Boron (B) is an essential micronutrient, crucial for the growth and development of crop plants. However, the essential to a toxic range of B in the plant is exceptionally narrow, and symptoms develop with a slight change in its concentration in soil. The morphological and anatomical response, such as leaf chlorosis, stunted growth, and impairment in the xylem and phloem development occurs under B-toxicity. The transport of B in the plant occurs via transpiration stream with the involvement of B-channels and transporter in the roots. The higher accumulation of B in source and sink tissue tends to have lower photosynthetic, chlorophyll content, infertility, failure of pollen tube formation and germination, impairment of cell wall formation, and disruption of membrane systems. Excess B in the plant hinders the uptake of other micronutrients, hormone transport, and metabolite partitioning. B-mediated reactive oxygen species production leads to the synthesis of antioxidant enzymes which help to scavenge these molecules and prevent the plant from further oxidative damage. This review highlights morpho-anatomical, physiological, biochemical, and molecular responses of the plant under B toxicity and thereby might help the researchers to understand the related mechanism and design strategies to develop B tolerant cultivars. Graphical Abstract The physio-biochemical and molecular responses and mechanism of B uptake under its toxic condition have been illustrated. The spatial distribution of boron under its toxic condition and its accumulation in the plant might be regulated with sugar alcohols (polyols). This review throws light on the elevated level of B in the soil-plant system and provides management strategies for alleviating B toxicity in the plant.

Rice (Oryza sativa L.) grain yield is reduced by drought stress during reproductive stages. In this work, the effects of foliar selenium (Se) spray on the reduction of drought stress are measured and the most critical stage of rice is identified. Three field experiments were carried out. In experiments I and II, the sensitive stage was determined by imposing drought stress at the panicle initiation and flowering stages by withholding irrigation for 10, 15, 20, and 25 days. In experiment III, drought stress was induced by depriving plants of moisture for 20 or 25 days. Se spray was then applied at rates of 0, 10, and 20 mg L⁻¹ to alleviate the drought, and its effects were evaluated. Overall, it was reported that the panicle initiation stage was more vulnerable to drought stress than the flowering stage, as evidenced by a larger reduction in grain yield. Employing Se as a foliar spray at a rate of 20 mg L⁻¹ under drought stress enhanced the number of filled grains m⁻², the total number of grains m⁻², and grain yield ha⁻¹ by 22.0, 4.3, and 11.0%, respectively, over water spray. This shows a positive interaction or synergistic interaction between drought tolerance and selenium application. These results demonstrate that foliage supplementation of Se at a dosage of 20 mg L⁻¹ alleviate the adverse effects of drought stress at the panicle initiation stage in rice cultivation. Se mitigated the negative effects of drought by improving the membrane stability index, relative water content, and proline content.

Groundwater arsenic (As) pollution is a naturally occurring phenomenon posing serious threats to human health. To mitigate this issue, we synthesized a novel bentonite-based engineered nano zero-valent iron (nZVI-Bento) material to remove As from contaminated soil and water. Sorption isotherm and kinetics models were employed to understand the mechanisms governing As removal. Experimental and model predicted values of adsorption capacity (q_e or q_t) were compared to evaluate the adequacy of the models, substantiated by error function analysis, and the best-fit model was selected based on corrected Akaike Information Criterion (AICc). The non-linear regression fitting of both adsorption isotherm and kinetic models revealed lower values of error and lower AICc values than the linear regression models. The pseudo-second-order (non-linear) fit was the best fit among kinetic models with the lowest AICc values, at 57.5 (nZVI-Bare) and 71.9 (nZVI-Bento), while the Freundlich equation was the best fit among the isotherm models, showing the lowest AICc values, at 105.5 (nZVI-Bare) and 105.1 (nZVI-Bento). The adsorption maxima (q_max) predicted by the non-linear Langmuir adsorption isotherm were 354.3 and 198.5 mg g⁻¹ for nZVI-Bare and nZVI-Bento, respectively. The nZVI-Bento successfully reduced As in water (initial As concentration = 5 mg L⁻¹; adsorbent dose = 0.5 g L⁻¹) to below permissible limits for drinking water (10 µg L⁻¹). The nZVI-Bento @ 1% (w/w) could stabilize As in soils by increasing the amorphous Fe bound fraction and significantly diminish the non-specific and specifically bound fraction of As in soil. Considering the enhanced stability of the novel nZVI-Bento (upto 60 days) as compared to the unmodified product, it is envisaged that the synthesized product could be effectively used for removing As from water to make it safe for human consumption.