Effect of various salt-alkaline mixed stress conditions on sunflower seedlings and analysis of their stress factors

The buffer capacity of the treatment solution was taken as a stress factor in order to simplify the stress factor analysis. The results of the statistical analysis showed that for the stress factors of the salt-alkali mix stress, [CO32−] and [HCO3−] could be fully represented by the buffer capacity; [Na+] could be fully represented by salinity; whereas [SO42−] was negligible. Therefore, four factors, salinity, buffer capacity, pH and [Cl−], could reflect all of stress factors. Perfect linear correlations were observed between all strain indices and the four stress factors. However, the effects of the four stress factors on the strain indices were significantly different in magnitude. Buffer capacity and salinity were dominant factors for all strain indices. Thus, it is reasonable to consider the sum of salinity plus buffer capacity as the strength value of salt-alkali mix stress. Furthermore, the relationships between different strain indices and various stress factors were shown to be different.