Lecture 19 Flashcards
what are the functions of plant hormones
stimulation, inhibition, occur in inactive forms, may change sensitivity to hormones
what are the classic five plant hormones
auxins, cytokinins, ethylene, abscisic acid, gibberellins
what was the first plant hormone to be discovered
auxins
how were auxins discovered
the Darwins observed phototropism (bending towards light)
what are the role of auxins
differentiation of vascular tissue as plant develops and in healing, induction/arrangement of leaves, chemical signals, formation of lateral and adventitious roots, fruit development
what do cytokinins do
found in tissues, actively dividing seeds, fruits, leaves, and root tips, transported via xylem from roots
how can the cytokinin/auxin ratio affect the plant
more auxin= elongation and differentiation in roots; more cytokinin= elongation and differentiation in buds
what is the function of ethylene
to aid in overcoming obstacles, may inhibit cell expansion, may also promote cell expansion, may cause aerenchyma formation
how does ethylene help cucurbitaceae
promotes sex expression, ethylene stimulates female flowers in monoecious plants
how do gibberellins help cucurbitaceae
they stimulate male flowers
what is the function of abscisic acid
prevents seed germination, root to shoot signal (control stomatal closure, mutants without ABA wilt)
where are gibberellins found
very high levels in developing seeds, lower levels in young leaves, buds, upper stems
what are the functions of gibberellins
make dwarf mutants grow tall, breaking seed dormancy and germination, can cause bolting and affect fruit development
