Search Results (8)

Cadmium (Cd) is a major environmental pollutant due to its high mobility and persistence in soils, facilitating entry into the food chain and threatening ecosystems and human health. However, the mechanisms that enable Salix species, well adapted for Cd remediation, to both tolerate and accumulate Cd remain elusive. Here, two Salix genotypes with contrasting Cd tolerance were examined under control and Cd stress using integrated physiological, transcriptomic, and metabolomic analyses of roots and leaves. The Cd-tolerant genotype (Salix suchowensis P294) maintained biomass under Cd stress, whereas the Cd-sensitive genotype (Salix sinopurpurea × Salix integra P646) showed a ~17% reduction. P294 accumulated more Cd in its stems (132.76 mg kg⁻¹) and leaves (122.25 mg kg⁻¹) than P646 (93.54 and 56.24 mg kg⁻¹). Transcriptomics responses were stronger in roots, with 896 DEGs in P294 and 462 in P646, enriched in nitrogen metabolism, phenylpropanoid biosynthesis, and metal transport, whereas only 167 and 176 DEGs were detected in leaves for P294 and P646, respectively. Metabolomics revealed more altered metabolites in roots (125 in P294, 89 in P646), mainly organic acids, amino acids, and flavonoids, compared with leaves (46 and 66). RT-qPCR validated the root-specific upregulation of key detoxification and transport genes (ABCA7, PRX72, GSTU1, GSTU4, ZIP1). These results reveal a root-centered regulatory network underlying Cd accumulation and tolerance, integrating detoxification, redox homeostasis, and structural reinforcement, as well as providing valuable targets for genetic improvement of phytoremediation efficiency. Full article

Lead (Pb) is a widespread environmental pollutant that severely threatens plant growth and development. While the mechanisms of Pb uptake and accumulation have been extensively studied in herbaceous plants, the glutathione (GSH)-mediated biochemical responses in woody species remain largely unexplored. This knowledge gap limits our understanding of the detoxification strategies of perennial plants with high phytoremediation potential. In this study, two Salix integra clones (P336 and P646) with contrasting Pb tolerance were used to investigate the temporal regulation of GSH metabolism under Pb stress. P336 displayed both early and sustained increases in cysteine (Cys), GSH, ascorbic acid (AsA), phytochelatins (PCs), and the activities of γ-ECS and APX, conferring stronger antioxidant and detoxification capacity than P646. Notably, glutathione reductase (GR) activity remained unchanged in both clones, indicating that GSH homeostasis was maintained mainly through de novo synthesis rather than GR-mediated recycling. These findings demonstrate that Pb tolerance in P336 is achieved through γ-ECS–driven de novo GSH biosynthesis, which sustains both the AsA–GSH cycle and PC synthesis for efficient ROS detoxification and Pb sequestration. By providing the first detailed evidence of GSH-centered detoxification dynamics in a woody phytoremediant, this study advances our mechanistic understanding of Pb tolerance in S. integra and highlights its application potential in the phytoremediation of Pb-contaminated environments. Full article

Willows are suitable candidates for phytoremediation projects. A pot experiment was conducted to evaluate the potential of using Salix unrooted cuttings for the phytoremediation of lead/zinc (Pb/Zn) and copper (Cu) mine tailings. Cuttings of 14 Salix clones were directly rooted into pots containing mine tailings. The 14 clones showed different levels of tolerance to tailing treatments. A total of 71.40% and 85.70% of the S. jiangsuensis ‘172’ cuttings either grown in Pb/Zn or Cu tailings survived, respectively. However, the other clones had lower survival rates, and the values were no more than 40%. Usually, all clones produce less biomass in an extremely contaminated environment. Clonal variation in biomass yield was observed in this research. The surviving clones, such as S. integra ‘WSH’, S. matsudana ‘14’, S. chaenomeloides ‘3’, S. chaenomeloides ‘4’, and S. chaenomeloides ‘5’ (Pb/Zn tailing), S. integra ‘HY’, S. integra ‘WSH’, S. matsudana ‘14’, S. matsudana ‘19’, and S. matsudana ‘34’ (Cu tailing) produced relatively more biomass in this study. In general, all the clones presented lower bioconcentration factor values for the tailings of heavy metals. In principle, all clones could easily take up and translocate Zn and Cd from the tailings to aboveground parts, especially S. integra. All clones exhibited a huge variation in their heavy metal accumulation capacity. As stated above, the direct utilization of cuttings for phytoremediation is a viable option. S. jiangsuensis ‘172’ had a high tolerance capacity and would be a recommended candidate for future phytoremediation projects in soils containing tailings with an extremely high concentration of heavy metals. These results provide crucial information about willow growth and metal accumulation capacity in extremely adverse environments. Full article

