Explain any four tropu movement that occur in plant
Answers
Phototropism
Plants grow towards or away from the light, the type of tropism in the response to light is called phototropism. In general, the stems usually show positive phototropism, while roots show negative phototropism. Leaves also positively respond toward the source of light.
Gravitropism
It is a type of tropism where plants show some growth in response to gravity. Stems are negative to the gravitropism while roots are positive to the gravitropism. This is also referred to as geotropism. Among different parts of plants, the primary roots and certain other portions of the root system show positive geotropism by growing directly towards the centre of gravity. The stems are called as the negatively geotropic as they grow away from the centre of gravity. The leaves are transversely geotropic as they select their positions at right angles to the centre of gravity.
Chemotropism
There are few chemical substances, which are actively responsible for bringing a curvature movement in plant organs. When plants grow in response to certain chemicals, this type of response is known as chemotropism. Few examples of chemotropic movements are the conversion of a flower into fruit, the growth of a pollen tube down the style during fertilization, movement of tentacles in Drosera, etc.
Thigmotropism
The growing or developing movements made through plants in response to contact with a solid object are called thigmotropism. These type of movements are usually seen in tendrils and twiners. This movement is also referred to as Haptotropism.