Inhibition of oxygen release by anoxia in a C3-plant (Nicotiana tabacum cv. Wisconsin 38). Comparison with C4-plants.

Tobacco leaves (Nicotiana tabacum var. Wisconsin 38) submitted to anaerobic conditions behave in a manner similar to that of maize, sugarcane, or sorghum leaves (C4-plants); more precisely, a lag time in O2 release is exhibited when the leaves are exposed to light after treatment in the dark under pure nitrogen. Although the conditions for the appearance of this phenomenon in tobacco are somewhat different, the main features are identical to those observed with maize: abolition of the lag time upon immediate exposure to light, release of CO2 under light (illumination burst of CO2), photochemical nature of the reactions involved in the abolition of the lag time, activation of oxygen release by far-red light, and the antagonistic effect of red and far-red light on the lag time. The high CO2 compensation point of tobacco leaves permits the classification of this plant among the C3 group. A comparison of these experimental results with others from the literature suggests than the distinguishing features between C3- and C4-plants are not as sharp as generally thought.