NEET BIOLOGY

Detailed explanation-1: -The plants have a chemical called auxin, which reacts in response to light. This causes the cells of the plants to elongate. Growth towards light is positive phototropism, while that away from the light is negative phototropism. The stem grows towards the direction of light and is called positively phototropic.

Detailed explanation-2: -Tropism is specific to the direction of the stimulus. Plants can either display a negative or positive movement in response to a stimulus. It is positive tropism when the movement is towards the direction of stimuli while it is negative tropism when the movement is away from the stimuli.

Detailed explanation-3: -Tropic movement in plants is the directional response to the presence of external stimuli. Such movements usually occur in the presence of external factors like – light, temperature, gravity, water, etc. 2.

Detailed explanation-4: -Tropic movements are important for plants because of the following reasons: They serve as protective function. They help in developing a sudden response for a stimulus or change. It helps in the growth of pollen tubes towards the ovules.

Detailed explanation-5: -Final Answer: The directional movement of plants in response to contact is thigmotropism.