Survival and responses in plants
Plants need to respond to stimuli too. Flowering plants, like animals, increase their chances of survival by responding to changes in their environment.
E.g. they can sense gravity, so their roots and shoots grow in the right direction.
They can sense the direction of light and grow towards it to maximise light absorption for photosynthesis. Climbing plants have a sense of touch, so they can find things to climb and reach the sunlight.
A tropism is a plant’s growth response to an external stimulus. A tropism is the response of a plant to a directional stimulus (a stimulus coming from a particular direction). Plants respond to stimuli by regulating their growth. A positive tropism is a growth towards the stimulus. A negative tropism is growth away from the stimulus.
Phototropism is the growth of a plant in response to light. Shoots are positively phototropic and grow towards light. Roots are negatively phototropic and grow away from light.
Geotropism is the growth of a plant in response to gravity. Shoots are negatively geotropic and grow upwards. Roots are positively geotropic and grow downwards.
Responses are brought about…