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The present study identified inverse relationships between nickel (Ni) levels and growth, photosynthesis and physio-biochemical attributes, but increasing levels of Ni stress enhanced methylglyoxal, electrolyte leakage, hydrogen peroxide, and lipid peroxidation content. Exogenous application of salicylic acid (SA) (10 -5  M) ameliorated the ill-effects of Ni by restoring growth, photosynthesis and physio-biochemical attributes and increasing the activities of enzymes associated with antioxidant systems, especially the ascorbate-glutathione (AsA-GSH) cycle and glyoxalase system. In addition, SA application to Ni-stressed plants had an additive effect on the activities of the ascorbate and glutathione pools, and the AsA-GSH cycle enzymes (ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase), superoxide dismutase, catalase, glutathione S-transferase, and osmolyte biosynthesis). This trend also follows in glyoxalase system viz. glyoxalase I and glyoxalase II enzymes. Nevertheless, exogenous SA supplementation restored mineral nutrient contents. Principal component analysis showed that growth, photosynthesis, and mineral nutrient parameters were positively correlated with each other and negatively correlated with antioxidant enzymes and oxidative stress biomarkers. Hence, SA is an alternative compound with potential application in the phytoremediation of Ni., (Copyright © 2019 Elsevier Inc. All rights reserved.)

We examined effects of methyl jasmonate (MeJ), with and without N, for the alleviation of the adverse effects of 150 mg kg−1 CdCl2 stress in mentholmint (Mentha arvensis) plants. Exposure of mentholmint plants to Cd stress reduced morphological growth parameters, photosynthetic attributes, chlorophyll content and mineral nutrient assimilation rate. Cd stress significantly increased endogenous leaf and root Cd content by 67.10% and 83.05%, respectively, electrolyte leakage by 67.26%, hydrogen peroxide (H2O2) by 56.66% and malondialdehyde content by 53.97% over that of the control. Cd stress upregulated activities of antioxidant enzymes and increased osmolyte concentration. Application of 1 µM MeJ to Cd-stressed plants partially alleviated the Cd-induced oxidative stress; however, co-application of MeJ with inorganic N reversed the detrimental effects more than did MeJ or N alone. Combined application of MeJ + N further elevated the osmolyte levels and markedly increased mineral nutrient contents and nitrogen use efficiency. MeJ + N significantly reduced the production of reactive oxygen species (ROS) directly or indirectly through higher stimulation of ROS-scavenging enzymes and decreased the root-to-shoot Cd rate of translocation. Cd-induced stomatal inhibition was recovered by MeJ and N. Our study demonstrated the regulatory role of MeJ and N in overcoming Cd stress in mentholmint plants. The study is the first report of regulatory interaction of the exogenous phytohormone (MeJ) with inorganic nutrient (N) for enhancing Cd stress tolerance in mentholmint plants, the same concept can be used for remediation of toxic metal/metalloids in agricultural production. [ABSTRACT FROM AUTHOR]

Multi-walled carbon nanotubes (MWCNTs) have recently attracted huge attention to their impacts on the environment and plants. Therefore, this experiment was conducted to investigate the responses of lead (Pb) and cadmium (Cd) exposed pot marigold plants to various levels of MWCNT. Calendula officinalis (L.) seedlings were cultivated in Pb and Cd-polluted soils with exposure to 0, 50, 100, 250, 500 and 1000 mg L−1 of MWCNT. The results demonstrated that foliar-applied MWCNT up to 250 mg L−1 not only alleviated Pb and Cd-induced toxicity by reducing oxidative damage and boosting both enzymatic and non-enzymatic antioxidant defense system but also promoted the phytoremediation property of pot marigold plants by enhancing the accumulation of both Pb and Cd from the soil. Interestingly, oxidative damage exacerbation and both Pb and Cd accumulation reduction were noticed in pot marigold seedlings exposed to 500 and 1000 mg L−1 MWCNTs. The findings of this study clearly showed that the use of appropriate concentrations of MWCNTs in increasing the phytoremediation properties of pot marigold was justified, while the use of high concentrations is toxic to the plant and intensifies the toxic effects of heavy metals (HMs) on plant physiology. This study provides a novel method to facilitate the phytoremediation of HMs polluted soils using MWCNT as well as explores the potential risks of these nanoparticles to the plants. • The foliar-application of MWCNT alleviated Pb and Cd-induced toxicity. • MWCNTs reduced oxidative damage and boosted antioxidant defense system. • The lower doses of MWCNTs could be used for increasing phytoremediation properties to Calendula officinalis (L.). [ABSTRACT FROM AUTHOR]

