plant hormone that stimulates stomatal closure and promotes seed and bud dormancy. Inhibits shoot growth but may promote root growth. Plays a role in wounding responses and in abscission ~ of leaves and fruit.

Merriam-Webster Online Dictionary
abscisic acid (noun)
a plant hormone CHO that is a sesquiterpene widespread in nature and that typically promotes leaf abscission and dormancy and has an inhibitory effect on cell elongation - 15 20 4
abscisic acid (Wikipedia)
Abscisic acid
Stereo, skeletal formula of abscisic acid
Systematic IUPAC name
(2Z,4E)-5-[(1S)-1-hydroxy-2,6,6-trimethyl-4-oxocyclohex-2-en-1-yl]-3-methylpenta-2,4-dienoic acid
Other names
(2Z,4E)-(S)-5-(1-Hydroxy-2,6,6-trimethyl-4-oxo-2-cyclohexen-1-yl)-3-methyl-2,4-pentanedienoic acid; Dormic acid;[citation needed] Dormin
3D model (JSmol)
3DMet B00898
Abbreviations ABA
ECHA InfoCard 100.040.275
EC Number 244-319-5
MeSH Abscisic+Acid
RTECS number RZ2475100
Molar mass 264.321 g·mol−1
Appearance Colorless crystals
Density 1.193 g/mL
Melting point 163 °C (325 °F; 436 K)
log P 1.896
Acidity (pKa) 4.868
Basicity (pKb) 9.129
S-phrases (outdated) S22, S24/25
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Abscisic acid (ABA) is a plant hormone. ABA functions in many plant developmental processes, including seed and bud dormancy, the control of organ size and stomatal closure. It is especially important for plants in the response to environmental stresses, including drought, soil salinity, cold tolerance, freezing tolerance, heat stress and heavy metal ion tolerance.

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