Demonstrate experiment to show
A phototropism
B.geotropism
C.chemotropism
D.hydrotropism
Demonstrate experiment to show
A phototropism
B.geotropism
C.chemotropism
D.hydrotropism
1. Demonstration of Phototropism in Stem:
Take a potted seedling of a plant. Place it in heliotropic (phototropic) chamber with a small hole on one side (). Close the top of the chamber. Place it in a position that allows sufficient light to pass through the hole. Keep it there for a couple of days. Open the chamber and observe the seedling. It shows a bending (curvature) of the stem towards the hole (direction of light stimulus). This response is positive phototropism.
2. Demonstration of geotropism in a plant:
Take a potted seedling. Place it horizontally within a dark wooden chamber (). Open the chamber after one day. The stem will be seen bent upwards, i.e., in a direction opposite to the pull of gravity. This is negative geotropism. Take the roots out of the pot. They will show a curvature or bend opposite to the bend of the stem. This curvature is in the direction of the pull of gravity. It is positive geotropism.
Chemotropism: Certain chemical substances are responsible to bring about curvature movements in plant organs. For instance, movement of Pollen tube towards ovary due to absorption of calcium and borate from style of carpel; movement of tentacles in Drosera, closing of lid of Nepenthes due to nitrogenous food, and penetration of haustoria of parasite into host body etc.
Hydrotropism: The paratonic curvature movements of growth in relation to the stimulus of water are called hydrotropic movements. The tropic response to the stimulus of water is called hydrotropism. The roots show positive hydrotropic response, i.e., they bend towards the water ). Hydrotropism is stronger in roots compared to geotropism.
1. Demonstration of Phototropism in Stem:
Take a potted seedling of a plant. Place it in heliotropic (phototropic) chamber with a small hole on one side (). Close the top of the chamber. Place it in a position that allows sufficient light to pass through the hole. Keep it there for a couple of days. Open the chamber and observe the seedling. It shows a bending (curvature) of the stem towards the hole (direction of light stimulus). This response is positive phototropism.
2. Demonstration of geotropism in a plant:
Take a potted seedling. Place it horizontally within a dark wooden chamber (). Open the chamber after one day. The stem will be seen bent upwards, i.e., in a direction opposite to the pull of gravity. This is negative geotropism. Take the roots out of the pot. They will show a curvature or bend opposite to the bend of the stem. This curvature is in the direction of the pull of gravity. It is positive geotropism.
Chemotropism:Certain chemical substances are responsible to bring about curvature movements in plant organs. For instance, movement of Pollen tube towards ovary due to absorption of calcium and borate from style of carpel; movement of tentacles in Drosera, closing of lid of Nepenthes due to nitrogenous food, and penetration of haustoria of parasite into host body etc.
Hydrotropism:The paratonic curvature movements of growth in relation to the stimulus of water are called hydrotropic movements. The tropic response to the stimulus of water is called hydrotropism. The roots show positive hydrotropic response, i.e., they bend towards the water ). Hydrotropism is stronger in roots compared to geotropism.
