Effects of saline-sodic stress on organic acid in sweet sorghum

In order to understand the effects of saline-sodic( based on the composition of Na2CO3 and Na HCO3) stress on the organic acid contents in sweet sorghum plant( Sorghum dochna( Forssk.)),the changes of organic acid contents and phosphoenolpyruvate carboxylase( PEPC)activities in above-and under-ground parts of sorghum varieties 314 B and M-81 E were studied.The results showed that eight different acids( i.e.,oxalic acid,tartaric acid,formic acid,pyruvic acid,malic acid,lactic acid,acetic acid,and citric acid) were detected from both of the above-and under-ground parts,while succinic acid was only found in the roots under saline-sodic stress. Meanwhile,the levels of most organic acids decreased with the increment of stress level,whereas few of them increased slightly. The PEPC activity increased at low saline-sodic concentration,but decreased at high saline-sodic concentration. There was no correlation between organic acid level and PEPC activity. Nevertheless,when the PEPC activity increased,the decreasing rate of organic acids changed slightly and vice versa. In terms of the levels of organic acid and PEPC activity,M-81E( stronger tolerance) suffered a weaker damage than 314B( lower tolerance) under saline-sodic stress.