Ali has some pea plants in his garden which need a support to grow as seen in the picture given below.
Define the above phenomenon.
Topic: Definition of thigmotropism
Answer
THIGMOTROPISM is the directional growth movement of a plant part in response to the stimulus of TOUCH or contact with a solid object.
A definition of any tropism must contain three elements: it is a GROWTH movement, it is DIRECTIONAL (towards or away from the stimulus), and it names the STIMULUS.
HOW IT WORKS, if the question allows an extra line: where the tendril touches the support, the cells on the side AWAY from the contact grow faster than those touching it. That unequal growth curves the tendril around the support.
DO NOT CONFUSE tropic with NASTIC movements. A nastic movement is also a response to a stimulus but is NOT directional — the drooping of Mimosa leaves when touched is the same direction whichever side is touched, and it is a movement of turgor rather than of growth.