for any and every phase of growth, differentiation and development of plants, one or the other PGR has some
Growth hormones are the hormones released by plants to regulate their growth. There exists 5 types of growth hormone in plants i.e. auxin, cytokinin, gibberellins,ethylene, and abscisic acid. According to the function of these hormones in respect to each other, they can be classified as:
1) Complimentary hormones:
Complimentary hormones are the hormones which work together to enhance the growth of the plant. For example: ethylene and abscisic acid work together to promote endosperm rupture during seed germination.
2) Antagonistic hormones:
Antagonistic hormone are the hormones which work opposite to each other, opposing each others action on the growth of the plant. For example: auxin and cytokinin are antogonistic as auxin promote apical dominance while cytokinin promote the formation of lateral buds.
3) Individualistic hormones:
Individualistic hormone are the hormones which perform there own individual function irrespective of any other hormone. For example Gibberellins are individualistic hormone which promote the formation of parthenogenic (seedless) fruits.
4) Synergistic effects:
Synergism can be defined as the interaction where two hormones work together and the overall effect is greater than the sum of their individual effects. For example auxin and cytokinin work synergistically to promote plant growth. At different ratios they promote growth of different parts of plants.