Question

What are plant hormones ? name the plant hormones responsible for the following
A. Growth of stem
B. Promotion cell division
C. Inhibits of growth
D. Elongation of cells.

Answer 1

Hint: Plants need sunlight, water, oxygen, minerals for their growth and development. Growth and development in plants are collectively regulated by the listed external as well as some intrinsic factors.

Complete answer:
The chemicals which regulate plant growth are called plant hormones. Plant hormones are chemical compounds which are present in very low concentration in the plants. In plants, mainly five hormones are present.
> Auxins ( which are derivatives of indole)
> Gibberellins ( which are derivatives of terpenes)
> Cytokinins ( which are derivatives of adenine)
> Abscisic acids or ABA (which are derivatives of carotenoids)
> Ethylene ( which are derivatives of gases)
All these hormones are produced in almost all parts of the plant and are even transmitted to various parts of the plant. Roles of all hormones can be complementary or antagonistic. Hormones play an important role in many processes like vernalization, phototropism, seed germination, dormancy, etc. along with extrinsic factors. Plant hormones control the growth and development activities like cell division, enlargement, flowering, seed formation, dormancy, and abscission.
Plant hormones are categorized into two categories
> Plant growth promoters
> Plant growth inhibitors
Growth of stem: Agricultural and horticultural practices consume a significant amount of auxins due to its replicative property. Auxin is found in growing apices of roots and stems and then migrate to other parts to show their function
Promotion cell division: Cytokinins play an important role in the cytokinesis process. when rapid cell division occurs cytokinins are naturally synthesized in the plants.
Inhibits of growth: Abscisic is a growth-inhibiting hormone. Plant metabolism is inhibited and abscission and dormancy are regulated. It is also called a stress hormone.
Elongation of cells: Ethylene acts as a growth promoter as well as an inhibitor. Occurs in gaseous form. It hastens the ripening of fruits.

Note:
Plant hormones are also called phytohormones. Other than 5 hormones there are other hormones too that affect the plant’s physiological process, for example, brassinosteroids, salicylates, jasmonates, etc.