Explain the difference in function of auxins in plant shoots and roots.

Auxins are plant growth hormones found in both the roots and shoots of plants, in the shoots they promote growth whereas in the roots they inhibit it. In the shoots they cause cell elongation in the side of the cell in which they are present. For example, when the shoot is exposed to light the auxins accumulate on the side found in the shade. This increase in auxins causes more cell growth on the side in the shade, pushing the shoot upwards towards the light- an example of positive phototropism (growth towards light). Whereas in the root, auxins inhibit cell growth. For example, if a root is growing sideways, more auxins will accumulate on the lower side and as auxins inhibit growth in the root, there will be more cell growth on the upper side (where less auxins are present) of the root causing the root to bend downwards. This is an example of positive gravitropism (growth towards gravity).