Studies on the Breaking of Dormancy in Barnyardgrass Seed : II. Change of the dormancy-breaking effect of several inhibitors against oxidation-reduction system by dormancy stage

Abstract

This paper forms the second part of a series of investigations on the control of the breaking of dormancy in barnyardgrass (Echinochloa Crusgalli Beauv. var. oryzicola Ohwi) seed. This investigation evaluated the change of the dormancy-breaking effect of several inhibitors against oxidation-reduction system through the process of the breaking of dormancy. 1) In deep dormancy stage, 8-oxyquinoline, KCN, DIECA, HgCl₂, Na₂S and salicylaldoxime-all showed a stimulative effect on the breaking of dormancy in considerable degree. But thiourea, NaN₃ and BAL had no effect. 2) In deep dormancy stage, the inhibition of oxygen uptake by salicyladoxime, DIECA or HgCl₂ was no more than 30 percent under the treatment inducing the dormancy-breaking effect. In addition, thiourea did not inhibit the oxygen uptake under the same treatment. 3) In shallow dormancy stage, the dormancy-breaking effect of KCN and HgCl₂ increased remarkably. However, 8-oxyquinoline, DIECA and salicylaldoxime showed less effect than KCN and HgCl₂. 4) The effect of 8-oxyquinoline in shallow stage was inferior to the level in deep stage by all means of treated period or concentration. 5) On the contrary, NaN₃ had a noted effect only in shallow stage. These results indicate that the endogenous mechanism of dormancy in barnyardgrass is changing gradually, corresponding with the environmental conditions.