plant responses Flashcards
(14 cards)
role of auxins
cell elongation, prevents absission/leaf fall, apical domince, troposins
role of gibberelins
flowering, stem elongation, mobalisation of food in seed germination, stimulate pollen tube growth for fertilisation
role of ethene
causes freuit ripening, promotes absision in decidious plants
role of ABA abscisic acid
maintains dormacy of seeds and buds, stimulates antifreeze, stimulates stomatal closure
mechanisms of gibberelins in seed germination
when seeds absorb water embryo is activated and begins to produce gibberelins. gibberelins stimulate synthesis of enzymes eg amylase (starch to maltose) to break down starchy stores fround in the endosperm
mechanisim of auxins - apical domiece
as it diffuses down from the meristematic cells it binds to receptors that causes the cell walls to decrease in ph 4 Current model: Auxin molecules bind to specific receptor sites in the plant cell membrane, activating
process which pumps hydrogen ions into cell wall spaces, lowering pH to about 5, the optimum pH for
the enzymes that break down bonds between cellulose microfibrils, so they slide past each other
easily and the walls remains very flexible and plastic allowing cells to stretch and grow (
followed by increased rate of shoot elongation appears to confirm both change in pH and resulting increase in stretching of
cell wall and growth (1).
auxin mechanisms not aprical domince
- supress lateral shoots at high concs. at low auxin conc root growth is stimulated
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synergism and antagonism
complementary synergenic
opposites, antagnostic the other inhibits the other
leaf drop in deciduous plants is a response to
abiotic stress, daily sunlight hours, temp
how does antifreeze work in plants
cytoplasm and sap in vacules contain solutes that lower the freezing point
mechanisms of stomatal closure
- ABA produced in roots when water availability is low
- aba binds to cell membrane of guard cells which triggers influx of calcium ions that trigger K+ ions to leave the cell, raising the the water potential of the cell so water leaves via osmosis leaving the cell flaccid and the stomata closed
plant responses to herbivory 1,2,3,4
- physical defences, thorns, spikes,
- chemical defences
- tannins, bitter and toxic
- alkaloids, bitter nitrogenous- drugs eg caffine, tobacco
- terponoids, essential oils eg mint lavendar- often toxic to fungi antifungal and antibacterial - pheromones
chemial that affects behavior of another
eg. signal to other plants to produce callose - folding in respponse to touch thigmatropism
Cytokinins
Cytokinins are plant hormones, primarily synthesized in the roots, that promote lateral shoot growth and delay leaf senescence. They work in opposition to auxin, which promotes apical (main stem) growth and inhibits lateral growth.
flowering and fruit development
tropisms
auxin
shoot:
positivley photo
negativley geo
root:
positivley - geotropic
negativley - phototrophic
