What are their physiological effects of Abscisic acid in plants and its role in agriculture ?

Explanation

Physiological affects:
(i) It helpis in reducing transpiration rate by closing stomata. It inhibits `K^(+)` uptake by guard cells and promotes the leakage of malic acid. It results in closure of stomata.
(ii) It spoils chlorphylls, proteins and nucleic acids of leaves making them yellow.
(iii) Inhibition of cell division and cell elongation.
(iv) ABA is a powerful growth inhibitor. It causes `50%` inhibition of growth in Oat coleoptile.
(v) It promotes the abscission of leaves, flowers and fruits by forming abscission layers.
(vii) ABA plays an improtant role in plants during water stress and drring drought conditions. It results in loss of turgor and closure of stomata.
(viii) It has anti-auxin and anti-gibberellin proporty.
(ix) Abscisic acid promotes senescence in leaves by causing loss of chlorophyll pigment decreasing the rate of photosynthesis and changing the rate of proteins and nucleic acid synthesis.
Agricultral Role:
(i) In Cannabis sativa, induces male flower formation on female plants.
(ii) Induction of flowers in short day plants.
(iii) It promotes sprouting in storage organs like Potato.
(iv) ABA plays an important role in plants during water stress drought conditions.
(v) It inhibits the shoot growth and promotes growth of root system. This character protect the plants from water stress. Hence, ABA is called as stress hormone.