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Plant growth hormones, flowering, water relations

Plant growth hormones, flowering, water relations - Plant...

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Plant Growth Regulators Some terms: - phototropism: studying plant movements - differential growth: one side of coleoptile is longer than the other side - malt: when seeds are converted from starch to sugar - alpha amylase: enzyme created by aleurone in a barley seed that converts starch to sugar - “reporter” or bioassay system: method of discovering new growth regulators that involves tissue culture & placing it in a growth medium - callus tissue: pith that is disorganized and not differentiated - dormin : materials produced in scales of dormant buds - vivipary: no dormancy for seed and attached to the mother plant 4 Plant Growth Regulators: 1. Auxin 2. Giberellins/ Giberellic Acid/ GA 3. Cytokinins 4. Ethylene 5. ABA- Abscisic Acid Auxin : low molecular weight compound that has effects in very low concentrations 1. Apical Dominance: the main shoot apex inhibits lateral buds from growing out 2. Auxins are able to stimulate lateral reproduction (stimulate pericycle) 3. Stimulates division and differentiation in vascular cambium 4. Affects fruit development 5. “Leaf abscission” = leaf dropping 6. Photoperiod yields a reduction of auxin synthesis in the leaf Giberellins : product of rice fungus, but produced by all plants 1. Causes cell elongation 2. Stimulates flowering 3. Used commercially to stimulate increase in size of tissues (i.e.: grapes) 4. Controls state of maturity (favors youth). - “juvenile condition”: no flowers 5. Induces germination Bringing dormant seeds to germination using Giberellin: 1. Embryo releases GA 2. GA moves to aleurone layer 3. The aleurone makes & releases alpha amylase Cytokinins : stimulate cytokinesis/ cell division 1. Stimulates cell division 2. Delays senescence: death/aging 3. In mixtures with other growth regulators, in tissue culture, we can cause the callus to differentiate - high concentration of auxin + low concentration of cytokinins = roots - moderate concentration of auxin + moderate concentration of cytokinins= undifferentiated - low concentration of auxin + high concentration of cytokinins= shoots
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4. Can overcome apical dominance (can apply to axillary bud & it will grow out) 5. Causes tumors- increases cell division activity Ethylene : the most commercially important growth regulator - not transported through vascular system because it ʼ s a gas - triggers ripening in fruits - autocatalytic: can stimulate its own synthesis -
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