The Effect of Hypoxia on Recovery from Sublethal Damage in Chlamydomonas

SummaryExperiments with Chlamydomonas reinhardii showed that the sparing effect of fractionation was unaffected by the absence of oxygen during irradiation, provided that oxygen was present during the fractionation interval. When oxygen was excluded from the system during the interval between doses, recovery was reduced or absent. If air was admitted to the irradiated system after a two-hour period of hypoxia, cells recovered promptly. The extent of the sparing effect was dependent on the concentration of oxygen present during the fractionation interval. The concentrations of oxygen which reduced recovery were in the range which reduced the rate of respiration of the cells. These results suggest that the recovery process in Chlamydomonas requires energy which is supplied in the cell by aerobic respiration.