The NAC (NAM-ATAF1/2-CUC) transcription factor family is one of the largest plant-specific transcription factor families, playing an important role in plant growth and development and abiotic stress response. As a short-rotation woody plant, Salix integra (S. integra) has high lead (Pb) phytoremediation potential. To understand the role of NAC in S. integra Pb tolerance, 53 SiNAC transcripts were identified using third-generation and next-generation transcriptomic data from S. integra exposed to Pb stress, and a phylogenetic analysis revealed 11 subfamilies. A sequence alignment showed that multiple subfamilies represented by TIP and ATAF had a gene that produced more than one transcript under Pb stress, and different transcripts had different responses to Pb. By analyzing the expression profiles of SiNACs at 9 Pb stress time points, 41 of 53 SiNACs were found to be significantly responsive to Pb. Short time-series expression miner (STEM) analysis revealed that 41 SiNACs had two significant Pb positive response patterns (early and late), both containing 10 SiNACs. The SiNACs with the most significant Pb response were mainly from the ATAF and NAP subfamilies. Therefore, 4 and 3 SiNACs from the ATAF and NAP subfamilies, respectively, were selected as candidate Pb-responsive SiNACs for further structural and functional analysis. The RT-qPCR results of 7 transcripts also confirmed the different Pb response patterns of the ATAF and NAP subfamilies. SiNAC004 and SiNAC120, which were randomly selected from two subfamilies, were confirmed to be nuclear localization proteins by subcellular localization experiments. Functional prediction analysis of the associated transcripts of seven candidate SiNACs showed that the target pathways of ATAF subfamily SiNACs were “sulfur metabolism” and “glutathione metabolism”, and the target pathways of NAP subfamily SiNACs were “ribosome” and “phenylpropanoid biosynthesis”. This study not only identified two NAC subfamilies with different Pb response patterns but also identified Pb-responsive SiNACs that could provide a basis for subsequent gene function verification. Full article

To establish a short rotation coppice (SRC) system in the temperate region of East Asia, planting was conducted for cuttings from seven species, including Salix eriocarpa, S. gilgiana, S. gracilistyla, S. integra, S. sachalinensis, S. serissaefolia, and S. subfragilis, with wide distribution in eastern Japan. During cultivation, cheap compost derived from swine manure and containing high concentrations of various nutrients was added. Three treatment groups, including control, low manure (5 Mg ha⁻¹), and high manure (10 Mg ha⁻¹) treatments, were established, and seven willows were grown for two complete growing seasons to obtain the clone density of 10,000 cuttings ha⁻¹. The manure treatments accelerated the growth of all the willow species after two growing seasons. The averages of annual biomass production of seven willows grown under the control, low manure, and high manure treatments were 0.2 Mg ha⁻¹yr⁻¹, 5.3 Mg ha⁻¹yr⁻¹, and 8.5 Mg ha⁻¹yr⁻¹, respectively. By comparing with the biomasses of seven willows, the largest annual biomass production rates of 14.1 and 13.7 Mg ha⁻¹yr⁻¹ were observed in the high manure treatments of S. sachalinensis and S. subfragilis, respectively. For two species under the high manure treatment, S. sachalinensis had the thickest shoots, and S. subfragilis had the tallest shoots. These growth characteristics of S. sachalinensis and S. subfragilis originate from their high biomass production. Overall, these results suggest that S. sachalinensis and S. subfragilis are potentially feasible candidates for the SRC system in temperate regions of East Asia. Full article

