Morphological and physio-biochemical characterization of Brassica juncea L. Czern. & Coss. genotypes under salt stress

Soil salinity is one of the major factors responsible for the low productivity of crop plants and has become an increasing threat for agriculture. In this context, the selection of tolerant genotype/s may be one of the remedies. Keeping this in view, the effect of NaCl (0-120 mM) stress on shoot length (SL) plant(-1), area (A) leaf(-1), leaf area index (LAI), fresh weight (FW) and dry weight (DW) plant(-1), stomatal conductance (g(s)), net photosynthetic rate (P-N), total chlorophyll (Chl) content, malondialdehyde (MDA) content, sensitivity rate index (SRI), leaf-nitrogen (N), potassium (K) and sodium (Na) content, leaf-K/Na ratio, nitrate reductase (NR: EC. 1.6.6.1) and ATP-sulphurylase (ATP-S: EC.2.7.7.4) activities and proline (Pro) and glycinebetaine (GB) content of ten genotypes of Brassica juncea L. was studied at 55 and 65 days after sowing (DAS). NaCl treatments decreased all the above parameters, except Pro, GB, MDA, Na and SRI at both stages. Salt stress resulted in accumulation of Pro and GB, in all genotypes. The magnitude of increase in both osmolytes (Pro and GB) was higher in genotype G(8) than the other genotypes. Salt stress increased MDA and Na content while it decreased Chl, N and K content and K/Na ratio, Chl content, NR and ATP-S activities in all genotypes. But the magnitude of increase in MDA and Na content and decrease in SL plant(-1), A leaf(-1), LAI, P-N, g(s), Chl content and NR and ATP-S activities in genotype G(8) was more than that of other genotypes. These results suggest that the salt-tolerant genotype may have better osmotic adjustment and protection from free radicals by increasing the accumulation of Pro and GB content with overproduction of N and K and higher K/Na, NR and ATP-S activities under salinity stress.