Roles of Abscisic Acid

Abscisic acid (ABA) is a particularly interesting hormone with regard to the regulation of its own levels. Its levels rise and fall dramatically in several kinds of tissues in response to environmental and developmental changes. Following are the roles of Abscisic acid:

• When leaves of mesophytic plants are water stressed (i.e. under water shortage condition) ABA levels can rise from.10 to 50-fold within 4-8 hours. When the plants are re-watered, the ABA levels drop dramatically within 4-8 hours.
• It is generally believed that Abscisic acid induces dormancy in seeds to tide over adverse environmental conditions such as freezing temperature or stresses of hot dry periods causing water shortage. Dormancy is induced also in deciduous plants.
• You have already learnt that when Abscisic acid accumulates in guard cells during periods of water shortage, it causes stomates to close thus enabling the plants to recover water balance.
• The name Abscisic acid was originally proposed as early investigators believed that it caused flowers, fruits and leaves to abscise (fall). However, now there is dispute over whether ABA is involved at all in the abscission process.