Interactive zinc, iron, and copper-induced phytotoxicity in wheat roots

Phytoaccumulation of zinc and its associated impact on the growth performance and tolerance index of six non-food crop plants grown in Zn-contaminated soil

Crop plant remediation and detoxification of Zn-contaminated soils may pose a significant threat to food safety and, thus, human health. Therefore, the current study was carried out to assess the ability of six non-food crop plants (NFCP); Zea mays L. cultivar 360 (T360), Z. mays cultivar 123 (T123), Helianthus annuus L., Brassica juncea (L.) Czern., Ricinus communis L., and Simmondsia chinensis (Link) C.K. Schneid to remediate and restore Zn-contaminated soils. The investigated plants tolerate 150 mg/kg of Zn content of the soil, where they had tolerance index (TI) > 1 for all growth criteria, except the root dry weight (DW) of S. chinensis. Z. mays T123 and R. communis were the most susceptible plants, while B. juncea and S. chinensis were moderately tolerant, while H. annuus was the most tolerant to high Zn concentrations in a growing medium. Increasing the soil Zn content led to a significant increase (p < 0.05) in Zn concentration in the various tissues of the six NFCPs. The studied NFCP did not translocate Zn to their grains/seeds; consequently, they can be used safely for Zn-contaminated soils. The Zn content in root and shoot was negatively correlated with the TI of their length and weight, while the translocation factor (TF) of Zn from root to shoot was positively correlated to the TI of the root length and weight. The six studied NFCPs were arranged based on their phytoremediation efficiency as follows: B. juncea (31.86%) > Z. mays T123 (31.14%) > Z. mays T360 (27.59%) > H. annuus (20.85%) > S. chinensis (20.29%) > R. communis (15.3%). All tested NFCPs accumulated significant concentrations of Zn in their roots and shoots, a high Zn uptake potential, and biomass at 150-450 mg/kg of Zn treatments, indicating that these plants are good candidates for the implementation of a new strategy of cultivating NFCP for phytoremediation of Zn-contaminated soils.

Phytotoxicity of particulate matter from controlled burning of different plastic waste types

According to careful estimations, open burning of plastic waste affects app. 2 billion people worldwide. While human health risks have become more and more obvious, much less information is available on the phytotoxicity of these emissions. In our study phytotoxicity of particulate matter samples generated during controlled combustion of different plastic waste types such as polyvinyl chloride (PVC), polyurethane (PUR), polypropylene (PP), polystyrene (PS) and polyethylene (PE) was evaluated based on peroxidase levels. While different samples showed different concentration-effect relationship patterns, higher concentration(s) caused decreased peroxidase activities in each sample indicating serious damage.

Multi-omics analyses on the response mechanisms of 'Shine Muscat' grapevine to low degree of excess copper stress (Low-ECS)

Copper stress is one of the most severe heavy metal stresses in plants. Grapevine has a relatively higher copper tolerance than other fruit crops. However, there are no reports regarding the tolerance mechanisms of the 'Shine Muscat' ('SM') grape to a low degree of excess copper stress (Low-ECS). Based on the physiological indicators and multi-omics (transcriptome, proteome, metabolome, and microRNAome) data, 8 h (h) after copper treatment was the most severe stress time point. Nonetheless, copper stress was alleviated 64 h after treatment. Cu ion transportation, photosynthesis pathway, antioxidant system, hormone metabolism, and autophagy were the primary response systems in 'SM' grapevine under Low-ECS. Numerous genes and proteins, such as HMA5, ABC transporters, PMM, GME, DHAR, MDHAR, ARGs, and ARPs, played essential roles in the 'SM' grapevine's response to Low-ECS. This work was carried out to gain insights into the multi-omics responses of 'SM' grapevine to Low-ECS. This study provides genetic and agronomic information that will guide better vinery management and breeding copper-resistant grape cultivars.

Towards a Soil Remediation Strategy Using Biochar: Effects on Soil Chemical Properties and Bioavailability of Potentially Toxic Elements

Soil contamination with potentially toxic elements (PTEs) is considered one of the most severe environmental threats, while among remediation strategies, research on the application of soil amendments has received important consideration. This review highlights the effects of biochar application on soil properties and the bioavailability of potentially toxic elements describing research areas of intense current and emerging activity. Using a visual scientometric analysis, our study shows that between 2019 and 2020, research sub-fields like earthworm activities and responses, greenhouse gass emissions, and low molecular weight organic acids have gained most of the attention when biochar was investigated for soil remediation purposes. Moreover, biomasses like rice straw, sewage sludge, and sawdust were found to be the most commonly used feedstocks for biochar production. The effect of biochar on soil chemistry and different mechanisms responsible for PTEs' immobilization with biochar, are also briefly reported. Special attention is also given to specific PTEs most commonly found at contaminated soils, including Cu, Zn, Ni, Cr, Pb, Cd, and As, and therefore are more extensively revised in this paper. This review also addresses some of the issues in developing innovative methodologies for engineered biochars, introduced alongside some suggestions which intend to form a more focused soil remediation strategy.

