SummaryDormancy of six varieties of paddy, of three maturity groups, was studied under six seed-treatments. One type showed no dormancy but others showed dormancy in varying degrees 15 days after harvest. Dormancy was completely broken either by removing the kernels from the glumes, or by puncturing the glumes, or by putting acid-treated seeds in an atmosphere saturated with oxygen. The germination percentages were also significantly increased when seeds were treated with N/10 sulphuric acid solution for four hours, or when seeds were put in atmospheres saturated with oxygen. Speed of germination did not improve, as in the case of seeds germinated after four months of harvest, except in cases where the kernels were removed from the glumes or the glumes were punctured. The causes of dormancy of rice seeds were assumed to reside in the flowing glumes (lemma and palea), and different seed-treatments improved the germination of rice seeds by increasing the permeability of the glumes to oxygen and/or reducing the resistance of the tough glume covers over the germinating embryos. The magnitude of the treatment effects differed with variety. These studies suggest methods of improving germination.
