Nodule functioning in trifoliate and pentafoliate mungbean genotypes as influenced by salinity

Abstract

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 (ψ(s)) and relative water content (RWC) of nodules decreased significantly, and proline content increased with increasing the salinity. The ψ(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.