Question

How does auxin produce gravitropism in a plant that is placed on its side?

a. Auxin accumulates on the lower surface of the root and inhibits elongation of cells in that region.
b. Auxin accumulates on the lower surface of the root and stimulates elongation of cells in that region.
c. Auxin accumulates on the side of the leaf opposite the sunlight and inhibits elongation of cells in that region.
d. Auxin accumulates on the side of the leaf opposite the sunlight and stimulates elongation of cells in that region.

Answer 1

Auxin accumulates on the lower side when a plant is placed on its side, and in roots, this inhibits elongation, causing positive gravitropism, while in shoots, it stimulates elongation, resulting in negative gravitropism.

Step-by-step explanation:

Auxin produces gravitropism in a plant placed on its side through the differential growth of cells. When a plant is positioned on its side, auxin accumulates on the lower side due to gravity. In the roots, auxin inhibits the elongation of the cells in the lower region, which in contrast, allows cells on the upper side to elongate normally. This differential growth causes the root to bend downward, displaying what is known as positive gravitropism. Conversely, in the shoots, auxin stimulates the elongation of cells on the lower side, promoting upward curvature known as negative gravitropism, enabling the shoots to grow upwards.