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Arsenic (As) is a major threat to the environment and human health due to its toxicity and carcinogenicity. Occurrence of alarming concentrations of As in water and soil leads to its bioaccumulation in crops which is a major health concern globally. Rice (Oryza sativa) is a staple food for a large population staying in As contaminated areas so, it is of utmost importance to reduce As levels in rice, especially grains. Amongst several strategies in practice, biotechnology may provide an effective option to reduce As accumulation in rice grains. Genetic engineering can be a viable approach to exploit potential genes playing roles in As metabolism pathway in plants. Besides, developing low As accumulating rice varieties through breeding is also an important area. Identifying genotypic variation in rice is a crucial step toward the development of a safe rice cultivar for growing in As-affected areas. Significant genotypic variation has been found in rice varieties for As accumulation in grains and that is attributable to differential expression of transporters, radial oxygen loss, and other regulators of As stress. This review provides recent updates on the research advances leading to transgenic and breeding approaches adopted to reduce As levels in rice, especially grains. Arsenic (As) contamination in water, soil, and crops is creating a difficult situation for the large population across the globe. Various efforts are being made to reduce As levels in rice as it is a staple crop. This review presents recent biotechnological advances toward the development of low As accumulating rice. The review shall be an important information resource for the readers on the topic. [ABSTRACT FROM AUTHOR]

The present study was aimed to analyze the effects of external Zn supply on arsenic (As) toxicity inHydrilla verticillata(L.f.) Royle. The plants were exposed to arsenite (AsIII; 10 μM) with or without 50 and 100 μM Zn. The level of As accumulation (μg g−1dw) after 2 and 4 days was not significantly affected by Zn supply. The plants showed a significant stimulation of the thiol metabolism (nonprotein thiols, cysteine, glutathione-S-transferase activity) upon As(III) exposure in the presence of Zn as compared to As(III) alone treatment. Besides, they did not experience significant toxicity, measured in terms of hydrogen peroxide and malondialdehyde accumulation, which are the indicators of oxidative stress. The minus Zn plants suffered from oxidative stress probably due to insufficient increase in thiols to counteract the stress. Stress amelioration by Zn supply was also evident from antioxidant enzyme activities, which came close to control levels with increasing Zn supply as compared to the increase observed in As(III) alone treatment. Variable Zn supply also modulated the level of photosynthetic pigments and restored them to control levels. In conclusion, an improved supply of Zn to plants was found to augment their ability to withstand As toxicity through enhanced thiol metabolism. [ABSTRACT FROM AUTHOR]

Helianthus annuus is a potential metal accumulator plant, which can find application in cadmium (Cd) phytoremediation and provide economic gains in terms of oil yield. This study is focused on Cd accumulation analysis, physiological and biochemical responses of five varieties of H. annuus (DRSF-108, DRSF-113, LSFH-171, Phule Bhaskar and KBSH-44). Plantlets of all varieties were treated with various Cd concentrations (10, 50, 100, 300 and 500 mg kg−1) for 20, 40 and 60 days. DRSF-108 showed the maximum total Cd accumulation (430.52 mg kg−1) in whole plant while minimum accumulation was observed in KBSH-44 (150.66 mg kg−1) at 500 mg kg−1 Cd after 60 days. The highest level of proline and polyphenol in DRSF-108 were 27.206 µmol g−1 fw and 6.86 mg g−1 fw, respectively. Antioxidant enzymes (catalase, ascorbate peroxidase and glutathione reductase) also showed increased activity in response to Cd treatment. SEM-EDX analysis of potential accumulator genotype, DRSF-108, showed the distribution of intracellular Cd into plant tissues. Therefore, it is concluded that among five varieties, DRSF-108 was the most potential Cd accumulator and had a higher capacity for Cd tolerance compared to other varieties. Our findings may allow us to extend variety DRSF-108 for sustainable farming and Cd remediation. Phytoremediation of environmental contaminants is a promising strategy, however, the success depends on the use of suitable plants. Helianthus annuus is a good phytoremediator plant and the use of most promising genotype is desirable. This work evaluated five genotypes of H. annuus for cadmium accumulation and identified the best variety, DRSF-108 that can be used for cadmium remediation. The work shall pave way for field application of sunflower plants in cadmium remediation. [ABSTRACT FROM AUTHOR]

