Auxins are a group of hormones that are only present in plants. They are
mostly present in the tips of the stems and roots. The auxins help certain
grow more and faster.
The Auxins present in the stems help it grow faster, the auxins present in the
roots causes a decrease in growth rate.
If a plant was growing the side that is not facing the sun will have more auxin
and therefore grow more causing it to bend towards the sun. This is
highlighted in the picture.
In roots the Auxins causes less growth upwards and causes it to bend down
in the direction of gravity therefore the roots can get further into the ground.