Pb Stress Research Articles

Elucidating the protective role of manganese seed priming in mitigating lead-induced oxidative stress: enhancements in growth, grain yield, and antioxidant activities of wheat.

Lead (Pb) is known to be extremely toxic to plants and awfully affects growth and productivity by interacting with morphological, biochemical, and physiological processes. Micronutrients are considered to reduce ion toxicity and modify various physiological processes involved in oxidative stress tolerance in plants. Hence, the limited literature about the application of micronutrients, particularly manganese (Mn), under lead stress thus demands more investigations. To sort out the role of priming treatments of Mn (1.0 and 0.1mg/L) in lead stress (200mg/kg) induced oxidative stress tolerance in wheat cultivars (Anaj-17 and Akbar-19), current experiment was designed. The experiment was arranged with completely randomized design (CRD) with three replicates. The results explored the positive role of Mn priming in strengthening the antioxidant system with increased activities of antioxidants under Pb stress. Mn priming level (0.1mg/L) significantly increased the germination percentage, germination percentage, growth traits, grain yield per plant, shoot P, shoot Ca2+, and shoot K+ while decreasing the MDA and H2O2 levels, of Anaj-17 and Akbar-19 under Pb stress (200mg/kg). Seed priming levels of Mn further upgraded the antioxidant enzymatic activities and organic osmolytes such as proline, total phenolics, flavonoids, total soluble sugars, and glycine betaine, under Pb stress. Conclusively, the 0.1mg/L level of Mn priming and Akbar-19 cultivar has proven superior in lead detoxification under Pb-induced oxidative stress. Furthermore, the outcomes revealed more accumulation of Pb in the roots of wheat than in the shoots of both wheat cultivars and emphasized the use of lower Mn levels of 0.1mg/L as the best strategy in alleviating the toxic impacts of lead in wheat. However, the conduct of large field trials is a necessity of current scenario to study the molecular aspects and associated genes contributing Pb stress tolerance with priming application of Mn and other micronutrients.

Biochar co-compost increases the productivity of Brassica napus by improving antioxidant activities and soil health and reducing lead uptake

Lead (Pb) is a serious toxic metal without any beneficial role in the biological system. Biochar (BC) has emerged as an excellent soil amendment to mitigate Pb toxicity. The impact of BC co-compost (BCC) in mitigating the toxic impacts of Pb has not been studied yet. Therefore, this study aimed to evaluate the potential of BC and BCC in improving the growth, physiological, and biochemical traits of Brassica napus and soil properties and reducing health risks (HR). The study was comprised of different Pb concentrations (control and 100 mg kg-1) and organic amendments (control, BC, compost, and BCC). The results indicated that Pb stress reduced the growth, photosynthetic pigments, seed yield, and oil contents by increasing hydrogen peroxide (H2O2) production and Pb uptake and accumulation in plant tissues and decreasing photosynthetic pigment and nutrient availability. The application of BCC alleviated the adverse impacts of Pb and improved seed production (40.24%) and oil yield (11.06%) by increasing chlorophyll a (43.18%) and chlorophyll b (25.58%) synthesis, relative water content (23.89%), total soluble protein (TSP: 23.14%), free amino acids (FAA: 26.47%), proline (30.98%), APX (40.90%), CAT (32.79%), POD (24.93%), and SOD (33.30%) activity. Biochar co-compost-mediated increase in seed and oil yield was also linked with a reduced accumulation of Pb in plant parts and soil Pb availability and improved the soil-available phosphorus, potassium, total nitrogen, soil organic carbon (SOC), and microbial biomass carbon (MBC). Furthermore, BCC also reduced the bioaccumulation concentration, daily metal intake, hazard index, and target hazard quotient. In conclusion, application of BCC can increase the growth, yield, and oil contents of Brassica napus by improving the physiological and biochemical traits and soil properties and reducing the Pb uptake.

