how do tannins protect plants and example of plant that uses them
bitter taste and toxic to insects. tea leaves contain them
how do alkaloids protect plants and example of plant that uses them
effects ingestors metabolism. plants that use them are coffee (caffeine which prevents germination of fungi and insects) and tobacco (nicotine)
how do terpenoids protect plants and example of plant that uses them
toxic - lemon grass uses them
how do pheromones protect plants
alert it's species to protect themselves
how do VOC's protect plants and plant that uses them
attract preadators preadator - cabbage
what does the mimosa padica do for protection
folds in leaves
where is auxin made
tips of roots and shoots in cells
how does auxin help plant growth
binds to receptors to lower the pH of the membrane to make it optimum temp for enzymes so the wall becomes very elastic so it can stretch more easily and grow
what is aptical dominance
where auxin inhibits the growth of lateral shoots and promotes growth upwards of the tip. lower conc of auxin at the bottom - so more lateral growth
how does auxin conc effect growth of plant
more auxin = more growth until max point where auxin inhibits the growth of a plant
experimental evidence for aptical dominance and plant growth effected by auxin:
when aptical shoot is removed: later shoots grow more at top. plant growth slows and comes to a stop.
process of abscission
- falling light levels means less auxin produced
- leaves produce ethane to switch on genes to produce enzymes that break down cell walls of separation zones.
- cells in seperation zones absorb water more easily and swell
- more strain of leaves and weakens protective layer
- petiole (stalk) breaks off and leaf falls off
effect of gibberellins
- stimulus seed germination by breaking down food stores to use to make ATP
- elongates plants by making the internodes bigger
experimental evidence for the effect of gibberellins
- varieties of plant grown with no gibberellins were less likely to germinate and grow short
- when fungi given gibberellins, they grew long and thin
auxin controlling stomata opening and closing:
soil water levels drop
plant roots produce ABA which is transported to leaves
binds to receptors on guard cells
changes ionic conc of guard cells reducing the water potential
tutor of cells reduces so stomata close
general structure of answer about 'how biotic stress' effects growth
less photosynthesis
less glucose
less respiration
makes less atp
less growth
what is phototropism
when plant bends towards unidirectional/unilateral light
what is geotropism
plants effected by gravity (eg roots are positively geotropic)
how does auxin control phototropism
allows more auxin down one side of the plant to elongate it so the plant bends
commercial uses of ethene:
to ripen fruit when u want it
commercial uses of auxin:
micro/propagation to make loads of identical plants
increases chnace of roots forming
weed killer - plant grows so much it's unsustainable and dies
what is micropropagation
growing identical plantlets in tissue culture and then planting them out
commercial use of gibberellins
delay ripening of fruit, and improve size and shape of yeild
commercial use of cytokinins
delay fruit aging, control propagation
synergism
working together
antagonism
opposing each other
auxins promote ..
cell elongation
gibberellins promote ...
stem elongation
apical
main stem
lateral
side branches
maintaining apical dominance
auxins favour growth of apical shoots, inhibiting growth of lateral shoots. lateral shoots near the top where auxins are, as you go down less auxins, so longer branches further down
2 types of tropism
phototropism and geotropism
tropisms
how plants respond to environment changes
geotropism
plants responding to orientation
phototropism
plants respond to light
negative phototropism
plant / roots bend away from light- follow gravity
how tropism inhibits growth
-fruit ripening
-abscission (leaf falls of stem)
what do gibberellins stimulate
pollen tube growth in fertilisation
how do gibberellins promote stem elongation
increase the length of internodes - beneficial to the plant as taller to reaching light