What Is Abscisic Acid?

What is abscisic acid; defined as a plant hormone that allows the plant to adjust to the outside stress it may encounter.

Abscisic acid is defined as a plant hormone that mainly acts to inhibit growth, promotes dormancy, and to help the plant tolerate stressful conditions.

Abscisic acid is named so because it was believed that this hormone caused the abscission of leaves from deciduous trees in the fall. The plants growth slows down and then it will assume a dormant state. This is the complete opposite of what auxin, gibberellins, and cytokinins, the other plant hormones will due to the plant. Inside the terminal bud the hormone abscisic acid is produced. The slow growth and direction of leaf primordial develops scales to protect the dormant buds during the cold season.

This hormone inhibits the division of the cell in the vascular cambium. Also preparing for the winter by suspending primary and secondary growth. The most impressive affect of abscisic acid in the inhibition of growth and the maintenance done on the dormancy of buds. Yet this is not enough to keep the dormancy of buds up for the long term.

Auxin, cytokinins, and gibberellins do the opposite of abscisic acid, they stimulate growth in the tissues. Acting as a growth inhibitor abscisic acid also suspends growth at the onset of dormancy. Germination will begin when there is an increase of activity of gibberellins or abscisic acid is removed or by its inactivation. Heavy rain can cause the abscisic acid to be washed out. Light and other stimulates can trigger the degradation of abscisic acid. The ratio between abscisic acid and gibberellins determine if the dormancy of the terminal buds is controlled by a balance of hormones by the absolute concentration of abscisic acid in dormant seeds when it is an inhibitor of germination. The germination levels are controlled by the equilibrium of auxin(s), gibberellin(s), and cytokinins(s) and one and abscisic acid on the other. The exact role of the abscisic acid is unknown when the abscission acid appears not to have much effect on the abscission of leaves while there is defiantly an effect on fruit abscission.

Also this hormone acts a "stress" hormone, helping plants cope with adverse conditions that the plant might come across. An example of this is when a flower begins to wilt the abscisic acid collects in the leaves which in turn causes the stomata to close. Once the stomata is closing the transportation is reduced and prevents further water loss.

Abscisic acid is a substance that causes bud dormancy therefore it is also known as a dormin. There is a related compound call xanthoxine is an intermediate of the abscisic acid biosynthesis or if it is an independent product.

Overall abscisic acid is a hormone that can slow down and cause parts of the plants metabolism for a certain amount of time. Abscisic acid can be easily removed form the tissue, but this effect is reversible. Even if the seeds are in the humid surrounding, the inhibition of seed germination does not occur. Yet when it is isolated and transferred to a normal immediately they will start to germinate.

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