Phytohormones

Chemical substances that stimulate & coordinate response in plants at low concentrations.

Phytohormones are transported by

The phloem

Types of phytohormones

Auxin, Gibberellin, Cytokinin, Abscisic acid & Ethylene

A hormone that stimulates the ripening of fruits:

Ethylene

A hormone that controlled the growth of shoot & root

Auxin

High auxin concentration in the root will cause

Inhibition of cells elongation in the root.

High auxin concentration in the shoot will cause

Increment of cells elongation in the shoot.

Role of auxin in phototropism

Auxin is higher on the shaded side, causes the cells on the shaded side to elongate more and causes the shoot to bend upward.

Role of auxin in geotropism

Auxin pool at the bottom part of the root inhibits cell elongation causes the root tips to bend downward.

Part of plants that are positive phototropism

The shoots