The contamination of soils with heavy metals and its associated hazardous effects are a thrust area of today’s research. Rapid industrialization, emissions from automobiles, agricultural inputs, improper disposal of waste, etc., are the major causes of soil contamination with heavy metals. These contaminants not only contaminate soil but also groundwater, reducing agricultural land and hence food quality. These contaminants enter the food chain and have a severe effect on human health. It is important to remove these contaminants from the soil. Various economic and ecological strategies are required to restore the soils contaminated with heavy metals. Phytoremediation is an emerging technology that is non-invasive, cost-effective, and aesthetically pleasing. Many metal-binding proteins (MBPs) of the plants are significantly involved in the phytoremediation of heavy metals; the MBPs include metallothioneins; phytochelatins; metalloenzymes; metal-activated enzymes; and many metal storage proteins, carrier proteins, and channel proteins. Plants are genetically modified to enhance their phytoremediation capacity. In Arabidopsis, the expression of the mercuric ion-binding protein in Bacillus megaterium improves the metal accumulation capacity. The phytoremediation efficiency of plants is also enhanced when assisted with microorganisms, biochar, and/or chemicals. Removing heavy metals from agricultural land without challenging food security is almost impossible. As a result, crop selections with the ability to sequester heavy metals and provide food security are in high demand. This paper summarizes the role of plant proteins and plant–microbe interaction in remediating soils contaminated with heavy metals. Biotechnological approaches or genetic engineering can also be used to tackle the problem of heavy metal contamination.

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Phytoremediation technologies and their mechanism for removal of heavy metal from contaminated soil: An approach for a sustainable environment

The roles of Salvia miltiorrhiza-derived carbon dots involving in maintaining quality by delaying senescence of postharvest flowering Chinese cabbage.

Cadmium (Cd) soil contamination is a global problem for food security due to its ubiquity, toxicity at low levels, persistence, and bioaccumulation in living organisms. Humans' intake of heavy metals is usually due to direct contact with contaminated soil, through the food chain (Cd accumulation in crops and edible plants) or through drinking water in cases of coupled groundwater-surface water systems. Phytoextraction is one of the eco-friendly, sustainable solutions that can be used as a method for soil clean-up with the possibility of re-use of extracted metals through phytomining. Phytoextraction is often limited by the tolerance level of hyperaccumulating plants and the restriction of their growth. Mechanisms of hyperaccumulation of heavy metals in tolerant species have been studied, but there are almost no data on mechanisms of further improvement of the accumulation capacity of such plants. Priming can influence plant stress tolerance by the initiation of mild stress cues resulting in acclimation of the plant. The potential of plant priming in abiotic stress tolerance has been extensively investigated using different types of molecules that are supplemented exogenously to plant organs (roots, leaves etc.), resulting in enhanced tolerance of abiotic stress. This review focuses on mechanisms of enhancement of plant stress tolerance in hyperaccumulating plants for their exploitation in phytoextraction processes. This article is protected by copyright. All rights reserved.

Thinking for the future: Phytoextraction of cadmium using primed plants for sustainable soil clean-up.

The bagging of fruits provides efficient protection from high-intensity sunlight and improves fruit color and quality. However, bagged fruit suddenly exposed to bright light can cause sunburn and destroys the peel cell structure. In this study, fruits from ten-year-old apple trees of ‘Gala’ variety were debagged, and the effect of sunburn on fruits was divided into: (1) normal peels (BFN), (2) peels with albefaction (BFA), and (3) browning (BFB). The non-bagging fruits (NBF) were set as a control to study the physiological characteristics of apple fruits with different levels of sunburn. Our results showed that in the early stages of debagged fruits’ sunburn, the cell structure of the peel was partially destroyed, the color of the injured fruit surface turned white, and the peroxidation in the cell membrane of the peel increased. Initially, the fruit improved its photosynthetic protection ability, and the activity of antioxidants and phenolics was enhanced, to cope with external injury. However, with the increase in duration of high-intensity sunlight, the cell structure of the peel was severely damaged, and the increase in membrane peroxidation resulted in brown coloration of fruits. Under the same conditions, the photoprotection ability and antioxidant enzyme activity of non-bagged fruits showed higher levels. In conclusion, the non-bagged fruits were more adaptable to high-intensity sunlight as compared to debagged fruits.

