[Effect of phosphorus deficiency on alternative respiratory pathway and its relation with O2-* accumulation in suspension-cultured tobacco cells].

Effects of phosphorus deficiency on alternative respiratory pathway and its relation with O2- production were investigated in two lines of suspension-cultured tobacco cells which have different tolerances to P deficiency. Oxford cells were shown to be much more tolerant than K326 (Fig. 1). There were no apparent differences in inorganic and total phosphorous content between the two cell lines (Fig.2). The capacity and activity of alternative respiratory pathway were decreased by P deficiency in K326 cells but were little influenced in Oxford cells. Under either P-deficient or sufficient condition, the capacity and activity of alternative respiratory pathway were always higher in Oxford than in K326. When mitochondria were isolated and used for the same study, similar results were obtained as described above (Fig.3 and Fig.4). The expression of AOX at protein level was induced by P deficiency in both lines to similar extents (Fig.5). O2- content in K326 cells was significantly higher under P deficiency but little affected in Oxford (Fig.6). It is suggested that alternative respiratory pathway may be associated with tolerance of tobacco cells to P deficiency and may play a role in scavenging reactive oxygen species.