Answer: The correct answer for the blank is-
A negative tropism is when a plant grows away from a stimulus.
Step-by-step explanation:
Tropism is a biological process that indicates growth or turning movement of an organism, generally a plant, as a response to a particular environmental stimulus (any change in the environment that causes the organism to respond).
A negative tropism means the growth of organsim is taking place away from the stimuli.
Example- Growth of shoot of plant away from the gravity depicts negative geotropism.