In negative geotropism of shoots, auxin is redistributed to the side of the cell, where the amyloplasts have accumulated, where it cell elongation.

a. Lower

b. Stimulates

In negative geotropism of shoots, auxin is redistributed to the lower side of the cell, where the amyloplasts have accumulated, where it stimulates cell elongation.

Explanation:

Geotropism can be defined as the direction the various parts of a plant grows toward due to the stimulus which in this case is the force of gravity. Geotropism in plants can be negative or positive.

Negative geotropism occurs when the shoots of a plant grows upwards against the force of gravity.

oxygen +1 most likely