30: plant hormones Flashcards
plant hormones
chemical signals that modify or control specific processes
what type of concentrations are plant hormones produced in?
low concentrations
3 steps to hormone response?
- reception
- transduction
- response
the 5 major plant hormones
- auxin
- cytokinin
- gibberellins
- abscisic acid
- ethylene
auxin
to grow or increase vertically (apical dominance)
cytokinin
stimulates cell division, and promotes apical dominance w/ auxin
gibberellins
to expand rapidly, plants become too tall and yellow - involved in cell elongation
abscisic acid
slows growth and can signal:
- seed dormancy
- drought tolerance
ethylene
for stress/ ripening - breaks down cell wall and is released (yellow bananas release more ethylene)
primary site of auxin synthesis?
SAM, and young leaves
polar transport of auxin plays a role in what?
pattern formation of roots and leaves
responses to low vs. high auxin?
high: herbicide
low: great for root growth
where is cytokinin produced?
in actively growing tissues like roots, embryos, fruits
why do plants become bushier if a terminal bud is removed?
auxin is found in the main shoot, so cutting it down activates axillary buds active
3 things required to break seed dormancy?
- water
- light
- heat
which hormone controls seed dormancy and germination?
gibberellin
which hormone is the primary signal that enables plants to withstand drought?
abscisic acid
precocious (early) germination can be caused by?
inactive or low levels of ABA
what happens to stomata during ABA accumulation?
they close rapidly to prevent water loss
leaf abscission
when leaves start to fall off trees
what is the programmed death of cells or organs?
senescence
