The movements in curvature of whole organ towards or away form the stimuli such as light, gravity and touch are called tropic movement. It has different types. It may be phototropism, geotropism and hydrotropism.

(a) Phototropism: The trupic movement of the part of plant in response to stimulus of light is called phototropism. It is caused due to differential growth of part of plant like root, stem or root.

(b)    Thigmotropism: The tropic movement in response to stimulus of touch is called thigmotropism. For example, climbing vines. When they come in contact with some solid object the growth on the opposite side of the contact increases. So tendril coils around the support.

(c)Chemotropism: The tropic movement in reiponse to some chemical is called chemotropism. The hyphae of the fungi are chemotropic.

(d)    Hydrotropism: The tropic movement of plant in response to stimulus of water is called hydrotropism. The growth of root toward water is due to positive hydrotropism. The shoot grow away from water is negative hydrotropic.



(e)Geotropism: The tropic movements in response to gravity are called geotropism. Root show positive geotropism, while shoot show negative geotropism.

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