Effects of chloride and sulphate types of salinization and desalinization on nodulation and nitrogen fixation in chickpea

Chickpea was grown in sand culture under nonsaline conditions and chloride and sulphate types of salinization. Chloride salinity reduced the weight of the nodules, leghaemoglobin concentration, N_2- fixing efficiency and root and shoot weights more than sulphate, whereas the production of nodules was reduced more with sulphate than chloride. However, shifting of well nodulated plants to saline conditions led to an increased production of nodules (more with chloride) but to a loss in nodule fresh weight (more with sulphate). Senescence of the existing nodules was further evident, within 10 days of shifting, from a decrease in leghaemoglobin concentration and reduced efficiency to fix nitrogen, chloride being more inhibitory than sulphate. However, upon desalinization after 40 days of sowing, the development of leghaemoglobin and N_2- fixing efficiency in the nodules was faster in chloride than sulphate. Growth of the root and shoot also followed an identical pattern but nodule growth was of the same magnitude in the two cases. Further, the production of new nodules was faster with sulphate than chloride which was just the reverse to what it was before desalinization. The present studies thus show that the effects and after-effects of salinity on the processes of nodule production, their growth and N_2- fixation vary with the type of salinity and the time of salinization.