Question

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.

(c) Name the stimulus involved in this case.

Answer 1

• The stimulus involved is touch or contact with other objects which helps climbers to grow.
  
• The directional growth movement of a plant part in response to the touch of an object is called thigmotropism.