(a) Seismonastic movement are the various type of responses and movements which are shown by plants on receiving stimulus. The stimulus may be electrical, chemical, pressure, touch, heat, etc. The plant shows some kind of change in their structure and move away from the source of stimulus.
(b) There are many different types of movements shown by the plants.
Phototropism is movements towards the light. The plant moves towards the source of sunlight.
Geotropism is the movement towards the soil. This is the movement shown by roots towards the ground in search of water and minerals.
Hydrotropism is the movement towards water. This is the movement shown by roots towards the source of water.
Chemostropism is the movement towards the chemicals. The male gametes moves towards the egg cell before fertilisation.
Seismonastic movements are the movements in which the plant moves away from the stimulus. The plant Mimosa pudica shows folding of the leaflets when touched.