Abscisic acid levels in the grain of wild rice.

In a study to determine if ABA could be responsible for wild rice grain dormancy, non-dormant wild rice grains (stored in water at 3 deg C for 330 days) were dehulled, scarified and placed in sol. of 0-20 mg ABA/l for 7 days. Germination decreased as ABA conc. increased. No germination was obtained at or above 5 mg ABA/l. Washing the ABA-treated grains with water did not reverse the inhibition. Free ABA/grain decreased from 12.29 to 4.27 ng and conjugated ABA from 7.14 to 4.86 ng during 146 days of storage in water at 3 deg C. The ABA contents of hulls, pericarps, embryos, and endosperms were determined in dormant and non-dormant (120 days after storage) grains. Total ABA/g dry wt. of embryo and pericarp tissue exceeded that of hulls and endosperms by a factor of 50 in both dormant and non-dormant grain. Total ABA/g dry wt. of embryos, pericarps and hulls was significantly less in non-dormant grain.