Salt induced inhibition in photosynthetic parameters and polyamine accumulation in two legume cultivars and its amelioration by pretreatment of seeds with NaCl

Enhancement of salt tolerance by pretreatment with sublethal dose of NaCl (50mM) has been investigated in arhar (Cajanas cajan L.) and maskalai (Vigna mungo L.) seedlings. Degradation of photosynthetic pigments in both the NaCl stressed legume cultivars resulted in less photosynthetic activity to occur. This was evident from reduced Hill activity recorded. NaCl stress hampered stomatal conductance that subsequently affected internal CO² concentration, net photosynthetic rate and also transpiration rate. Both the tested cultivars accumulated polyamines to limit cellular damage under such stressed conditions. Increased level of (Spermine+Spermidine)/Putrescine ratio and decreased level of cadavarine were observed in the nonpretreated seedlings grown under NaCl stress. However, seed pretreatment with 50mM NaCl for two hours helped the cultivars to overcome adverse effects caused by NaCl stress on stomatal activity, gas exchange parameters and polyamine contents that resulted the cultivars to acclimate such that it improved their metabolism under saline conditions.