Plant growth regulators (also called plant hormones) are numerous chemical substances that profoundly influence the growth and differentiation of plant cells, tissues, and organs. Plant growth regulators function as chemical messengers for intercellular communication. They work together coordinating the growth and development of cells. There are currently five recognized groups of plant hormones which are as follows.
Auxins: They stimulate cell elongation. It also controls xylem differentiation and helps in cell division.
Gibberellins: The main effect of gibberellins in plants is to cause stem elongation and flowering. They are also prominently involved in mobilization of endosperm reserves during early embryo growth and seed germination.
Cytokinins: They are able to stimulate cell division and induce shoot bud formation in tissue culture. They usually act as antagonists to auxins.
Ethylene: It is a simple gaseous hydrocarbon with the chemical structure CH
. It is apparently not required for normal vegetative growth. However, it can have a significant impact on the development of root and shoots.
Abscisic acid: It acts as a general plant growth and seed germination inhibitor and an inhibitor of plant metabolism.