What are plant hormones?

Plant hormones or phytohormones are signal molecules that occur in extremely low concentrations within the plants. Plant hormones control all aspects of plant growth and development, from stress tolerance to reproductive development. (i) Growth of the stem is regulated by Gibberellins. (ii) Promotion of cell division is regulated by Cytokinins. (iii) Inhibition of growth is regulated by Abscisic acid. (iv) Elongation of cells is regulated by Auxins.