Spring.wmf (18300 bytes) Plant Physiology (Biology 327)  - Dr. Stephen G. Saupe;  College of St. Benedict/ St. John's University;  Biology Department; Collegeville, MN  56321; (320) 363 - 2782; (320) 363 - 3202, fax;    ssaupe@csbsju.edu

Abscisic Acid (ABA)

I. General

II. Chemistry

III. Biosynthesis

IV. Bioassays/Analysis

A. Bioassays � there are several including:

B. Analysis � Gas chromatography, HPLC, and immunoassay

V. Disposal/Regulation 

VI. Transport - xylem and phloem (greater amounts)

VII. Actions

A. Growth Inhibitor
    Widespread growth inhibitor; often antagonistic of GA actions

B. Maintains or "seals in" bud and seed dormancy (i.e., prevents germination)
    In fact, ABA is made during the terminal stages of embryo development. Among it's roles in seed dormancy is to: (1) provide desiccation tolerance of the embryo by promoting synthesis of proteins involved in the process; and (b) promote accumulation of seed storage proteins.

C. Prevents vivipary
    Development of the embryo without a dormant period. Some evidence: viviparous mutants have reduced [ABA]; and fluridone stimulates treatment stimulates vivipary (fluridone is an inhibitor of carotenoid biosynthesis that blocks ABA production)

D. Inhibits auxin induced growth (seems to block the H+ pump)

E. Stomatal closure under water stress (remember our unit on gas exchange?)

F. Abscission & senescence
    Involved, though perhaps only a minor role

VIII. Mechanism of action

A. Effects on plasma membrane

B. Inhibits protein synthesis

C. Regulation of genes (transcription)

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Last updated:  01/07/2009     � Copyright  by SG Saupe