth, germination, delay senescence (aging), apical dominance (w/ help from auxin) * Giberellins - GA3 * In meristems of apical buds & roots, young leaves, embryos * Germination of seed & bud, stem elongation, leaf growth, flowering (bolting), fruit development, root growth & differentiation * Abscesic acid (ABA) - In leaves, stems, roots, green fruit - Inhibits growth, closes stomata during stress, counteracts breaking of dormancy - Facilitates maturation * Ethylene - Gaseous hormone - In ripening fruit tissue, stem nodes, aging leaves & flowers - Ripens fruit, opposes auxin (I can't really read my notes right here, and some of it doesn't make sense), involved in growth and development of roots, flowers, & leaves, role in senescence Daily and Seasonal Responses * Circadian rhythms (24-hour period) * Photoperiodism (phytochromes) * Short-day plant: light period shorter than critical length to flower, flowers in fall, winter, and late summer; poinsettia and chrysanthemum * Long-day plant: light period longer than critical length to flower, flowers in spring and early summer; spinach, radish, lettuce, iris * Day-neutral plant: unaffected by photoperiod (tomato, rice, dandelion) * Critical night length controls flowering Phytochromes * Plant pigments measuring length of darkness in a photoperiod - Pr: red absorbing (660 nm) - Pfr: far red absorbing (730 nm) * Red light shortens the dark period * Far red negates the red light (I'm guessing it also lengthens the dark period or something, I dunno) That's where we stopped. |
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