The word hormone is derived from the Greek word "hormon", meaning "to excite". In plants, control and coordination are performed by chemical substances called plant hormones (phytohormones), which are transported to different parts of the plant. In vertebrate animals, the endocrine system acts through chemical messengers called hormones, produced by specialised glands. Digestion, metabolism, growth, development and reproduction are controlled by hormones.
1. Plant Hormones – An Overview
Plant hormones are organic molecules produced at extremely low concentration in plants. They control morphological, physiological and biochemical responses. In plants, several cells are capable of producing hormones.
There are five major classes of plant hormones:
| Growth Promoters | Growth Inhibitors |
|---|---|
| Auxins | Abscisic Acid (ABA) |
| Cytokinins | Ethylene |
| Gibberellins | – |