Endosperms from castor beans (Ricinus communis) germinated for 0 to 6 days were exposed to anoxia for 0 to 15 hours. Ethanol, the only alcohol detected by gas chromatography in the tissue, accumulates to a concentration of 15 millimolar during the first 2 to 4 hours of anoxia and subsequently decreases. The absolute amount of ethanol varies from 10 micromoles per 5-day endosperm after 4 hours anoxia to less than 1 micromole in 2-day endosperm after 4 hours. Lactate content is 2 micromoles or less per endosperm. Alcohol dehydrogenase and pyruvate decarboxylase activities, which are localized in cytosolic fractions, are not greatly affected by anoxia. The recoveries of the marker enzymes and protein in endoplasmic reticulum (ER) and mitochondrial fractions decrease during anoxia. After 15 hours, the recovery of NADPH cytochrome c reductase is 15% of that in controls, fumarase is 50%, and catalase is 75%.Glyoxysomes and ER are capable ofconverting ethanol to acetaidehyde which was measured using the fluorogenic reagent, 5,5-dimethyl-1,3-cyclohexanedione. The glyoxysomal activity is dependent on a hydrogen peroxide-generating substrate and the ER is dependent on NADPH. However, these activities are less than 3% of the alcohol dehydrogenase activity.Hypoxic stress and alcoholic fermentation are common features of plant metabolism. Ethanol is produced by flooded seedlings (1, 18, 19), ice encased leaves (2), root nodules (20), and tissues exposed to S02 and 03 (10). The endosperm of germinating castor bean endosperm is an appropriate model to study anaerobic stress and alcohol metabolism. This tissue responds to anoxia by generating ethanol and smaller amounts of lactate (11). ER, mitochondria, and glyoxysomes, subcellular components which depend on 02 have been isolated and well characterized (3, 6, 21). The glyoxylate cycle has been shown to participate in ethanol metabolism (17). In the earlier investigation of anoxic castor bean endosperm, Kobr and Beevers (1 1) followed ethanol accumulation for 2 h in endosperms after 5 d germination. However, plant tissues are often capable of producing ethanol for longer periods of time (1,4).One purpose of this study was to determine the extent and regulation ofethanol production in castor bean during prolonged anoxia as a function of seedling age. Also, we examined the possibility that other alcohols might be produced and metabolized during anoxia. Because the endosperm initially contains very little carbohydrate (7), it was expected that little or no ethanol would be generated prior to the establishment of gluconeogenesis. We explored the possibility that the capacity for ethanol generation might be regulated by pyruvate decarboxylase and alcohol dehydrogenase, the enzymes responsible for the final steps of ethanol production.The second major aim of this study was to examine the subcellular locations of ethanol metabolism and the effects of anoxia on 02 requiring organelles. It has been reported that rat liver microsomal Cyt P450 and peroxisomal catalase are capable ...