Environmental contamination with arsenic (As) is a global environmental, agricultural and health issue due to the highly toxic and carcinogenic nature of As. Exposure of plants to As, even at very low concentration, can cause many morphological, physiological, and biochemical changes. The recent research on As in the soil-plant system indicates that As toxicity to plants varies with its speciation in plants (e.g., arsenite, As(III); arsenate, As(V)), with the type of plant species, and with other soil factors controlling As accumulation in plants. Various plant species have different mechanisms of As(III) or As(V) uptake, toxicity, and detoxification. This review briefly describes the sources and global extent of As contamination and As speciation in soil. We discuss different mechanisms responsible for As(III) and As(V) uptake, toxicity, and detoxification in plants, at physiological, biochemical, and molecular levels. This review highlights the importance of the As-induced generation of reactive oxygen species (ROS), as well as their damaging impacts on plants at biochemical, genetic, and molecular levels. The role of different enzymatic (superoxide dismutase, catalase, glutathione reductase, and ascorbate peroxidase) and non-enzymatic (salicylic acid, proline, phytochelatins, glutathione, nitric oxide, and phosphorous) substances under As(III/V) stress have been delineated via conceptual models showing As translocation and toxicity pathways in plant species. Significantly, this review addresses the current, albeit partially understood, emerging aspects on (i) As-induced physiological, biochemical, and genotoxic mechanisms and responses in plants and (ii) the roles of different molecules in modulation of As-induced toxicities in plants. We also provide insight on some important research gaps that need to be filled to advance our scientific understanding in this area of research on As in soil-plant systems.

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Quinoa (Chenopodium quinoa Willd.), traditionally called the mother of grains, has the potential to grow under high temperatures and drought, tolerating levels regarded as stresses in other crop species. A pot experiment was conducted in a climate chamber to investigate the potential of quinoa tolerance to increasing drought and temperature. Quinoa plants were subjected to three irrigation and two temperature regimes. At low temperature, the day/night climate chamber temperature was maintained at 18/8 °C and 25/20 °C for high temperature throughout the treatment period. The irrigation treatments were full irrigation (FI), deficit irrigation (DI) and alternate root‐zone drying (ARD). FI plants were irrigated daily to the level of the pot's water‐holding capacity. In DI and ARD, 70 % water of FI was applied either to the whole pot or to one side of the pot alternating, respectively. The results indicated that plant height and shoot dry weight significantly decreased by ARD and DI compared to FI treatment both at low and at high temperatures. However, plants in ARD treatment showed significantly higher plant height and shoot dry weight compared to DI especially at higher temperature, which is linked to increased xylem ion content. Higher quinoa plant growth in ARD was associated with increase in water‐use efficiency (WUEi) due to higher abscisic acid concentration and higher nutrient contents compared to DI. From results, it can be concluded that quinoa plant growth is favoured by high temperature (25/20 °C) and ARD is an effective irrigation strategy to increase WUE in drought prone areas.

Quinoa is a facultative halophytic seed crop of increasing interest worldwide. Its performance declines under high salinity but can be improved by using halotolerant plant growth-promoting bacteria (PGPB) containing multi-traits, i.e. ACC-deaminase activity, exopolysaccharide secretion and auxin production. This study focussed on improving the productivity of quinoa through the use of six plant growth-promoting bacterial strains (both endophytic and rhizosphere). These were screened by conducting osmoadaptation assay, and the two most halotolerant strains (Enterobacter sp. (MN17) and Bacillus sp. (MN54)) were selected. These two strains were evaluated for their effects on growth, physiological characters and yield of quinoa. At the five leaf stage plants were irrigated with saline water having either 0 or 400 mM NaCl. The results indicated that saline irrigation significantly decreased the growth of quinoa, whereas inoculation of plants with MN17 and MN54 mitigated the negative effects of salinity by improving plant water relations and decreasing Na+ uptake, which consequently, reduced osmotic and ionic stress. Strain MN54 performed better than MN17, which might be because of its better growth promoting traits and higher rhizosphere colonisation efficiency than MN17. Our results suggest that growth and productivity of quinoa could be improved by inoculating with highly tolerant PGPB strain in salt-affected soils.

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The present study examined novel wheat straw biochar (WSB) and acid treated wheat straw biochar (AWSB) for cadmium removal from contaminated water. A series of batch and column scale experiments was conducted to evaluate the potential of WSB and AWSB for cadmium removal at different biochar dosage (0.5–8 g/L), initial cadmium concentration (5–100 mg/L), solution pH (2–8) and contact time (5–180 min). Results revealed that cadmium adsorption decreased by increasing biochar dosage from 0.5 to 8 g/L; however, optimum dosage for maximum (99%) removal of cadmium was 2 g/L by WSB and 1 g/L by AWSB. Enhanced cadmium removal potential by AWSB is attributed to increased surface area, microporosity and variation in functional groups. Equilibrium experimental data was well described by Freundlich adsorption isotherm whereas kinetic data were better explained with pseudo-second order model. Both WSB and AWSB have shown good adsorption capacity of 31.65 mg/g and 74.63 mg/g, respectively, that is comparable with other costly adsorbents. Columns packed with WSB and AWSB at laboratory scale have also shown good retention of cadmium with excellent reusability. These findings indicate that WSB especially AWSB could be a promising, cost-effective and environmental friendly strategy for the removal of metals from contaminated water.

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