DENDROLOGY

Detailed explanation-1: -In the process of plant roots growing in the direction of gravity by gravitropism, high concentrations of auxin move towards the cells on the bottom side of the root. This suppresses growth on this side, while allowing cell elongation on the top of the root.

Detailed explanation-2: -Gravitropism ensures that roots grow into the soil and that shoots grow toward sunlight. Growth of the shoot apical tip upward is called negative gravitropism, whereas growth of the roots downward is called positive gravitropism.

Detailed explanation-3: -Roots display positive geotropism when they grow downward, while shoots display negative geotropism when they grow upward.