Abstract :
: A greenhouse experiment was conducted on alfalfa (genotype Baghdadi) seedlings using 3 types of salts including NaCl (0, 100 mmol), KCl (0, 40 mmol) and CaCl2 (0, 20 mmol) to investigate the concentration of different solutes and salt tolerance. Na+, K+, Ca2+, Mg2+, Cl-, NO3- and SO42- concentrations and dry weight were separately determined in shoot and root. Chlorophyll (Chl) a and b, total chlorophyll, carotenoids, Malondialdehyde (MDA), Total Soluble Proteins (TSP) concentrations and activity of Peroxidase (POX) and Ascorbate Peroxidase (APX) were assessed in shoot. NaCl caused to decrease the K+, Ca2+ and Mg2+ concentrations in shoot and root. Na+ caused to suppress the Ca2+ absorption. Applying KCl and CaCl2 caused to increase the Cl- concentration in shoot and root. Results showed that there was not salt exclusion mechanism in studied genotype under salinity. Adding NaCl to nutrient solution led to decrease the TSP and MDA content while increasing the activity of both APX and POX. Activity of POX and APX was increased under KCl and CaCl2 treatments. Carotenoids concentrations were decreased under NaCl stress while increased under CaCl2 treatment. Negative effect of NaCl on concentration of Chl a was more than Chl b. Results of current experiment shows that KCl and CaCl2 caused to raise the antioxidative defense system under presence of NaCl. Studied seedlings were not able to prevent the salt accumulation in shoot and transferred high Na+ content from root to shoot while there was no reduction in dry weight under NaCl stress so it is probably that seedlings used salt inclusion to tolerate the water deficit generated by NaCl stress also could to eliminate the ions toxicity.
