The question is incomplete as it does not have the options which are:
A. More; more; gravitropism
B. More; less; phototropism
C. Less; more; gravitropism
D. Less; less; phototropism
Answer:
B. More; less; phototropism
Step-by-step explanation:
Auxin is a hormone which is involved in the plant growth and the development by increasing the flexibility of the cell wall of the plant.
In the given question, the vertical root is rotated to the horizontal orientation which will be sensed by the roots and the roots will then redistribute the auxin in the roots.
The auxin will be transported to the lower areas but the growth of the root in the lower portion will be lowered as a result of which root will grow downward. This is considered a condition called positive gravitropism or negative phototropism.
Since the distribution of auxin is dependent on the presence or absence of light therefore this phenomenon will be referred to as the phototropism.
Thus, Option-B is correct.