Plant Hormone Abscisic acid (ABA): Major Functions

Stress hormone

• Chemically: dextro rotatory cis-sesquiterpene
• Active form of ABA (+) cis ABA & (+)-2-trans ABA

Abscisic acid (ABA) which regulates flowering in Arabidopsis

                 Synthesis/precursor

•  Mevalonic acid or xanthophylls like violaxanthin

                                                                            Major effects

           Stress response: water stress increases ABA production that initially induce stomatal closure and later increases water holding capacity of root tissues and promotes root growth and inhibits shoot growth.

• Maintains seed dormancy 
• Promotes abscission and senescence
• Incorrectly named, not related to abscission, ethylene is the hormone that is directly involved in abscission. ABA promotes abscission.

• Important in water stress and other stresses 
• Causes stomatal closure
•  Prevents premature germination of seeds
• Changes gene expression patterns