Plant Hormones Flashcards
Auxins
Control cell elongation
prevent leaf fall
maintain apical dominance
Stimulate release of ethene
Gibberelins
Stem elongation
Trigger seed germination
Stimulate pollen tube growth in fertilisation
Ethene
Fruit ripening
Abscission
ABA abscisic acid
Dormancy of seeds and buds
Antifreeze production
Stomata closing
Seed germination
Seed absorbs water embryo activat produce gibberelins - stimulate enzymes to break down food stores
Produce atp to grow
Apical dominance
High conc of auxin supresss lateral shoots
Growth at tip in main shoot
Inhibits lateral shoots
Low conc of auxin promotes root growth
Auxin func
Synthesised in meristem
Diffuse from tip
Low pH develops
Vacuoles bigger and cell wall stretches
Cell wall becomes rigid auxin is destroyed no cell elongation
Gibberelin func
Elongation of plant stems between internodes
Removal of gibberelins
Dwarf plants
Stems shorter reduce waste and vulnerability to damage by weather
Synergism
Hormones working together eg auxins and gibberelins
Antagonism
Hormones having opposite effects
Eg gibberellins and abscisic acid
Abscission
Lengthening of dark periods cause abscission - dormancy
Falling conc of auxins trigger ethene production - switch on genes in cell to stimulate enzyme production digest separation layer
Vasc bundles sealed off and fatty deposits form protective layer
Stomata control
ABA release under abiotic stress when water falls
Changes in ionic conc of guard cells incr turgor of cells closing stomata
Chemical defences
Tannins- phenols bitter taste and toxic to insects
Alkaloids - affect metabolism and poison animals eg caffeine toxic to fungi
Terpenoids- toxins that interfere w animals eg pyrethrin interferes w nervous sys of insect
Pheromones
Chemical which effects behav of other members of species
Pheromone which absorbed by other leaves trigger production of callose
Communicate w neighbour via roots
Signals larger predators VOC - cabbage and wasps, apples and mites
