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Abscisic Acid Levels in the Grain of Wild Rice¹

Prolonged grain dormancy hinders wild rice (Zizania palustris L.) domestication. The purpose of this research was to determine if the inhibitor, abscisic acid (ABA), may be responsible tor wild rice grain dormancy.

Nondormant wild rice grains (stored in water at 3 C for 330 days) were dehulled, scarified, and placed in ABA solutions ranging in concentration from 0 to 20 mg/liter for 7 days. Germination decreased as ABA concentrations increased. No germination was obtained at or above 5 mg/liter of ABA. Washing the ABA-treated grains with water did not reverse the inhibition.

Free and conjugated ABA were determined chromatographically in dehulled grains during a storage period of 146 days in water at 3 C. Free ABA per grain decreased from 12.29 ng to 4.27 ng, and conjugated ABA from 7.14 to 4.86 ng during 146 days of storage.

The ABA contents of hulls, pericarps, embryos, and endosperms were determined in dormant and nondormant (120 days after storage) grains. Total ABA per gram dry weight of embryo and pericarp tissue exceeded that of hulls and endosperms by a factor of 50 in both dormant and nondormant grain. Total ABA per gram dry weight of embryos, pericarps, and hulls was significantly less in nondormant grain. The high concentration of ABA in dormant grain, especially hi the embryo and pericarp, may be one cause of dormancy in wild rice grain.

Key Words: Germination • Embryo • Pericarp • Endosperm • Hulls • ABA • Bound ABA • Dormancy • Zizania palustris L.

² Former graduate research assistant and professor, Dep. of Agronomy and Plant Genetics and associate professor, Dep. of Horticultural Science and Landscape Architecture, Univ. of Minnesota, St. Paul.

Received for publication November 13, 1978.