• The effects of graded Cd stress on growth, yield and biochemical characteristics of eight pea varieties were studied. • Both Cd treatments had significant negative impact on different vegetative and reproductive traits of pea varieties. • Cd accumulated differentially in stem, leaves, pods and seeds in different pea varieties. • Out of eight, three varieties performed significantly better for yield and yield related traits when they were grown under Cd stress. Cadmium (Cd) contamination of soil poses a major hazard to plants by affecting their morphology, physiology, and molecular structure, resulting inroot and leaf necrosis, leaf chlorosis, and reduction in tissue and organ growth. Due to pea's ability to fix their own nitrogen from the atmosphere through a symbiotic relationship with Rhizobium , pea production may be possible in Cd contaminated soils, but varietal response may vary. That's why an experiment was carried out to check the effect of Cd stress on growth, yield and biochemical characteristics of eight pea varieties (Meteor, Green cross, Sultan, Green gold, Sarsabz, Lina, Climax and Supreme). Three cadmium levels (0, 50 and 100 ppm) were applied to the soil in planters, before sowing of eight pea varieties. The results showed that both Cd treatments had significant negative impact on different vegetative and reproductive traits of pea varieties, particularly Cd @ 100ppm that significantly decreased plant height, number of leaves, leaf area, plant biomass, pod fresh weight, pod length and pod yield per plant.The accumulation of Cd in stem + leaves, pod and seed was significantly different for varieties and Cd treatments with highest Cd concentration was observed in plants grown in 100 ppm Cd level. As Cd level increased, all varieties showed significant decrease in chlorophyll contents and peroxidase activity; whilst superoxide dismutase activity was increased significantly under similar conditions. Overall results indicated that three varieties viz. Green Cross, Green Gold and Lina performed significantly better for yield and yield related traits when they were grown in control and 50 ppm Cd compared to100 ppm Cd level. Moreover, among all pea varieties, Supreme variety showed minimum accumulation of Cd (0.8 mg kg−1) in pea seeds as per WHO permissible limits. It can be concluded from results that four pea varieties (Supreme, Green Cross, Green Gold and Lina) can be grown in soils with mild (50 ppm) Cd contamination, particularly Supreme that accumulates less Cd in consumable part, i.e. seeds. [ABSTRACT FROM AUTHOR]

Chromium is a serious heavy metal (HM) and its concentration in plant-soil interface is soaring due to anthropogenic activities, unregulated disposals, and lack of efficient treatments. High concentration of Cr is toxic to ecosystems and human health. Cr stress also diminishes the plant performance by changing the plant's vegetative and reproductive development that ultimately affects sustainable crop production. Silicon (Si) is the second-most prevalent element in the crust of the planet, and has demonstrated a remarkable potential to minimize the HM toxicity. Amending soils with Si mitigates adverse effects of Cr by improving plant physiological, biochemical, and molecular functioning and ensuring better Cr immobilization, compartmentation, and co-precipitation. However, there is no comprehensive review on the role of Si to mitigate Cr toxicity in plants. Thus, in this present review; the discussion has been carried on; 1) the source of Cr, 2) underlying mechanisms of Cr uptake by plants, 3) how Si affects the plant functioning to reduce Cr toxicity, 4) how Si can cause immobilization, compartmentation, and co-precipitation 5) strategies to improve Si accumulation in plants to counter Cr toxicity. We also discussed the knowledge gaps and future research needs. The present review reports up-to-date knowledge about the role of Si to mitigate Cr toxicity and it will help to get better crop productivity in Cr-contaminated soils. The findings of the current review will educate the readers on Si functions in reducing Cr toxicity and will offer new ideas to develop Cr tolerance in plants through the use of Si. • Cr as a heavy metal accumulates indiscriminately in plant-soil interface. • Cr induces ionic, osmotic and oxidative stress in plants. • Si acts as a potential signaling inorganic elicitor in plants. • Si shows a potential trade-off with other molecules to impart stress tolerance. • The review highlights current knowledge of Si to mitigate Cr phyto-toxicity to get enhanced crop productivity. [ABSTRACT FROM AUTHOR]