Question

Explain the following terms:

(i) Tropism

(ii) Positive tropism

(iii) Negative tropism

(iv) Nastic movement​

Answer 1

Answer:

(a) The growth of a plant part in response to a stimulus is called positive tropism and if the growth of a plant part is away from the stimulus, then it is called negative tropism.Example: The roots of a plant go towards earth in response to gravity is an example of positive geotropism whereas stem grows away from earth against gravity is an example of negative geotropism.  (b) The directional growth movement of a plant part in response to the touch of an object is called thigmotropism.Example: Tendrils grow towards any support which they happen to touch and wind around it.  (c) Tendrils grow towards a stimulus hence it is a directional movement which shows that it is a case of thigmotropism whereas, the folding of leaves in mimosa plant does not depend on the direction of stimulus (touch) which shows that .

Explanation:

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Answer 2

Answer:

i) tropism- A tropism is a biological phenomenon, indicating growth or turning movement of a biological organism.

ii) positive tropism- The growth of a plant part in response to a stimulus is called positive tropism.

iii) negative tropism - if the growth of a plant part is away from the stimulus, then it is called negative tropism.

iv) nastic movement -Nastic movement are directional responses to stimuli, and are usually associated with plants.