Terminal Respiration of Vegetative Cells and Zygospores in Chlamydomonas reinhardi

Abstract

The respiration rate and the sensitivity of respiration to treatment with carbon monoxide and cyanide were examined in vegetative cells and germinating zygospores of C. reinhardi Dang. The respiration of the zygospores was cyanide sensitive (10-5 [image]) and was inhibited by carbon monoxide with the inhibition reversed by blue light, whereas the respiration of the vegetative cells was resistant to both cyanide (10-3 [image]) and carbon monoxide (99%). The transition from the sensitive to the resistant condition occurred between the 8th and 12th hour of germination, at the same time that the chlorophyll levels rose, or that photosynthesis began in the light. The terminal oxidase of the zygospores appeared to have a higher affinity for oxygen than that present in the vegetative cells. These observations are consistent with the hypothesis that a typical, inhibitor-sensitive respiratory pathway, mediated by cytochrome oxidase, is present in the zygospore stage of C. reinhardi, and that the increase in respiration and onset of photosynthesis, which take place during zygospore germination, are accompanied by a change to an inhibitor-resistant pathway which is present in the vegetative cells.