P and Q are two types of plants having weak stems which cannot stand upright on their own. The plants P and Q have organs R and S respectively which can grow towards any support which they happen to touch and wind around that support. It is- observed that organ R originates from the leaves of the plant whereas organ S originates directly from the stem of the plant.
(a) What is (i) R, and (ii) S?
(b) What is the name of growth movement exhibited by the organs R and S?
(c) Name the stimulus involved in this case.
(d) State whether the behaviour of organs R and S is a tropic movement or a nastic movement.
(e) Name one plant like P and another plant like Q.
(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).