Physiological role of nitrate under anaerobic stress in Saccharum officinarum callus cells tolerant and sensitive to anoxia

The physiological role of nitrate as a protective factor against anaerobic stress was studied in experiments with tolerant to anoxia sugarcane (Saccharum officibarum L.) callus lines obtained by in vitro selection in the absence of exogenous carbohydrates. Original cell lines, which were not subjected to selection and therefore more sensitive to oxygen shortage, served as a control. In these lines, anaerobic stress was created in the presence or absence of nitrate in nutrient medium. The presence of nitrate in nutrient medium increased markedly tolerance to anaerobic stress of both lines differing in their sensitivity to anaerobiosis. However, the degree of tolerance differed substantially in compared lines. In the presence of exogenous nitrate, in tolerant cells there were no signs of mitochondrial membrane destruction or degradation even after 72 h of anoxia, whereas in control cells 48-h anaerobic incubation led to the complete degradation of mitochondrial membranes and membranes of other organelles. It is concluded that significant increase in the tolerance of S. officinarum cells in the process of in vitro selection most likely occurred due to induction and stimulation of not only the processes of glycolysis and fermentation, but also nitrate and maybe nitrite utilization.