Deciphering the Driving Mechanism and Regulatory Strategies of Antibiotic Resistance Genes Transmission in Lead-Contaminated Soil Microbial Communities by Multiple Remediation Methods

Pb-contaminated soil poses inherent risks for the spread of antibiotic resistance genes (ARGs). However, few reports have investigated the distribution of lead resistance genes (LRGs), particularly their role in ARGs dynamics during Pb-contaminated soil remediation. This study explored the mechanisms driving ARGs variation under different remediation strategies. The results indicated that an increase in the total abundance of ARGs after applying montmorillonite (Imvite), the composite remediation agents of MgO and Ca(H2PO4)2 (MgO-Ca(H2PO4)2), and the composite remediation agents of montmorillonite, MgO, and Ca(H2PO4)2 (Imvite-MgO-Ca(H2PO4)2). Bioelectrochemical systems (BES) effectively reduced ARGs abundance, and when combined with Imvite-MgO-Ca(H2PO4)2, lowered the risk of ARGs proliferation linked to antibiotic deactivation. Changes in Pb concentration and pH reshaped microbial communities, impacting both LRGs and ARGs. To reduce the risk of ARGs proliferation and transmission during, various control strategies, such as modifying Pb stress, adjusting pH, and manipulating microbial community structure, have been proposed. The study provided theoretical foundation and practical strategies for controlling ARGs dissemination during the remediation of heavy metal-contaminated soil.

Deciphering the mechanisms, signaling, and applications of newly isolated Cladosporium crousii SHF to alleviate the negative effects of Pb stress in tomato plants

Deciphering the mechanisms, signaling, and applications of newly isolated Cladosporium crousii SHF to alleviate the negative effects of Pb stress in tomato plants

Multi-Omics Analysis Reveals the Mechanism by Which RpACBP3 Overexpression Contributes to the Response of Robinia pseudoacacia to Pb Stress.

Acyl-CoA-binding protein (ACBP) genes have been implicated in lead enrichment and translocation in plants; however, the mechanisms by which these genes contribute to the response to heavy metal stress in various taxa have not been determined. In this study, the molecular mechanisms underlying the response of Robinia pseudoacacia, an economically important deciduous tree, to Pb stress were examined using transcriptomic and metabolomic analyses. RpACBP3 overexpression increased Pb enrichment, translocation, and tolerance. After Pb stress for 3 days, 1125 differentially expressed genes (DEGs) and 485 differentially accumulated metabolites (DAMs) were identified between wild-type and RpACBP3-overexpressing R. pseudoacacia strains; after Pb stress for 45 days, 1746 DEGs and 341 DAMs were identified. Joint omics analyses showed that the DEGs and DAMs were co-enriched in α-linoleic acid metabolism and flavonoid biosynthesis pathways. In particular, DEGs and DAMs involved in α-linoleic acid metabolism and flavonoid biosynthesis were up- and down-regulated, respectively. Moreover, RpACBP3 overexpression enhanced the ability to scavenge reactive oxygen species and repair cell membranes under stress by regulating LOX gene expression and increasing the phosphatidylcholine content, thereby improving the tolerance to Pb stress. These findings lay a theoretical foundation for the future application of RpACBP3 genes in plant germplasm resource creation and phytoremediation of Pb contaminated soil in which R. pseudoacacia grow.

Bacillus altitudinis Mediated Lead Bioremediation for Enhanced Growth of Rice Seedlings.

Lead (Pb) is a hazardous environmental pollutant that threatens soil health, water quality, and agricultural productivity. Plant growth-promoting rhizobacteria (PGPRs) mediated bioremediation is considered as an eco-friendly approach for agro-environmental sustainability. This study investigated the Pb bioremediation potential of Bacillus altitudinis (IHBT-705). The results revealed that IHBT-705 strain tolerated upto 15mM of Pb, possessed 96% Pb bioaccumulation efficiency, and also maintained its plant growth-promoting (PGP) traits under Pb stress. Furthermore, IHBT-705 strain treated with 15mM Pb solution (IHBT-W) and soil containing 15mM Pb treated with IHBT-705 inoculum (IHBT-S) ameliorated the detrimental effects of Pb stress. Both IHBT-W and IHBT-S treatment significantly improved the shoot length, root length, total roots, chlorophyll content, and antioxidants enzyme activity of the rice seedlings as compared to the seedlings treated with 15mM Pb solution (Pb-W) and soil containing 15mM Pb (Pb-S). Also, IHBT-W and IHBT-S treatment decreased the Pb content in the rice plant by 97 and 96% over their respective Pb-W and Pb-S plants. Overall, our research underscores the remarkable Pb bioremediation potential of IHBT-705, offering a promising avenue for dual function, i.e. improving soil health and promoting plant growth under Pb contamination.

