Question

Why auxinhormone increases the rate of growth in a stem but it decreases the rate of growth in a root?

Answer 1

Auxin hormone increases the rate of growth in shoot whereas its effect is opposite in roots. This is because the side of the root which is away from the light will have all the auxin concentrated in that part. Hence, the side of the root which is away from the light will grow slower; thereby, bending the root away from the light.