CH.27/28 Plant Hormones/External Factors Flashcards
Roles of Auxin
Cell elongation, apical dominance, lateral root formation, tropisms
Roles of Ethylene
Promote leaf/fruit abscission, cause fruit ripening
Roles of Abscisic Acid
prevents premature seed germination, induces stomatal closing
Roles of Gibberellins
stimulates cell elongation+division, hastens seed germination
stimulates cell elongation+division, hastens seed germination
Roles of Brassinosteroids
steroid hormones in plants that have a variety of effects, including cell elongation, retarding leaf abscission, and promoting xylem differentiation.
Tropism
A growth response of a plant toward or away from a stimulus
Gravitropism (roots)
Growth towards (positive) gravity; amyloplasts sense gravity at bottom of cell, auxin inhibits elongation on lower side of cell
Gravitropism (shoots)
Growth away (negative) from gravity, auxin promotes elongation on lower side
Hydrotropism
a plants growth response to water; root grows towards the water
Thigmotropism
A growth response to touch
Nastic movement
Response of plant to stimulus; its direction of growth is independent of stimulus; can be due to turgor pressure
Sleep mvmts = leaves droop at night (turgor pressure)
Helitropism
tropism + nastic movement; tracking of sun via turgor pressure
Photoperiodism
Flowering response due to changes in day length
circadian rhythm
24hr clock reset by phytochrome system, helps plant tell what time of day
Phytochrome
responsible for photoperiodism
Pr= inactive, absorbs red light, converted to Pfr
Pfr= active, absorbs far red light, converted to Pr
Pr=Pfr during day, flashes of far red light at night will reverse flowering behavior
