Define thigmotropism, phototropism, and gravitropism and give an example of each

a) Thigmotropism

b) Phototropism

c) Gravitropism

Explanation:

A) the turning or bending of a plant or other organism in response to a touch stimulus. example:  the folding movement of the Mimosa pudica leaflets, can be considered as an example of thigmonastism.

B) the orientation of a plant or other organism in response to light, either towards the source of light ( positive phototropism ) or away from it ( negative phototropism ).example: Sunflower is a highly phototropic plant. They grow towards the sun and are also seen tracking the movement of the sun throughout the day. That is, the flower keeps changing its direction with the movement of the sun. Sunflower requires more light for its growth and survival.

C) The gravity-directed growth process, called gravitropism, dictates upward shoot growth to ensure a proper positioning of the leaves for efficient photosynthesis and gas exchange. example: tree has fallen over and due to gravitropism exhibits this arched growth.  

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