P and Q are two t

(a) (i) R is a leaf tendril.

(ii) S is a stem tendril.

(b) A tendril is a specialized leaf, petiole or stem with a threadlike shape. It is used by climbing plants for support and attachment. The tendrils grow towards the things they happen to touch and the phenomenon is known as thigmotropism.

(c) Touch (support) is the stimulus involved in this case.

(d) behaviour of organs R and S is a tropic movement. Tropic movement is always in the direction of stimulus. All parts of a plant (roots, stem and leaves etc.) exhibit tropic movements.

(e) Pea plant is like P (leaf tendrils) and bitter gourd plant is like Q (stem tendrils).