Effects of salt stress on growth, nodulation and nitrogen fixation in cowpea and mung beans

The effects of salt stress on growth, nodulation, and nitrogen accumulation in cowpea (Vigna sinensis) and mung beans (Vigna aureus) were studied in sand culture. Salinity (NaCl) retarded the growth of leaves, stem and roots of both the crops. Root growth of mung beans was more sensitive to the increase in salt stress than that of cowpea. The relative growth rates of stressed plant parts declined initially but were subsequently higher than those of control for a period, suggesting that the plants tended to adapt to unfavourable environment even while being stressed. The total nodule number, weight and nitrogen content per plant decreased due to salt treatment, which interfered with the initiation of nodules but not with their further development. There was a considerable fall in the nitrogen fixation efficiency of mung beans under saline environment; it was not so in cowpea