These are chemical compounds present in plants in low concentrations but they perform important functions such as growth and development, regulation of organ size, protection against pathogens, and stress tolerance.
There are mainly 5 plant hormones namely Auxin, Gibberellins, Cytokinin, Abscisic acid, and Ethylene
Gibberellins which break the dormancy in seeds and buds
Cytokinin promotes cell division.
Abscisic acid promotes the closing of stomata.
Ethylene is responsible for senescence and aging of the plant along with fruit ripening.
Auxin:
It is the first plant hormone that is a derivative of indole, Indole-3-acetic acid (IAA) which promotes cell enlargement and cell differentiation.
Auxins are also called plant growth regulators.
Auxins are present in shoot and root tips.
Auxins help in cell division, stem and root growth in root initiation, and bud and flower growth.