Seed dormancy and germination of Echinochloa oryzicola VASING. An observation through respiration and several enzyme activities.

Abstract

As the flrst part of a series of experiments to elucidate the ecophysiological mechanisms of seed dormancy and germination of Echinochloa oryzicola VASING., and observation was made through respiration and several enzyme activities during imbibition at 30°C in the light. Those determined were the pattern of changes of the dormant and non-dormant seeds in CO2/O2 exchange, ethanol production and activities of G6PDH, 6PGDH, ADH, ICDH, cytochrome c oxidase, polyphenol oxidase, catalase and peroxidase. In the dormant seeds, there were virtually no changes observed throughout the imbibition period, and the seeds appeared to respire to a small extent through the conventional electron transport chain since the RQ values were maintained at nearly 1.0. However, in the non-dormant seeds both RQ values and ADH activity increased sharply until protrusion of the coleoptile and/or coleorhiza, and after this period cytochrome c oxidase activity started to increase throughout germination and the RQ values approached 1.0. It was, therefore, suggested that the non-dormant seeds respire through alcohol fermentation during the early imbibitional period, and then through the conventional electron transport chain after the breakage of the outer barriers. The sharply increased activity of ADH observed at an early stage of imbibition could be a key metabolic character prior to the visible sign of germination: protrusion of the coleoptile and/or coleorhiza.