Abstract
The course of respiration in control leaves of tobacco (Nicotiana tabacum L.) that were illuminated 4 to 5 hours and then darkened 0.25 to 10 hours and in tobacco leaves starved of carbohydrate by 14 hours or more of darkness was measured as CO(2) efflux in light and darkness into CO(2)-free atmospheres containing 0.04, 2.23, 21, 40, and 100% O(2).Control and starved leaves showed a postillumination burst of CO(2) that differed from the usual rapid postillumination burst of control leaves in its onset and duration and its sensitivity to O(2) and starvation. Relative to control leaves, starved leaves lacked the initial postillumination burst of photorespiration and the O(2)-stimulated CO(2) efflux in the light, but these characteristics were regained when starved leaves were permitted to assimilate CO(2) from air or N(2) for as little as 20 minutes. Five respiratory patterns of CO(2) evolution, two in the light and three in darkness, were identified by manipulating light, darkness, starvation, and O(2) concentration.The CO(2) compensation concentrations varied with O(2) but were alike in control and starved leaves regardless of the presence or absence of photorespiratory characteristics and rates of respiration in light and darkness.