Anaerobic Respiration in the Dormancy of Rice Seed

Abstract

We investigated the effects of high temperature treatment (40°C three weeks) on dormant rice seeds of Hadsaduri (Oryza sativa cv.) which was known as a variety of deep dormancy and results obtained are summarized as follows; 1. The seed of which dormancy was broken by high temperature treatment could germinate under both aerobic and anaerobic conditions, whereas dormant seed could not germinate under the anaerobic condition. 2. Warburg manometric techniques were used for the determination of respiratory gas exchange. In the case of non-dormant seeds, the amount of released carbon dioxide always exceeded that of oxygen uptake. Whereas the dormant seeds showed nearly the same amount of oxygen uptake and carbon dioxide release. 3. Determination of ethyl alcohol was carried out by gas chromatography. Non-dormant seeds usually produced more amount of ethyl alcohol than dormant seeds. When both dormant and non-dormant seeds were incubated under nitrogen gas at 30°C, the same tendency as above was observed. 4. When non-dormant seeds were co-treated with sodium iodoacetate, which was known as one of the inhibitors of enzyme SH group, at 5mM and 10mM concentrations, the production of ethyl alcohol was inhibited. Germination of hulled rice of non-dormant seeds was not affected up to the concentraton to 10mM under aerobic condition, but almost completely inhibited at 5mM under submerged condition. From the facts described above, it might be possible to consider that the dormant rice seed had the aerobic respiratory pathway but had not an active anaerobic respiratory pathway sufficient for germination. Effects of high temperature treatment on breaking the dormancy of rice seed may be attributed to the activation of anaerobic respiration.