ABA induces closure of stomata. Water stress in the roots can lead to a 40-fold increase in the ABA levels in the plant. An ABA-deficient tomato mutant, flacca, is unable to close stomata during drought stress5961.
http://www.iisc.ernet.in/currsci/may10/articles17.htm
ABA is also produced by some plant pathogenic fungi via a biosynthetic route different from ABA biosynthesis in plants. Abscisic acid owes its names to its role in the abscission of plant leaves. In preparation for winter, ABA is produced in terminal buds.
https://en.wikipedia.org/wiki/Abscisic_acid
ABSCISIC ACID. Abscisic acid (ABA) is often referred to as a inhibitory rather than stimulatory hormone. It is involved in the closure of stomata, bud and seed dormancy and is known to inhibit other hormonal actions. Abscisic acid (ABA) is often referred to as a inhibitory rather than stimulatory hormone. It is involved in the closure of stomata, bud and seed dormancy and is known to inhibit other hormonal actions. Discovery: F.T. Addicott and his associates discovered abscisic acid in the early 1960s in the process of studying abscission in cotton (commercially important for mechanization of cotton picking') .
http://www2.mcdaniel.edu/Biology/botf99/hormweb/haba.htm
1 Closure of Stomata -- Large amounts of abscisic acid in the leaves causes the stomata to close which helps the plant conserve water during droughts. 2  Reactions can be instigated within minutes of spraying... 3  commercially it is used in fields when droughts threaten.
http://www2.mcdaniel.edu/Biology/botf99/hormweb/haba.htm
The phytohormone abscisic acid (ABA) plays a regulatory role in many physiological processes in plants. Different stress conditions such as water, drought, cold, light, and temperature result in increased amounts of ABA.
http://www.iisc.ernet.in/currsci/may10/articles17.htm
ABA was originally believed to be involved in abscission. This is now known to be the case only in a small number of plants. ABA-mediated signaling also plays an important part in plant responses to environmental stress and plant pathogens.
https://en.wikipedia.org/wiki/Abscisic_acid
Abscisic acid has been found to function in the closing of these stomata during times when the plant does not require as much carbon dioxide or during drought times when the plant cannot afford to lose much water through transpiration. One of the crucial functions of abscisic acid is to inhibit seed germination. Abscisic acid has been found to stop a seed from germinating immediately once it has been placed in the soil. It actually causes the seed to enter a period of dormancy.
http://study.com/academy/lesson/abscisic-acid-in-plants-definition-function-quiz.html
Abscisic acid is also produced in the roots in response to decreased soil water potential and other situations in which the plant may be under stress. ABA then translocates to the leaves, where it rapidly alters the osmotic potential of stomatal guard cells, causing them to shrink and stomata to close.
https://en.wikipedia.org/wiki/Abscisic_acid
Abscisic acid (ABA), also known as abscisin II and dormin, is a plant hormone. ABA functions in many plant developmental processes, including bud dormancy. It is degraded by the enzyme (+)-abscisic acid 8'-hydroxylase into phaseic acid.
https://en.wikipedia.org/wiki/Abscisic_acid
Stress may induce common responses such as enhancement of plant hormones. For instance, wounding can induce the production of increased ethylene, auxin, and abscisic acid (ABA). Since many kinds of stresses including water, salt, and cold temperatures, induce ABA synthesis, ABA may be considered a plant stress hormone. It regulates several important aspects of plant growth and development.
http://www.iisc.ernet.in/currsci/may10/articles17.htm
function of abscisic acid,
The plant developmental processes, including bud dormancy is the function of abscisic acid. The function of abscisic acid is to develop plant, including bud dormancy.