Arsenic (As) contamination of the environment has emerged as a serious problem. Consequently, there is an urge to understand plants’ responses to As. The analysis of various hypertolerant and hyperaccumulator plants and comparison of their responses with non-tolerant and nonaccumulators have provided valuable information about the mechanisms of As tolerance and detoxification. Therefore, we understand why most of the pteridophytes are able to hyperacumulate As, why it is difficult to find hyperaccumulators among angiosperms and why rice is able to translocate As to its grains more efficiently than any other cereal crop. This information can be employed to generate As hyperaccumulators in angiosperms and to develop safe cultivars of rice for human consumption through biotechnological approaches. Although measurable success, in terms of application in the field, has so far not been achieved, transgenic research has yielded promising results, which shed light on the approaches to be taken up in future endeavor. In this review, we discuss the mechanisms of As tolerance and detoxification in plants and transgenic research conducted. [ABSTRACT FROM PUBLISHER]

Selenium (Se) is an essential element for many animals including humans, prokaryotes and a few green algae. For plants, Se essentiality is yet to be demonstrated. Nevertheless, it is well recognized that Se is a beneficial element for plants. For all organisms, while, a narrow range of Se is beneficial, at elevated levels it becomes toxic. This is due to accumulation of various toxic inorganic and organic Se forms during Se metabolism as well as nonspecific replacement by Se of chemically similar sulfur (S) analogs. Interestingly, Se can act both as an antioxidant and a pro-oxidant. Hence, Se chemistry and metabolism play crucial roles in determining its effects at specific concentration in an organism. A lot of knowledge has been gained regarding Se metabolites, however, the functions of many of these metabolites are yet to be resolved. Other Se containing metabolites and proteins might yet be awaiting their identification. Future research in this direction would pave the way towards identification of Se as an essential element for plants too. This review discusses the various aspects of Se uptake and metabolism with a major focus on functions of Se-containing metabolites in plants. [ABSTRACT FROM AUTHOR]

Unexpected bioaccumulation and biomagnification of heavy metal(loid)s (HMs) in the environment have become a predicament for all living organisms, including plants. The presence of these HMs in the plant system raised the level of reactive oxygen species (ROS) and remodeled several vital cellular biomolecules. These lead to several morphological, physiological, metabolic, and molecular aberrations in plants ranging from chlorosis of leaves to the lipid peroxidation of membranes, and degradation of proteins and nucleic acid including the modulation of the enzymatic system, which ultimately affects the plant growth and productivity. Plants are equipped with several mechanisms to counteract the HMs toxicity. Among them, seed priming (SP) technology has been widely tested with the use of several inorganic chemicals, plant growth regulators (PGRs), gasotransmitters, nanoparticles, living organisms, and plant leaf extracts. The use of these compounds has the potential to alleviate the HMs toxicity through the strengthening of the antioxidant defense system, generation of low molecular weight metallothionein's (MTs), and phytochelatins (PCs), and improving seedling vigor during early growth stages. This review presents an account of the sources, uptake and transport, and phytotoxic effects of HMs with special attention to different mechanism/s, occurring to mitigate the HMs toxicity in plants employing SP technology. Novelty statement: To the best of our knowledge, this review has delineated the consequences of HMs on the crucial plant processes, which ultimately affect plant growth and development. This review also compiled the up to dated information on phytotoxicity of HMs through the use of SP technology, this review discussed how different types of SP approaches help in diminishing the concentration HMs in plant systems. Also, we depicted mechanisms, represent how HMs transport and their actions on cellular levels, and emphasized, how diverse SP technology effectiveness in the mitigation of plants' phytotoxicity in unique ways. [ABSTRACT FROM AUTHOR]

The present study was planned to delineate the role of antioxidants and different functional groups ofRicinus communisandBrassica junceain the tolerance mechanisms toward cadmium (Cd) for phytoremediation. Application of Cd caused a reduction in dry biomass of 53.84% and 26.58% in root and 45.33% and 33.84% in shoots ofB. junceaandR. communis, respectively. Antioxidant enzymes, namely superoxide dismutase, catalase, ascorbate peroxidase, guaiacol peroxidase, glutathione reductase and glutathione-S-transferase, and metabolites (proline) increased in both the species due to Cd exposure. The metal caused substantial changes in the functional groups present in the roots and leaves of the plants. A number of new peaks appeared in the Cd-treated plants, which indicate the production of the compounds responsible for the metal tolerance of these plants.R. communishas been found to possess a good antioxidant defense system against Cd stress and may be used for the phytoremediation of metal-contaminated soils in place of edible crops, which enhance the risk of contaminating the food chain. It has been observed thatR. communisaccumulated 213.39 and 335.68 mg Cd in roots and shoots, respectively, whereasB. junceaaccumulated 28.19 and 310.15 mg Cd in the roots and shoots, respectively. [ABSTRACT FROM AUTHOR]