Q32 of 231 Page 93

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

The closing of a dandelion flower at dusk (when it gets dark) is not an example of a tropism because there is no dependency of the direction of movement of petals of dandelion flower on the direction of stimulus (light).


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30

Name the plant organs which are:

(a) positively phototropic


(b) positively geotropic


(c) negatively geotropic


(d) positively hydrotropic

 31

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

 33

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

 33

What are the different types of tropisms? Define each type of tropism. Write the name of stimulus in each case.