Explain the physiological effects of ABA.

Explanation

ABA - Abscisic acid is a phytohormone.
Physiological effects
1. It helps in reducing transpiration rate by closing stomata. It inhibits `K^(+)` uptake by gurad cells and promotes the leakage of malic acid. It results in cloures of stomata.
2. It spoils chlorophylls, proteins and nucleic acids of leaves making them yellow.
3. Inhibition of cell division and cell elongation.
4. ABA is a powerful growth inhibtor. It causes 50% inhibition of growth in Oat coleptile.
6. It induces bud and seed dormancy.
6. It promotes the abscission of leaves, flowers and fruits by forming abscission layers.
7. ABA plays an important role in plants during water strees and during drought conditions. It result in loss of turgor and closure of stomata.
8. It has anti - auxin and anti - gibberellin property.
9. 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.