Heavy metal contamination is a global problem for ecosystems and human health. Remediation of contaminated soils has received much attention in the last decade. Aided mitigation of heavy metal phytotoxicity by arbuscular mycorrhizal fungi (AMF) is a cost-effective and environmentally friendly strategy. This study was carried out to investigate the mitigation effect of AMF inoculation on heavy metal toxicity in Medicago truncatula under soil cadmium stress. Therefore, a pot experiment was designed to evaluate the growth, chlorophyll fluorescence, Cd uptake and distribution, malondialdehyde (MDA) content, root soil physicochemical properties, and metabolite profile analysis of M. truncatula with/without AMF inoculation in Cd (20 mg/Kg)-contaminated soil. The results showed that inoculating AMF under Cd stress might enhance photosynthetic efficiency, increase plant biomass, decrease Cd and MDA content, and improve soil physicochemical properties in M. truncatula. Non-targeted metabolite analysis revealed that inoculation with AMF under Cd stress significantly upregulated the production of various amino acids in inter-root metabolism and increase organic acid and phytohormone synthesis. This study provides information on the physiological responses of mycorrhizal plants to heavy metal stress, which could help provide deeper insight into the mechanisms of heavy metal remediation by AMF.

Although more attention has been paid to microplastics (MPs) pollution in environment, research on the synthetic influence of microplastic and heavy metals remains limited. To help fill this information gap, we investigated the adsorption behavior of virgin polyvinyl chloride microplastics (PVCMPs) (≤450 µm white spherical powder) on cadmium (II). The effects on seed germination, seedling growth, photosynthetic system, oxidative stress indicators of lettuce, and changes in Cd bioavailability were evaluated under Cd²⁺ (25 μmol/L), PVCMPs (200 mg/L), and PVCMP-Cd combined (200 mg/L + 25 μmol/L) exposures in hydroponic system. The results demonstrated that the PVCMPs effectively adsorbed Cd ions, which validated by the pseudo-second-order kinetic and the Langmuir isotherm models, indicating the sorption of Cd²⁺ on the PVCMPs was primary chemisorption and approximates monomolecular layer sorption. Compared to MPs, Cd significantly inhibits plant seed germination and seedling growth and development. However, Surprising improvement in seed germination under PVCMPs-Cd exposure was observed. Moreover, Cd²⁺ and MPs alone or combined stress caused oxidative stress with reactive oxygen species (ROS) including H₂O₂, O^2- and Malondialdehyde (MDA) accumulation in plants, and substantially damaged to photosynthesis. With the addition of PVCMPs, the content of Cd in the leaves significantly (P<0.01) decreased by 1.76-fold, and the translocation factor and Cd²⁺removal rate in the water substantially (P<0.01) decreased by 6.73-fold and 1.67-fold, respectively in contrast to Cd²⁺ stress alone. Therefore, it is concluded the PVCMP was capable of reducing Cd contents in leaves, alleviating Cd toxicity in lettuce. Notably, this study provides a scientific foundation and reference for comprehending the toxicological interactions between microplastics and heavy metals in the environment.

Nuclides pollution and its biological effects are of great concern, especially for bryophytes during their terrestrial adaptation. Understanding PSII activity and electron transport response is vital for comprehending moss abiotic stress reactions. However, little is known about the photosynthetic performance of moss under nuclide treatment. Therefore, this study aimed to evaluate the chlorophyll fluorescence of Racomitrium japonicum L. The moss was subjected to Sr²⁺ solutions at concentrations of 5, 50, and 500 mg/L to evaluate chlorophyll a fluorescence using the OJIP test. Moderate and high Sr²⁺ stress led to inner cell membrane dissolution and reduced chlorophyll content, indicating impaired light energy absorption. At 5 mg/L Sr²⁺, fluorescence kinetics showed increased light energy capture, energy dissipation, and total photosynthetic driving force, thus stimulating transient photosynthetic activity of PSII and improving PSI reduction. Linear electron transfer and PSII stability significantly decreased under moderate and high Sr²⁺ stress, indicating potential photosynthetic center damage. Cyclic electron transfer (CEF) alleviated photosynthetic stress at 5 mg/L Sr²⁺. Thus, low Sr²⁺ levels stimulated CEF, adjusting energy flux and partitioning to protect the photosynthetic apparatus. Nevertheless, significant damage occurred due to inefficient protection under high Sr²⁺ stress.

Attention is increasingly being paid to the contamination of soil by the radioactive element uranium (U). Phytoremediation of contaminated soil by economically advantageous and environment-protective plants shows considerable potential for addressing this problem. Populus cathayana is a species with high heavy-metal tolerance, economic value, and notable potential for phytoremediation. Plant-sex-related differences can lead to differences in vegetative growth and tolerance to various stressors. As such, in this study, we designed a pot experiment to analyze the responses of male and female trees of P. cathayana to 50 mg kg⁻¹ U stress in contaminated soil for 3 months. We studied the U uptake and distribution, photosynthesis, chlorophyll fluorescence, active oxygen species, and antioxidant enzymes of P. cathayana. The results showed that the photosynthetic activity and chlorophyll fluorescence of male and female trees were similar, and U stress mainly affected the nonstomatal factors and photosystem II during photosynthesis. Regarding the physiological and biochemical processes, male and female trees showed different defense strategies: male trees had higher peroxidase (POD), H₂O₂, and soluble sugars, but lower malondialdehyde (MDA), superoxide dismutase (SOD), and soluble proteins. Under U stress, the active oxygen produced by male trees could be cleared by antioxidant enzymes, preventing damage to the cell membrane. Male trees accumulated a higher U concentration in their roots than female trees, whereas the transportation of U from roots to leaves in male trees was lower than that in female trees. Therefore, our results suggested that male trees have a higher tolerance capacity and greater ability to remediate U-polluted soil than female trees. Future phytoremediation studies should consider the differences between plant sexes in the tolerance to U-contaminated land.