Ethylene and cyanide induce a sharp increase in respiration in potato tubers (Solanum tuberosum, var. Russet) attended by changes in the glycolytic intermediates which indicate that both gases enhance glycolysis. The level of sucrose also increases in response to both treatments. The data are taken to indicate that both cyanide and ethylene either activate or affect the link between the conventional electron transport chain and the cyanide-insensitive path. It is further proposed that this activation may well be the primary event leading to the rise in respiration. Ethylene increases the level of adenosine 5'-triphosphate and it is suggested that because of the 4-to 6-fold increase in the rate of electron flux through site I, which continues to operate in the over-all cyanide-insensitive path, the absolute levels of adenosine 5'-triphosphate will also be expected to increase in the presence of cyanide. The increase in sucrose content is considered to be the consequence of the rise in adenosine 5'-triphosphate concentration.Ethylene and cyanide have been shown to elicit similar physiological changes in avocado fruits (23). At the time it was indicated that ethylene and cyanide, in stimulating respiration, may release the same regulatory restraints (although not necessarily by identical means). The effect of ethylene on plant respiration was described as a fundamental process independent of ripening. We have extended our studies of the effects of cyanide and ethylene to the respiration of potato tubers, an organ wherein respiration is stimulated both by ethylene and cyanide (15,16,20), and where ripening is not involved. MATERIAILS AND METHODSPotato tubers (Solanum tuberosum, var. Russet) were grown at Tule Lake, in northern California, and stored at 7 C. Before an experiment, tubers were put in 4-liter respiratory jars through which a stream of air or appropriate mixture of air and experimental gas was passed over the tubers at 50 ml/min. The rates of CO2 output and 02 uptake were determined with a 'This work was supported by a grant from the United States Public Health Service.Beckman infrared CO2 analyzer and oxygen analyzer, respectively.Phosphate esters and lactate were extracted and purified as described earlier (23), omitting charcoal purification in the case of ATP determination. They were determined enzymatically in systems linked to spectrophotometric measurements of changes in NADH levels (9). In the determination of simple sugars, the tissue was first homogenized in 10% cold perchloric acid and centrifuged, and the residue was twice extracted with 5% perchlorate and centrifuged. The three supernatants were combined, and the pH was adjusted to 7 with KOH. The extract was subsequently left overnight at 3 C. Potassium perchlorate was removed by centrifugation, and the supernatant solution was evaporated to about 5 ml with a rotary evaporator at 35 C. The extract was taken up to a convenient volume with distilled H20. Sugars were determined enzymatically according to previously published methods (...

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Integrated studies comprising biochemical and electron microscopic analysis suggested that the increase in respiratory activity of pea cotyledon mitochondria during germination results from further development of the original mitochondria present in dormant seeds. Electron microscopy of isolated mitochondria as well as mitochondria in situ has revealed that membranes are scarce in the mitochondria present in dormant seeds. Mitochondrial cristae become well developed during the initial stages of germination. Crude mitochondrial preparations from pea cotyledons were fractionated by sucrose density gradient centrifugation and analyzed through electron microscopy. These studies showed that, at all stages of germination, "peroxisome"-like structures were present in the fractions of higher sucrose densities than that containing mitochondria. Biochemical studies revealed that the activities of catalase (H2O2:H2O2 oxidoreductase, EC 1.11.1.6) and peroxidase (guaicol:H2O2 oxidoreductase, EC 1.11.1.7) were associated mainly with these fractions and their activities increased during germination.

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