Question

Under normal conditions, the roots of plants grow downward. This illustrates what type of tropism?

Answer 1

Tropism is the growth toward or away from a stimulus, and it happens to plants (it's different than movement). The tropism that's indicated can be of two types: phototropism, when the roots grows away from the stimulus of light, or gravitropism, when the roots are pushed downwards by gravity and grows towards it.