Seed dormancy and germination of Echinochloa oryzicola Vasing. Substantive evidences for alcohol fermentation at early germination.

Abstract

Seed germination of Echinochloa oryzicola, a gramineous weed in flooded rice, was studied to obtain substantive evidence for the operation of alcohol fermentation by comparing the patterns of change in alcohol dehydrogenase and cytochrome c oxidase activities with those in shoot and root growth, and by determining the quantitative relationship between CO2 and ethanol production. Non-dormant seeds incubated in air at 30°C, in the light had initially high activity of alcohol dehydrogenase, but it rapidly decreased and the activity of cytochrome c oxidase started to increase when the radicle growth began. However, the seeds in nitrogen, which showed good growth of the coleoptile with no radicle protrusion, maintained high activity of the dehydrogenase and low activity of the oxidase. Non-dormant seeds both in air and nitrogen produced ethanol and CO2 at constant rates, and molar ratios of the production, ethanol/CO2, until radicle protrusion were nearly 0.8 in air and 1.0 in nitrogen. These results indicated that the seeds respired mainly through alcohol fermentation regardless of O2 tension of the surrounding atmosphere. Moreover, the seeds grew shoots even under the anaerobic condition, but with no radicle growth, as often observed at water flooded rice fields.