The chemical substance P is made and secreted by the meristematic tissue at the tip of stem (or shoot) of a plant. The chemical substance P is responsible for a phenomenon Q in plants in which the stem bends towards a source of light. The same chemical substance P has an opposite effect on the root of a plant. It causes the root of a plant to bend away from the source of light in a process called R.(a) What is the chemical substance P ?(b) State whether P prefers to remains in the sunlit side of a stem or in shade.(c) What is the effect of substance P on the rate of growth (i) a root, and (ii) a stem ?(d) What is the name of process (i) Q, and (ii) R ?(e) What is the general name of chemical substances like P ? Name another substance which belongs to this class of chemical substances.

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