A chemical substance P is made and secreted by the meristematic tissue at the tip of the 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 sunlight side of a stem or in shade.
(c) What is the effect of substance P on the rate of growth of (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.
A chemical substance P is made and secreted by the meristematic tissue at the tip of the 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 sunlight side of a stem or in shade.
(c) What is the effect of substance P on the rate of growth of (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.
(a) The chemical substance P is auxin.
(b) Auxin remains on the shaded side of the stem.
(c) Auxin increases the growth rate of shoots and decreases the growth rate of roots.
(d) Process Q is positive phototropism, whereas R is negative phototropism.
(e) The general name of chemical substances like auxin (P) is phytohormone. Cytokinins, gibberellins and abscisic acid are other examples of phytohormones.
(a) The chemical substance P is auxin.
(b) Auxin remains on the shaded side of the stem.
(c) Auxin increases the growth rate of shoots and decreases the growth rate of roots.
(d) Process Q is positive phototropism, whereas R is negative phototropism.
(e) The general name of chemical substances like auxin (P) is phytohormone. Cytokinins, gibberellins and abscisic acid are other examples of phytohormones.
