Q31 of 231 Page 93

Why is the folding up of the leaves of a sensitive plant on touching with a finger not a tropism?

When we touch the leaves of a sensitive plant (like Mimosa pudica), they get folded. It is not a case of tropism because there is no dependency of direction of leaves movement on the direction of stimulus (touch).


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29

Name the plant hormones which are responsible for the following effects:

(a) falling of leaves


(b) opening of stomata


(c) bending of stem towards light


(d) closing of stomata

 30

Name the plant organs which are:

(a) positively phototropic


(b) positively geotropic


(c) negatively geotropic


(d) positively hydrotropic

 32

Why is the closing of a dandelion flower at dusk (when it gets dark) not a tropism?

 33

What is meant by ‘tropisms’ (or tropic movements)? Explain with an example.