Tropic movements
Plant movements that take place along a particular direction are called Tropic movements.
These movements can be towards the direction of the stimulus or away.
The stimulus can be gravity, light, chemicals etc.
Consider this example again;
Here, the roots grow in the direction of gravity (downwards), this is Positive Geotropism
- Positive; since the movement is towards stimulus
- Geotropism; movement due to gravity
On the other hand, shoot grows upwards opposite to the direction of gravity, this is Negative Geotropism
- Negative; since the movement is away from stimulus
- Geotropism; movement due to gravity
Example of Phototropism:
Sunflowers grow towards the sunlight
Example of Chemotropism:
Growth of pollen tubes towards ovules in the process of reproduction in plants
Example of Thigmotropism:
Plant tendrils clinging on to a support and growing
Example of Hydrotropism:
Plants grow towards regions of having water if there is a source of water nearby
Example of Thermotropism:
The plant responds to changing temperature and the growth is impacted.
The leaves of Rhododendron start folding in cold temperatures.