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Physiological Characteristics of Sunburn Peel after Apple Debagged

The aim of this study is to examine the thiol species for the high cadmium (Cd) tolerance of spinach and provide information for the improvement of soil utilization. The spinach was cultured in aqueous solution with concentrations of Cd ranging from 1 to 9 mg/L. The time responses of glutathione (GSH) and phytochelatins (PCs, PC2-PC4) in the tissues of spinach were monitored via HPLC–MS/MS, and the concentrations of Cd in the roots, shoots and leaves were detected by ICP–OES. Data were analyzed via one-way ANOVA and Spearman correlation to assess the relationships among the types of thiols and the changes between types of thiols and Cd. As Cd stress increased, Cd concentrations in tissues also increased. The total thiol contents responded to Cd stresses with correlations r ranging from 0.394 (root), 0.520 (shoot) to 0.771 (leaf) (p < 0.01). GSH and PC3 were dominant on most of the days under Cd stress. The correlation r between improvements in GSH and increments of Cd concentration in roots was −0.808 (p < 0.01), and r between changes in PC3 and changes in Cd concentrations in leaves was −0.503 (p < 0.01). No correlation can be found between GSH and the subtypes of PCs in shoots, but strong positive correlations within the subtypes of PCs. Thiols can be produced in different tissues of spinach, while the shoots are only a transport tissue for GSH.

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The Response of Thiols to Cadmium Stress in Spinach (Spinacia Oleracea L.)

Foliar application of flavonoids (rutin) regulates phytoremediation efficiency of Amaranthus hypochondriacus L. by altering the permeability of cell membranes and immobilizing excess Cd in the cell wall

Selenium alleviates toxicity in Amaranthus hypochondriacus by modulating the synthesis of thiol compounds and the subcellular distribution of cadmium.

Rutin is a flavonoid with strong antioxidative effects on plant metabolism that facilitates resistance to environmental stress. The effect of foliar rutin on cadmium (Cd) uptake in Amaranthus hypochondriacus (K472) was studied. The results showed that a foliar spray of rutin alleviated Cd toxicity, promoted plant growth, improved Cd transfer to and storage in aerial plant parts and Cd accumulation with positive effects over time. A rutin concentration of 1.5 mg/mL showed the strongest promotion effect: the biomass and Cd content were increased at 13 days by 68.62% and 405.54% compared to 3 days, respectively, whereas a high concentration of rutin (5 mg/mL) inhibited plant growth and hindered Cd absorption. Two stages of Cd detoxification were identified in K472 after appropriate rutin application. First, an antioxidant system including an enzymatic antioxidant (superoxide dismutase [SOD]) and nonenzymatic antioxidants (glutathione [GSH] and flavonoids) was activated to enhance plant stress resistance. Quercetin and phytochelatin (PC) synthesis were then enhanced to perform detoxification synergistically with the antioxidant system to improve stress tolerance and achieve stable Cd detoxification. The results demonstrated that appropriately prolonging the application time of exogenous rutin to K472 is an effective way to improve the Cd remediation efficiency.

Foliar spray with rutin improves cadmium remediation efficiency excellently by enhancing antioxidation and phytochelatin detoxification of Amaranthus hypochondriacus.

Na Li

Papers

Foliar application of flavonoids (rutin) regulates phytoremediation efficiency of Amaranthus hypochondriacus L. by altering the permeability of cell membranes and immobilizing excess Cd in the cell wall

Selenium alleviates toxicity in Amaranthus hypochondriacus by modulating the synthesis of thiol compounds and the subcellular distribution of cadmium.

Foliar spray with rutin improves cadmium remediation efficiency excellently by enhancing antioxidation and phytochelatin detoxification of Amaranthus hypochondriacus.