The Effects of Inorganic Ions on Dormancy in Rice Seed.

The germination of dormant rice seed is stimulated by nitrate, nitrite, and hydroxylamine, but only slightly or usually not at all by ammonium ions. Urea and a number of amino acids have no effect. Steeping the dormant seeds in solutions of low pH (2.0 or below) before the seeds are set to terminate in water stimulates germination. The pH of the steeping solution has no effect within the range pH 3.0 to 11.0. Steeping at pH 12.0 and above retards the breaking of dormancy. The pH of the medium in which the seeds are set to germinate has no effect on the percentage germination of a dormant population over the range 3.0 to 8.4 or a little above, but outside this range germination is inhibited. By the application of both nitrate and high concentrations of hydrogen ions in the steeping solution a number of dormant seeds are stimulated to germinate which otherwise would not have been affected by the nitrate or hydrogen ions alone. Cu₊₊, Hg₊₊, Ag₊₊, and, to a lesser extent, MoO_4^-- ions retard the breaking of dormancy at concentrations which do not affect the percentage germination of populations which have completely broken dormancy. None of the other metal ions which have been tried (Na⁺, K⁺, Mg⁺⁺, Mn⁺⁺, Fe⁺⁺, Fe⁺⁺⁺, Co⁺⁺, Ni⁺⁺, Zn⁺⁺) had any significant effect on percentage germination at concentrations up to 10^-2 M. [ABSTRACT FROM AUTHOR]