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 (ABA or abscisin II) 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.

Abscisic acid
Stereo, skeletal formula of abscisic acid
Names
Preferred 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
Identifiers
3D model (JSmol)
3DMet
Abbreviations ABA
2698956
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.040.275 Edit this at Wikidata
EC Number
  • 244-319-5
MeSH Abscisic+Acid
RTECS number
  • RZ2475100
UNII
  • InChI=1S/C15H20O4/c1-10(7-13(17)18)5-6-15(19)11(2)8-12(16)9-14(15,3)4/h5-8,19H,9H2,1-4H3,(H,17,18)/b6-5+,10-7-/t15-/m1/s1 checkY
    Key: JLIDBLDQVAYHNE-YKALOCIXSA-N checkY
  • OC(=O)\C=C(\C)/C=C/[C@@]1(O)C(C)=CC(=O)CC1(C)C
Properties
C15H20O4
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
Hazards
GHS labelling:
GHS07: Exclamation mark
Warning
H315, H319, H335
P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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