Microplastics (MPs) are important carriers of various toxic metals and can alter their toxicity pattern in agricultural soil, leading to combined pollution, therefore posing new challenges to soil pollution management and environmental risk assessment. In this study, we observed the internalization of MPs in plants and conducted incubation experiments to evaluated the effects of arsenate (As(V)) alone and in combination with polystyrene (PS) MPs on wheat seedlings (Triticum aestivum L.). Under As(V) alone and combined with PS-MP exposure, dosedependent toxicity in terms of root and stem elongation and biomass accumulation was observed. Compared with As(V) alone, the presence of PS-MPs reduced the accumulation of As in wheat roots by 11.43-58.91%, but PSMPs intensified the transport of As to the aboveground parts of wheat, increasing As accumulation in wheat stems by 27.77-1011.54%. This causes more serious mechanical damage and oxidative stress to plant cells, increasing the accumulation of reactive oxygen species and lipid peroxidation in wheat roots and upregulating the activities of antioxidant enzymes such as superoxide dismutase (SOD) and peroxidase (POD). In addition, the co-exposure of As(V) and PS-MPs disrupts the photosynthetic system of wheat leaves and the secretion activities of roots. Therefore, the combination of As(V) and PS-MPs caused greater damage to wheat growth. Our findings contribute to a more comprehensive assessment of the combined toxicity of MPs and heavy metal to crops.

Heavy metals in soil can inflict direct damage on plants growing within it, adversely affecting their growth height, root development, leaf area, and other physiological traits. To counteract the toxic impacts of heavy metals on plant growth and development, plants mitigate heavy metal stress through mechanisms such as metal chelation, vacuolar compartmentalization, regulation of transporters, and enhancement of antioxidant functions. WRKY transcription factors (TFs) play a crucial role in plant growth and development as well as in responses to both biotic and abiotic stresses; notably, heavy metal stress is classified as an abiotic stressor. An increasing number of studies have highlighted the significant role of WRKY proteins in regulating heavy metal stress across various levels. Upon the entry of heavy metal ions into plant root cells, the production of reactive oxygen species (ROS) is triggered, leading to the phosphorylation and activation of WRKY TFs through MAPK cascade signaling. Activated WRKY TFs then modulate various physiological processes by upregulating or downregulating the expression of downstream genes to confer heavy metal tolerance to plants. This review provides an overview of the research advancements regarding WRKY TFs in regulating heavy metal ion stress-including cadmium (Cd), arsenic (As), copper (Cu)-and aluminum (Al) toxicity.

Chromated copper arsenate (CCA) is a wood preservative containing Cr, Cu, and As and leaching of these heavy metals into agricultural fields raises concern about food safety. The heavy metals enter the plants due to hydrophilic nature and prevalent mobility by damaging the photosynthetic process and hindering metabolism of plants. Phytoremediation is one of the constructive methods employed in mitigation of toxic metals from the soil. Nevertheless, only limited studies have been conducted on the effect of heavy metals and chelating agents on biochemical parameters in tree species. Overall, the present study advocates the possible effects of CCA components, EDTA and DTPA, on total carbohydrates, protein, and chlorophyll content of Acacia auriculiformis and Casuarina equisetifolia seedlings. Experiments on the effect of CCA and chelating agents on biochemical parameters of seedlings were conducted in potting medium. The plastic pots transplanted with 1-month-old seedlings of Acacia auriculiformis and Casuarina equisetifolia were supplied with sufficient air-dried soil and compost followed by treatment of six different concentrations (250-2500 mg kg(-1) soil) of CCA. Simultaneously, in a separate set of experiments, pots with planting media were supplied with CCA (1000 mg kg(-1) soil) followed by treatment of four different concentrations of EDTA and DTPA (0.1-1.5 mu M kg(-1)). The leaves of 6-month-old seedlings of both tree species exposed to different concentrations of CCA and chelating agents were harvested and the amount of total carbohydrates, protein, and chlorophyll content was estimated by spectrophotometric methods. The results of different treatments were compared with the control. Results of the study showed significant decrease (p <= 0.05) in the amount of total carbohydrates, proteins, and chlorophyll content with an increase in concentrations of CCA (750-2500 mg kg(-1)) in the seedlings of A. auriculiformis and C. equisetifolia. Similarly, the seedlings of both tree species treated with 1.5 mu M kg(-1) each of EDTA and DTPA showed significantly (p <= 0.05) increased total carbohydrate, proteins, and chlorophyll content. The studies conclude that the CCA components affect the total carbohydrate, protein, and chlorophyll content of the A. auriculiformis and C. equisetifolia seedlings. However, moderate to higher concentrations of EDTA and DTPA were effective in ameliorating CCA toxicity.