describe the various types of tropic movements found in plants
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Tropic movements
When a plant shows some growth movement in response to a stimulus, it is known as tropism. Tropism is a direction, which is specific and depends on the direction of the stimulus. Plants may either show a positive or negative movement as a response to a stimulus. If the movement is towards the direction of stimuli, it is known as positive tropism, if the movement is away from the stimuli, it is known as negative tropism. Discussed below are a few types of tropism.
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 the gravity. Stems are negative to the gravitropism while roots are positive to the gravitropic. This is also referred to as geotropism. Among different parts of plants, the primary roots and certain other portions of the root system show positively geotropic by growing directly towards the center of gravity. The stems are called as the negatively geotropic as they grow away from the center of gravity. The leaves are transversely geotropic as they select their positions at right angles to the center 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 chemotropism 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.
Hydrotropism: The movement or the growth of a plant in relation to the stimulus of water are called hydrotropic movements and the equivalent response to the stimulus of water is called hydrotropism. In this type of movement, roots show the positive hydrotropic response, as they move and grow towards the water.
Thermotropism: It is the form of a tropic movement in which a plant or a part of the plant respond to the changing atmospheric temperature. For example, this type of movement is usually seen in the plants of Rhododendron. Here leaves starts twisting or bending in response to cold temperatures.
These are the six different types of tropisms which help plants to be more adaptive and help in their survival. The positive response of stems towards light helps plants in photosynthesis and the positive response of roots towards the gravity helps in the absorption of minerals and water from the soil.
Movement of plant towards stimuli is called tropic movement. It can be in the direction of the stimuli or away from the stimuli.
1. PHOTOTROPISM :-
The movement of plant towards light is called phototropism.
Ex :- Take a plant and put it near the window then you see that it's stem moves toward in the direction of light showing + ve phototropism and roots show - ve phototropism.
2. THIGMOTROPISM :-
Movement of plants toward chemicals is called thigmotropism.
Ex :- Coiling of plants.
3. CHEMOTROPISM :-
Movement of plants toward chemicals is called chemotropism.
Ex :- Growth of pollen tube towards ovule.
4. HYDROTROPISM :-
Movement of plants toward water is called hydrotropism.
Ex :- Growth of tomato roots in the direction of water then it's root shows + ve hydrotropism and stem shows - ve hydrotropism.
5. GEOTROPISM :-
Movement of plants toward earth is called geotropism.
Ex :- Take a portaid plant and put it horizontally towards earth then it's root shows + ve geotropism and stem shows - ve geotropism.