The vegetation changes in the abandoned rice fields with different abandonment histories were analyzed across the country of South Korea. The successional process was confirmed by changes in vegetation profiles and species composition. The vegetation profile showed the process of starting with grassland, passing through the shrub stage, and turning into a tree-dominated forest. DCA ordination based on vegetation data showed that the process began with grasslands consisting of Persicaria thunbergii, Juncus effusus var. decipiens, Phalaris arundinacea, etc., then partially went through shrubland stages consisting of Salix gracilistyla, S. integra, young Salix koreensis, etc., and ultimately changed to a Salix koreensis dominated forest. In order to study the relationship between the succession process of the abandoned rice paddies and riparian vegetation, information on riparian vegetation was collected in the same watershed as the abandoned rice paddies investigated. Riparian vegetation tended to be distributed in the order of grasslands consisting of Phragmites japonica, Miscanthus sacchariflorus, P. arundinacea, etc., shrubland dominated by Salix gracilistyla, S. integra, etc., and a S. koreensis community dominated forest by reflecting the flooding regime as far away from the waterway. The result of stand ordination based on the riparian vegetation data also reflected the trend. From this result, we confirmed that the temporal sequence of the vegetation change that occurred in the abandoned rice fields resembled the spatial distribution of the riparian vegetation. Consequently, succession of the abandoned rice fields restored the riparian forest, which has almost disappeared in Korea and other Asian countries that use rice as their staple food. Full article

Flooding can adversely worsen metal-contaminated soil and influence phytoremediation efficiency; thus, it is crucial to explore the eco-physiological responses of plants to the combined stress of metals and flooding. Here, the plant growth, photosynthesis, and nutrient composition in the arbor willow (Salix jiangsuensis ‘J172’) and shrub willow (Salix integra ‘Yizhibi’) were studied using a pot experiment with Cu-contaminated soil (239.5 mg$·$kg⁻¹) under flooded versus non-flooded conditions. S. integra showed a larger bioconcentration factor (BCF) than S. jiangsuensis in both treatments. Flooding markedly decreased the BCFs while obviously increasing the translocation factor in the two willows (p$<$ 0.05). Flooding enhanced the leaf C:P and N:P ratios while significantly decreased root C:P and N:P ratios, compared to the non-flooded condition. The shrub willow exhibited better tolerance to flooding, with little alteration in biomass and photosynthetic rate, and showed greater potential Cu accumulation capacity, even though its total biomass was significantly lower than that of the arbor willow. Our study also helps further understanding of nutrient balance and stoichiometry of willows in response to flooding and Cu contamination, promoting the management of Cu-contaminated flooded soils. Full article

Background and Objectives: Salix integra Thunb., a fast-growing woody species, has been used in phytoremediation in recent years. It has the potential to accumulate high amounts of lead (Pb) in its growth, however, its effects on soil microbial community structure and function during its phytoextraction processes are not well understood, especially at different pollution levels. Materials and Methods: In our study, we set unplanted and planted Salix integra in areas with four levels of Pb treatments (0, 500, 1000, and 1500 mg/kg). After six months of planting, the rhizospheric soil, bulk soil, and unplanted soil were collected. Soil properties and microbes participating in nitrogen and phosphorus cycling were measured, following standard methods. Microbial metabolic functions were assessed using a Biolog-ECO microplate. Results: The bacteria (nitrogen-fixing bacteria, ammonifying bacteria, inorganic phosphorus-solubilizing bacteria, and nitrosobacteria) all increased in the 500 mg/kg treatment and decreased in the 1500 mg/kg treatment compared with the 0 mg/kg treatment, especially in rhizospheric soil. The microbial metabolisms decreased along with the increase of Pb levels, with the exception of the rhizospheric soil with a 500 mg/kg treatment. The metabolic patterns were relative to the pollution levels. The utilization of carbohydrates was decreased, and of amino acids or fatty acids was increased, in the 500 mg/kg treatment, while the opposite occurred in the 1500 mg/kg treatment. The values of soil properties, microbial quantities, and metabolic activities were higher in rhizospheric than bulk soil, while the differences between bulk and unplanted soil were different among the different Pb treatments. The soil properties had little effect on the microbial quantities and metabolic activities. Conclusions: S. integra planting and Pb levels had an interactive effect on the microbial community. In general, S. integra planting promoted microbial quantities and metabolic activity in rhizospheric soil. Lower Pb pollution increased microbial quantities and promoted the utilization of amino acids or fatty acids, while higher Pb concentrations decreased microbial quantities and metabolic activities, and promoted the utilization of carbohydrates. Full article