Zinc biosorption by Dunaliella sp. AL-1: Mechanism and effects on cell metabolism

Phycoremediation is being considered as an eco-friendly and safe technology for toxics eradication from contaminated aquatic systems. The zinc biosorption capacity of Dunaliella sp. AL-1 was demonstrated. Zinc impacted cell growth and photosynthetic pigments accumulation showing exposure time and concentration-dependent effects. The investigation of the antioxidant protective response to zinc exposition proved a stimulation of guaiacol peroxidase (GPX) activity and an increased rate of total phenolics, flavonoids, condensed tannins and glutathione (GSH). The Box-Behnken design was used to optimize zinc removal conditions by Dunaliella sp. AL-1 strain. The maximum experimental zinc uptake was obtained when zinc concentration, algae dose, initial pH, and contact time were set at 25 mg/L, 0.5 g/L, 7.59 and 13 h 43 min, respectively. Under completely optimized conditions, the fraction of zinc removed intracellularly was much lower than the adsorbed on the cell surface. FTIR analysis Dunaliella sp. AL-1 biomass demonstrated that several functional groups as OH, CH₂, CO, PO, COO and CO may participate in the biosorption process. A comparative proteomic analysis through nano-HPLC coupled to LC-MS/MS, was performed from pre- and post-zinc treatments cells. Among 199 identified proteins, 60 were differentially expressed of which 41 proteins were down-regulated against 19 up-regulated ones. Target proteins have been demonstrated to be implicated in different metabolic processes mainly photosynthesis and antioxidant defenses.

Effects of exogenous lanthanum(III) exposure on the positive interaction between mutually beneficial populations

Rare earth elements (REEs) are widely used in various fields, and their accumulation has been reported to pose environmental risks. Most studies confirmed the damage of excessive REE exposure to individual plants; however, little attention has been given to their effects on plant populations. A positive interaction indicates a mutually beneficial relationship between two populations, which is beneficial to the survival and growth of the populations. However, it remains unknown whether exogenous REEs affect the positive interactions between populations. This study investigated the effects of exogenous lanthanum(III) [La(III)] exposure on the positive interaction between soybean (Glycine max L.) and wheat (Triticum aestivum L.) populations by their modules. At normal nutrient level (½-strength Hoagland), the inhibition of excessive La(III) on population modules decreased with increasing population density. Decreases of 39.26 to 1.05% for soybean and 41.45 to 2.41% for wheat indicated the inhibition of La(III) on the positive interaction of both populations weakened with increasing population density. At low nutrient level (¼-strength Hoagland), the inhibition of excessive La(III) on population modules increased with increasing population density. Decreases of 5.82-57.14% for soybean and 4.22-59.04% for wheat indicated the inhibition of La(III) on the positive interaction of both population was strengthened with increasing population density. In summary, the inhibitory effects of exogenous La(III) exposure on the positive interaction between populations vary with both nutrient level and population density. This is a new factor that needs to be considered when evaluating the safety risks of REEs in the environment.

Zinc toxicity alters the photosynthetic response of red alga Pyropia yezoensis to ocean acidification

The globally changing environmental climate, ocean acidification, and heavy metal pollution are of increasing concern. However, studies investigating the combined effects of ocean acidification and zinc (Zn) exposure on macroalgae are very scarce. In this study, the photosynthetic performance of the red alga Pyropia yezoensis was examined under three different concentrations of Zn (control, 25 (medium), and 100 (high) μg L^-1) and pCO₂ (400 (ambient) and 1000 (high) μatm). The results showed that higher Zn concentrations resulted in increased toxicity for P. yezoensis, while ocean acidification alleviated this negative effect. Ocean acidification increased the relative growth rate of thalli under both medium and high Zn concentrations. The net photosynthetic rate and respiratory rate of thalli also significantly increased in response under ocean acidification, when thalli were cultured under both medium and high Zn concentrations. Malondialdehyde levels decreased under ocean acidification, compared to ambient CO₂ conditions and either medium or high Zn concentrations. The activity of superoxide dismutase increased in response to high Zn concentrations, which was particularly apparent at high Zn concentration and ocean acidification. Immunoblotting tests showed that ocean acidification increased D1 removal, with increasing expression levels of the PSII reaction center proteins D2, CP47, and RbcL. These results suggested that ocean acidification could alleviate the damage caused by Zn exposure, thus providing a theoretical basis for a better prediction of the impact of global climate change and heavy metal contamination on marine primary productivity in the form of seaweeds.

Effects of nutrient level and planting density on population relationship in soybean and wheat intercropping populations

A positive interaction between plant populations is a type of population relationship formed during long-term evolution. This interaction can alleviate population competition, improve resource utilization in populations, and promote population harmony and community stability. However, cultivated plant populations may have insufficient time to establish a positive interaction, thereby hindering the formation of the positive interaction. As current studies have not fully addressed these issues, our study established soybean/wheat intercropping populations beneficial for growth and explored the effects of nutrient level and planting density on the positive interaction between the two crops. Changes across population modules in both sole cropping and intercropping populations of soybean and wheat were analyzed. Results using nutrient levels of ½- or ¼-strength Hoagland solution indicated that soybean/wheat intercropping population modules significantly increased at low planting densities (D20 and D26) and significantly decreased at high planting densities (D32 and D60). Therefore, as planting density increased, the modules of both intercropping populations initially increased before decreasing. Similarly, positive interaction initially strengthened before weakening. Moreover, at an intermediate planting density, the population modules reached their maxima, and the positive interaction was the strongest. Under the same planting density, ¼-strength Hoagland solution recorded better growth for the soybean/wheat intercropping population modules compared to results using the ½-strength Hoagland solution. These findings indicated that low nutrient level can increase the positive interaction of intercropping populations at a given planting density, and that environmental nutrient level and population planting densities constrain the positive interaction between soybean and wheat populations in the intercropping system. This study highlights issues that need to be addressed when constructing intercropping populations.