Plant hormones Flashcards
hormones
signaling molecules carry info from cell to cell
Auxins
lengthen shoots and apical dominance
- decrease abscission/leaf dropping
- fruit formation
Ethylene
ripen fruit (is a gas)
ABA
Abscisic Acid – induce dormancy
- drought tolerance by
closing stomata
Positive feedback loop with fruit ripening
one fruit ripens ethylene gas released into air recieved by other fruits near by other fruits ripen increase stimuli repeat
seed dormancy
mature seed produces ABA
1. induces production of proteins to resist dehydration
2. induce seed dormancy
(Stop growing, block mitosis, uses way less energy)
in order to germinate (get out of dormancy)
ABA levels must come down
- heavy rain washes ABA out of seed
- light and cold exposure may also be needed
Auxin concentrations control
gene transcription (what gene is activated)
genes controlled regulate
cell differentiation
Auxin only produced in the
apical meristem
Auxin is transported down the shoot by
Polar transport (much faster than diffusion)
Apical meristem =
tip of root/shoot that is growing : doing mitosis
why is auxin mechanism polar
Polar because auxin transport proteins are only located at the base of the cells.
(at one pole
Acid Growth
Hypothesis
High concentration of Auxin cause elongation of apical cells (growth)
why called acid growth hypothesis
Called Acid Growth because high Auxin conc. causes protein pumps to actively transport H+ out of the cell (making the cell wall low pH)
Effects of high H+ conc. in cell wall
Membrane potential created (voltage across memb.) Memb. Pot. Induces ion uptake by cell Cell becomes hypertonic Osmosis increases turgor pressure Low pH Activates expansin :
expansin
Enzymes that break crosslinks (H-bonds) btwn cellulose fibers
Allows cell wall to expand
cell growth based on light
Under uniform light cells grow equally
Directional light causes dark side cells to elongate more
