Final answer:
A tropism is an organism’s growth response either toward (positive tropism) or away from (negative tropism) an environmental stimulus, such as light, gravity, or touch.
Step-by-step explanation:
A tropism is the turning of all or part of an organism in a particular direction in response to an environmental stimulus. Plants exhibit various kinds of tropisms, including phototropism (growth toward light), gravitropism (growth in response to gravity), and thigmotropism (response to touch).
Auxins, which are plant hormones, play a vital role by migrating to one side of the plant and inducing faster growth on that side, causing the plant to bend towards the stimulus.
A response toward a stimulus is known as a positive tropism, whereas a response away from it is a negative tropism.