plant hormones Flashcards
state 3 reasons that suggest plants are dynamic systems
- photosynthesis
- produces food
- responds to environmental stressors
what are key limitations of plants
- rooted (non mobile)
- don’t have a rapidly responding nervous system
what is the general role of plant hormones?
produced in one region of a plant, transported through transport tissues between cells
- have an effect in another plant region
state 2 reasons plants produce chemicals
- protect themselves against insects
- chemical defence against herbivores
state 4 examples of plant hormones
- auxins
- ethene
- gibberellins
- abscisic acid
describe the role of auxins
- causes cell elongation in stems
- inhibits growth in roots
- prevents leaves dropping
- maintains apical dominance
describe the role of ethene
- gas that causes fruit to ripen
describe the role of gibberellins
- stimulates seed germination, stem elongation and pollen tube growth in fertilisation
describe the role of abscisic acid
- stimulates stomatal closing
- maintains dormancy of seeds
state 3 commercial uses of plant hormones
- control fruit ripening
- rooting powders
- hormonal weed killers
describe control of fruit ripening
- ethene is used to speed up fruit ripening
- restricting ethene can delay ripening
- low O2, high CO2 and low temp prevent ethene synthesis
describe rooting powders
- synthetic auxins are used
- stimulates growth of roots from cut stems
- used to encourage cuttings to make roots
describe hormonal weed killers
- synthetic auxins used
- kill broad leaved weed in fields of monocots
- increases growth rate of weeds
- weeds are unable to absorb nutrients and energy from surroundings to keep up with growth rate so they die
what is the experimental evidence for the role of auxins
- auxins produced in the plant apex inhibit growth from lateral buds
- if the tip is removed the plant grows from the buds
- known as apical dominance
summarise the experiments for the roles of auxins
- auxin paste was applied to a cut shoot and lateral buds did not grow
- auxin transporter was applied below apical tip and this allowed natural growth which suggests that low levels of auxins allow lateral growth
- auxin conc increases in lateral buds when apical tip is removed
summarise the experiments for the roles of gibberellins
- gibberellins applied to dwarf plant varieties - they grew taller - gibberellins caused stem elongation
- tall pea plants had higher conc of gibberellin
what is the commercial role of auxins
production of seedless fruits
what are the commercial roles of gibberellins
- delay ageing and ripening in fruit
- improve size and shape of fruits
- beer brewing to speed up malting process
what is the commercial role oc cytokinins
- prevent ageing of ripening fruit and products (eg. lettuce)
- micropropagation to control tissue development
what is the commercial role of ethene
promotion of fruit dropping
- eg. cotton, cherries, walnuts
