Nodule Functioning in Trifoliate and Pentafoliate Mungbean Genotypes as Influenced by Salinity

Two genotypes of mungbean differing in the leaf shape, K-851 (trifoliate) and a mutant (pentafoliate), were exposed to salinity (0, 2.5, 5, 10 dS m^–1) for 3, 6 and 9 d at flowering stage (40 – 45 d after sowing) to see the effect of salinity on nodule functioning. In both the genotypes, osmotic potential (_s) and relative water content (RWC) of nodules decreased significantly, and proline content increased with increasing the salinity. The _s of nodules was more decreased in the mutant than in genotype K-851, while reverse was true for RWC and proline accumulation. A remarkable increase in ethylene evolution was noticed from nodulated roots with the increasing level and duration of salinity and was much higher in K-851. A sharp decline in leghemoglobin content and acetylene reduction assay (ARA) of the nodules was observed with the salinity and this decrease was more marked in K-851 than the mutant. N content declined while Na⁺/K⁺ ratio and Cl^– content increased significantly. The mutant maintained better N status but lower Na⁺/K⁺ ratio and Cl^– content in nodules than K-851. Nodule dry matter also declined with salinity and the decrease was more expressed in K-851. Thus the functioning of nodules in the mutant was better than in the genotype K-851 under stress conditions.