Plant hormones (also called phytohormones) are natural, chemical substances produced in small amounts that regulate plant growth, development, and responses to the environment. 1. Auxins 2.Gibberellins (GA) 3. Cytokinins 4. Abscisic Acid (ABA) 5. Ethylene Summary Table Hormone Major Action Growth Effects Auxins Cell elongation Tropisms, root initiation, apical dominance Gibberellins Stem elongation, germination Bolting, […]