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A field experiment was conducted in a combinatorial approach to evaluate the performance of five aquatic plants, singly and in all possible combinations of two plants, for As removal from 4 L of 2500 μg L −1 As in 30 days. Under As stress, Hydrilla showed an increase in growth rate (19%) in comparison to control, while other plants demonstrated a decline. Among different combinations, Ceratophyllum + Lemna , Hydrilla + Ceratophyllum and Hydrilla + Wolffia showed higher growth in As (92%, 43%, and 33%, respectively) than under control conditions. Total As removal (μg) in 30 days was found to be the maximum for Ceratophyllum + Lemna (4365) followed by Hydrilla + Ceratophyllum (3326) and Hydrilla + Wolffia (1896). In all combinations of plants, Hydrilla always contributed more than 50%. The study advocates the use of Hydrilla / Ceratophyllum as one plant of choice to be used in combination. It also proposes to screen for different combinations of two of more plants for better application of phytoremediation technology in field. [ABSTRACT FROM AUTHOR]

The present study analyzed the effects of individual microbes and their consortium (Priestia endophytica NDAS01F , Bacillus licheniformis NDSA24R, and P. flexa NDAS28R) either alone or in interaction with thiourea (TU) on growth and responses of rice plants subjected to As stress (50 mg kg−1 in soil) in a pot experiment. The bacteria used in the experiment were isolated from As contaminated fields of Nadia, West Bengal and showed significant As removal potential in in vitro experiment. The results revealed significant growth improvement, biomass accumulation, and decline in malondialdehyde levels in rice plants in bacterial and TU treatments as compared to control As treatment. The best results were observed in a bacterial consortium (B1-2-3), which induced a profound increase of 65%, 43%, 127% and 83% in root length, shoot length, leaf width and fresh weight, respectively. Sulfur metabolism and cell wall synthesis were stimulated upon bacterial and TU amendment in plants. The maximum reduction in As concentration was observed in B2 in roots (−55%) and in B1-2-3 in shoot (−83%). The combined treatment of B1-2-3 + TU proved to be less effective as compared to that of B1-2-3 in terms of As reduction and growth improvement. Hence, the usage of bacterial consortium obtained in the present work is a sustainable approach, which might find relevance in field conditions to achieve As reduction in rice grains and to attain higher growth of plants without the need for additional TU supplementation. [Display omitted] • Bacteria isolated from Nadia, West Bengal were used for consortium. • Bacterial consortium promoted growth of plants and reduced arsenic concentration. • Arsenic translocation from root to shoot was significantly decreased. • Bacterial consortium + thiourea did not result in synergistic effects on growth. • Bacterial consortium + thiourea did not cause additional arsenic reduction. [ABSTRACT FROM AUTHOR]

The exposure of paddy fields to arsenic (As) through groundwater irrigation is a serious concern that may not only lead to As accumulation to unacceptable levels but also interfere with mineral nutrients in rice grains. In the present field study, profiling of the mineral nutrients (iron (Fe), phosphorous, zinc, and selenium (Se)) was done in various rice genotypes with respect to As accumulation. A significant genotypic variation was observed in elemental retention on root Fe plaque and their accumulation in various plant parts including grains, specific As uptake (29–167 mg kg dw), as well as As transfer factor (4–45%). Grains retained the least level of As (0.7–3%) with inorganic As species being the dominant forms, while organic As species, viz., dimethylarsinic acid and monomethylarsonic acid, were non-detectable. In all tested varieties, the level of Se was low (0.05–0.12 mg kg dw), whereas that of As was high (0.4–1.68 mg kg dw), considering their safe/recommended daily intake limits, which may not warrant their human consumption. Hence, their utilization may increase the risk of arsenicosis, when grown in As-contaminated areas. [ABSTRACT FROM AUTHOR]

The physiological, biochemical, and proteomic changes in germinating rice seedlings were investigated under arsenic stress. A marked decrease in germination percentage, shoot, and root elongation as well as plant biomass was observed with arsenic treatments, as compared to control, whereas accumulation of arsenic and malondialdehyde (MDA) in seedlings were increased significantly with increasing arsenic concentration (both AsIII and AsV). The up-regulation of some antioxidant enzyme activities and the isozymes of superoxide dismutase (SOD, EC 1.15.1.1), ascorbate peroxidase (APX, EC 1.11.1.11), peroxidase (POD, EC 1.11.1.7), and glutathione reductase (GR, 1.6.4.2) substantiated that arsenic accumulation generated oxidative stress, which was more pronounced in As(III) treatment. We also studied the protective effect of reduced glutathione (GSH) and cysteine (Cys) to As(III)/As(V) stressed seedlings. Both GSH and Cys imparted enhanced tolerance to seedlings against arsenic stress. Seedlings growth improved while level of MDA declined significantly when GSH and Cys were supplemented to As(III)/As(V) treatments suggesting GSH and Cys-mediated protection against oxidative stress. The arsenic content was highest in roots of seedlings grown in As(III) in the presence of GSH/Cys. However, in case of As(V) plus GSH or Cys, the arsenic content in seedlings was highest in shoots. The results are suggestive of differential metabolism of As(III) and As(V) in rice. [Copyright &y& Elsevier]

In the present study, arsenic (As) toxicity amelioration potential of a consortium of plant growth promoting rhizobacterium ( Pseudomonas putida ) and alga ( Chlorella vulgaris ) was evaluated during arsenate (AsV) exposure to rice ( Oryza sativa ) plants for 15 d. The consortium mediated amelioration of As toxicity was evident through improved growth of rice plants (root and shoot length and biomass) and reduced oxidative stress [as level of superoxide radicals (O 2 − ), hydrogen peroxide (H 2 O 2 ) and membrane damage]. The positive responses were attributable to a significant decline in As accumulation in root (94 mg kg −1 dw) and shoot (51 mg kg −1 dw) in consortium ( P. putida  +  C. vulgaris ) inoculated seedlings as compared to As alone exposed plants (156 and 98 mg kg −1 dw, respectively). There were also significant changes in the level of various nutrient elements (Mn, Fe, Co, Zn, Mo and Cu), thiols and in the activities of antioxidant and thiol metabolism enzymes in the consortium inoculated seedlings that allowed the plants to tolerate As stress effectively and achieve better growth. The study demonstrated that consortium of P. putida and C. vulgaris may alleviate As stress and improve growth of rice seedlings along with reduction in As levels. [ABSTRACT FROM AUTHOR]