ABSTRACT
Plant growth regulators (PGRs)/phytohormones are organic compounds other than nutrients that modify plant biological processes. They are signal molecules and act as messengers. PGRs are useful because they can modify plant processes. Auxin is a generic term used to denote a group of compounds, characterized by their activity to induce cell division and cell elongation in shoot cells. A gibberellin may be defined as a compound that has a gibbane skeleton that stimulates cell division or cell elongation or both. Gibberellins are named after the fungus, Gibberella fujikuroi that caused rice plants to grow abnormally tall. Cytokinins are plant growth substances that cause cell division, but have no role in extension of growth. Polyamines are low cationic compounds implicated in an overwhelming array of plant growth and developmental processes. The growth inhibitors are a group of plant growth substances that inhibit / retard physiological or a biochemical processes in plants.
