Rhizobium induced modulation of growth and photosynthetic efficiency of Lens culinaris Medik. grown on fly ash amended soil by antioxidants regulation

Rhizobium leguminosarum is a rhizospheres’ nitrogen fixing microbe that improves plant growth and productivity by releasing sufficient nutrient sources from the root, by biological nitrogen fixation, solubilization of phosphorous, acquisition of iron, and enhancement of antioxidant activity in plants. On this account, a greenhouse experiment was carried out to assess the feasibility of growing lentil (Lens culinaris Medik.) on fly ash (FA) amended soil (0%, 10%, 20%, and 30%) in combination with R. leguminosarum inoculation. The data was recorded at 45 day after sowing to evaluate the plant growth characteristics, photosynthetic variables (total chlorophyll and carotenoid pigments, carbonic anhydrase activity, nitrate reductase activity), damage markers (ROS, MDA, and cell viability), and defensive factors (proline and antioxidants). Among the FA-proportions tested, 20% proved most favorable in all the mentioned attributes while 30% concentration had negative repercussions on all the variables. Rhizobium inoculation had synergistic effect on all the concentrations being maximum on 20% FA. Thus, Rhizobium and 20% FA caused a significant increase on growth characteristics, photosynthetic pigments; stomatal behavior (aperture shape, size, and frequency of stomata); and activity of CA and NR, and cell viability. Application of Rhizobium on 20% FA was corroborated with decline in MDA and ROS contents and a coordinated enhancement of the activity of SOD, CAT, and POX. Therefore, 20% FA with fly ash-tolerant strain of Rhizobium in Lens culinaris may be utilized as an integrated approach towards sustainable agriculture and an impulse of management of fly-ash.