Module 5 - plant responses Flashcards
What is plant responses?
plants respond to changes in their environment in their environment to manage their chances of survival, e.g. towards the light to increase rate of photosynthesis
what is tropism?
the response to a plant to a directional stimulus
what are growth hormones?
- Plants response to stimuli using growth hormones
- as they have a circulatory system or a nervous systems like humans
What are auxins (IAA)?
they cause cell elongation in shoots (not cell division)
what are gibbrellins?
- they responsible for controlling flowering and germination
what are common about all growth hormones?
they are made in the growing regions of the plants - root tips and shoot tips
how do growth hormones move short distances?
- move short diffusion by diffusion and active transport
where do growth hormones move long distances?
in the phloem
what happens in phototropism?
IAA moves to the shaded side of the shoot/root
what happens in geotropism?
IAA always move to the underside
In shoots, what happens in phototropism?
IAA causes cell elongation, shoots grow towards the light
In roots, what happens in phototropism?
IAA inhibits cell growth -> roots grow towards the light
In shoots, what happens in geotropism?
- grow way from gravity, - - - cell elongation
- negative geotropism
In roots, what happens in geotropism?
- grow towards gravity
- Positive geotropism
Plant responses to herbitory - what happens when chemical are released?
- bitter/bad tasting
-toxic
Plant responses to herbitory - example of a chemical
- Tannins -> toxic -> Inhibit enzyme in insects
- Alkeloids e.g. caffeine and cocaine
- attract herbivores - attract wasps to eat caterpillars
Plant responses to herbitory - give examples of sting or thornes
e.g. stinging nettles such as roses
Plant responses to herbitory - how does folding leaves work?
- folds leaves in half quickly
- dislodge small insect herbivores
Plant responses to herbitory - example of folding leaves?
mimosa
explain the steps of apical dominance?
- Apical bud at the top of the stem produces auxin e.g. IAA
- auxins promote growth at the apical bud
- auxin inhibits growth of the lateral buds
- plant grows taller and doesn’t compete with itself
- apical bud is dominant over lateral bud
- auxin concentration decreases with distances from apical bud -> lateral buds further from apical bud are less inhibited
what happens if we remove the apical bud?
-if the apical bud is removed, less auxin is made
- lateral buds are not inhibited
-> start to develop
- becomes bushy
- if auxin is added to top of of cut stem
- apical dominance continues
what are an example of auxins?
IAA
Give an example of gibrellins ?
Gibbrellic acid
where are auxins made?
- root tips
- shoot tips
- young leaves
- growing parts of the plants
where are gibrellins made?
- seeds
- young leaves
where is ethene made?
- old leaves
- ripening fruit
give an example of absiisic acids?
ABA
what causes growth of auxins?
- growth in shoots by cell division
what promotes gibrellins?
- seed germination
- flowering
- stem elongation
- lateral shoot growth
what promotes ethene?
- leaf loss/drop
- fruit ripening
what promotes Abscissic acid?
- closing stomata
what inhibits auxins?
- growth in root tips
- leaf loss
what inhibits abscissic aicd?
- gibrellins (seed germination)
what is the commercial use of auxins?
- rooting powders
- weed killers
what is the commercial use of gibrellins?
seedless grapes
what is the commercial use of ethene?
- ripen demands in supermarkets
what is the commercial use of abscissic acid?
reduces drought stress
What happens in stomata closure?
- stomata closes to secure water (transpiration)
- guard cells turgid - open
-ABA binds to receptors in guard cell membrane - open calcium and potassium channels
ions diffuse out of guard cells - increases water potential of guard cells
water will leave the guard cell by osmosis - flaccid - stomata closes
explain leaf loss by ethene?
- old leaves make ethene
- causes layer of cells in stalk of leave to expand and break
- leaf falls
- water and nutrients
Explain seed germination?
starch is hydrolysed into glucose in seeds
- glucose is respired (ATP)
- seeds can germinate
