S. N. Singh

Various combinations of fly ash tolerant bacteria isolated from the rhizospheric zone of Typha latifolia naturally growing on a fly ash dump site were tested for enhanced metal uptake by Brassica juncea grown in fly ash amended with press mud. After enrichment of the bacteria in a nutrient broth, they were subsequently applied to the rhizospheric zone of B. juncea in different combinations. When the metal analysis was done in the plants at their maturity, it was revealed that out of 11 bacterial consortia prepared from the different combinations of four bacterial strains, Micrococcus roseus NBRFT2 (MTCC 9018), Bacillus endophyticus NBRFT4 (MTCC 9021), Paenibacillus macerans NBRFT5 (MTCC 8912) and Bacillus pumilus NBRFT9 (MTCC 8913), a combination of NBRFT5, NBRFT4 and NBRFT9 (ST3) was found to have induced the highest metal accumulations as compared to other consortia. The bioaugmentation of the ST3 consortium enhanced Fe accumulation by 247%, Ni by 231% and Zn by 223% in B. juncea as compared to control plants. These values were found to be significantly higher than the other bacterial consortia. Bacteria were also found to produce siderophores which could enhance the metal uptake by plants through metal mobilization. Besides siderophores, bacteria are also known to produce protons, organic acids and enzymes which enhance the metal mobilization and boost the phytoextraction process. The translocation of metals from root to stem was invariably higher than from stem to leaf. Hence, ST3 was adjudged the best consortium to be used in the field application to accelerate the phytoextraction of metals from fly ash by B. juncea.

An experiment was conducted to assess the role of different concentrations of dicyandiamide (DCD), a potent nitrification inhibitor, on temporal changes in nitrous oxide emission from sandy loam agricultural soil. It was found that with increasing concentration of DCD i.e. from 6 to 12% of nitrogen applied in the form of urea, there was a decrease in the both average and peak N₂O emissions. However, from 14% DCD treated soil, there was a non-significant alteration in the N₂O emission. Maximum average N₂O efflux of 217.55 μg m⁻² h⁻¹ was noted from control plots. As compared to control, there was an attenuation of 50, 58, 65, and 91% average N₂O efflux from 6, 8, 10 and 12% DCD applied pots, respectively, whereas, there was a negative average of N₂O efflux from the soil with 14% DCD treatment. The soil N content also showed a significant correlation with N₂O emission. Therefore, 12% DCD treatment has been found to be the best with regard to attenuation of nitrous oxide from sandy loam agricultural soils.

Auto-pollution is the by-product of our mechanized mobility, which adversely affects both plant and human life. However, plants growing in the urban locations provide a great respite to us from the brunt of auto-pollution by absorbing the pollutants at their foliar surface. Foliar surface configuration and biochemical changes in two selected plant species, namely Ficus religiosa L. and Thevetia nerifolia L., growing at IT crossing (highly polluted sites), Picup bhawan crossing (moderately polluted site) and Kukrail Forest Picnic Spot (Low polluted site) were investigated. It was observed that auto-exhaust pollution showed marked alterations in photosynthetic pigments, protein and cysteine contents and also in leaf area and foliar surface architecture of plants growing at HP site as compared to LP site. The changes in the foliar configuration reveal that these plants can be used as biomarkers of auto-pollution.