plant responses (ie tropisms)

stimulus

a change in the internal or external environment

stimuli are detected by…

receptors

responses are produced by …

effectors

what is the benefit of organisms responding to stimuli

it increases their chance of survival

what are tropisms

growth responses controlled by a directional stimulus

tropism relating to light

phototropism

tropism relating to gravity

gravitropism

what is the hormone that controls cell growth

indoleacetic acid (IAA)

where is IAA produced

tips and shoots of flowering plants

in the presence of light

IAA moves towards the shaded portion

cells on this side are elongated

shoot bends towards the light

in the presence of gravity

IAA builds up on the lower side of the root

cell growth on this side is inhibited

root bends downwards