taxes, kinesis and tropism

what is a tropism

response of a plant to a directional stimulus

positive = towards

negative = away

where is IAA synthesised

in the tips of roots and shoots

how does IAA control growth

cell elongation

the concentration of IAA determines

the rate of cell elongation within the region of elongation

when a plant grows towards the light its called

positive phototropism

in shoots higher concentration of IAA results in

greater rate of cell elongation, plant bends towards the light

when the root grows towards gravity

positive geotropism

in roots higher concentration of IAA results in

lower rate of cell elongation

Taxes and kineses are simple responses that

enable mobile organisms to stay in a favourable environment

kinesis is

non directional response to stimulus, rate of movement is determined by intensity of stimulus

taxis is

directional response to a stimulus, organism moves directly away from or towards the stimulus

example of woodlice kinetic response

in high humidity they move slowly and turn less often to stay in that favourable environment, less humid move faster and turn more often so they move into a new area