<b>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.</b><b>(a) </b>What is the chemical substance P ?<b>(b) </b>State whether P prefers to remains in the sunlit side of a stem or in shade.<b>(c)</b> What is the effect of substance P on the rate of growth (i) a root, and (ii) a stem ?<b>(d)</b> What is the name of process (i) Q, and (ii) R ?<b>(e)</b> What is the general name of chemical substances like P ? Name another substance which belongs to this class of chemical substances.