Question

(a) How is movement of leaves of touch-me-not plant and the movement of growth in stem towards light differ?
(b) Give a suitable example of chemotropism?

Answer 1

(a) Movement of the leaves of touch-me-not plant are due to thigmonasty brought about by pressure changes. Nastic movements are non-directional.

While movement of the stem is a tropic movement (phototropic movement). Tropic movement is directional and happens in the direction of the external stimulus like the light in this case.

(b) Chemotropism is the movement or growth of an organism in response to chemical stimulus.

Example: Growth of pollen tube down the style during fertilization in response to the presence of sugars in the style.