How many hormones are there in a plant and what are their functions
Hormones are chemical substances which acts like messenger molecules in the body.
Primarily there are five major hormones present in a plant.
d) Abscisic acid
Each hormone differs in its effects. The auxins, gibberellins, and cytokinins act as growth stimulators, whereas, abscisic acid and ethylene act as growth inhibitors.
Functions of Auxin:
a) Cell elongation of stems and roots
b) Helps in cell division and xylem differentiation
c) Development of fruit without fertilization
d) Prevents premature fall of leaves, flowers and fruits
e) Useful in stem cuttings and grafting where it initiates rooting
f) Promotes flowering.
Functions of Cytokinin
1) Cytokinins are capable of stimulating cell division along with auxins.
2) They promote cell elongation.
3) They have the ability to delay the process of ageing in leaves.
4) Cytokinins can prolong the life of fresh leaf crops like cabbage, and spinach.
5) They are also used for keeping the flowers fresh.
6) Cytokinins are most effective in breaking dormancy of buds and seeds.
7) The levels of cytokinins decrease in senescing leaves.
Functions of Gibberellin:
a) Seed Germination
b) Dormancy of Buds
c) Root Growth
d) Elongation of the Internodes
Functions of Abscisic acid
a) Stimulates the closing of stomata in the epidermis
b) Favorsin the development and maturation of seeds
c) Inhibits plant metabolism and seed germination
d) Mainlyinvolved in regulating abscission and dormancy
e) Used as a spraying agent on trees to regulate the dropping of fruits
f) Induces dormancy in seeds and helps in withstanding desiccation and other unfavorable growth factors.
Functions of ethylene
a) Stimulating fruit ripening.
b) Helps in determining the sex of a flower.
c) It is involved in the production of female flowers in a male plant.
d) Promotes Apo-geotropism in roots.
e) Induces seed germination.
f) Inhibits stem growth.