plant responses

• harbivoury plant protection: chemical examples


  tannis

  alkaloids

  terpenoids

  pheromones

  VOC
• 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