Adaptive mechanisms of wheat cultivars to lead toxicity through enhanced oxidative defense, ionomic redistribution, and anatomical modifications

Lead (Pb) contamination is a critical environmental issue that poses a substantial threat to agricultural sustainability and crop productivity, particularly for staple crops like wheat (Triticum aestivum L.). This study investigates the differential physiological, biochemical, and anatomical responses of two wheat cultivars, SKD-1 and Borlaug-16, under Pb stress (100 mg/kg Pb for 21 days). Borlaug-16 displayed a notable tolerance to Pb toxicity, evidenced by a significant increase in total biomass, including a 41.22% rise in shoot turgid weight and a 23.37% increase in root turgid weight, alongside a 57.72% enhancement in root cortex thickness. This cultivar also showed increased antioxidant enzyme activities, such as catalase and peroxidase, and a better ionomic balance, maintaining higher levels of essential minerals like Ca in leaf tissues while effectively accumulating Pb and other trace elements in roots. In contrast, SKD-1 suffered from a more substantial reduction in essential minerals and weaker anatomical and biochemical defenses. The study's novelty lies in providing an integrated approach to understanding wheat cultivar-specific adaptations to Pb stress, suggesting Borlaug-16 as a promising candidate for cultivation in Pb-contaminated soils. These findings underscore the importance of developing Pb-tolerant cultivars to ensure sustainable wheat production in polluted environments.

Multi-functional PGPR Serratia liquefaciens confers enhanced resistance to lead stress and bacterial blight in soybean (Glycine max L.)

Lead toxicity and bacterial blight disease caused by Pseudomonas savastanoi pv. glycinea have destructive impacts on soybean growth and productivity. Plant growth-promoting rhizobacteria have been used as an eco-friendly approach for augmenting crop growth and stress resistance. The current study investigated the efficacy of Serratia liquefaciens ZM6 strain in enhancing soybean resistance to lead (Pb) stress and bacterial blight. Two pot experiments were performed. In the first pot experiment, soybean plants were inoculated with S. liquefaciens ZM6 and grown under variable Pb stress levels (0, 200 and 400µM of Pb(NO3)2). In the second experiment, S. liquefaciens-inoculated soybean plants were infected with P. savastanoi pv. glycinea, and disease severity was assessed two weeks post infection. The results revealed that S. liquefaciens strain resisted Pb stress up to 400µM Pb(NO3)2 and exhibited the highest levels of solubilized phosphate, solubilized zinc, siderophore, indole acetic acid, exopolysaccharide, trehalose and antioxidant enzymes at 400µM Pb compared to the other treatments. Moreover, Pb stress (200 and 400µM) significantly decreased the growth, yield, nutrient uptake, gas exchange, and contents of chlorophyll, soluble proteins, sugars, and phenolics of soybean plants. Pb stress also induced the levels of proline, glycine betaine, Pb, oxidative stress markers, antioxidant enzymes, ascorbate, glutathione and expression of stress-responsive genes (CAT, APX, POD, Fe-SOD, CHS7, CHI1A, PAL, IFS2, P5CS and WRKY54) in soybean plants. On the other hand, S. liquefaciens application markedly boosted the growth, yield and levels of nutrients, gas-exchange, chlorophyll, osmolytes, antioxidant enzymes and expression of stress-tolerant genes of Pb-stressed soybean plants. The bacterial inoculation significantly diminished oxidative stress indicators and Pb content in stressed plants. Inoculation of soybean plants with S. liquefaciens also caused significant reductions in blight disease symptoms in P. savastanoi pv. glycinea-infected plants, indicating the efficiency of this strain in controlling harmful blight disease. Overall, this study demonstrated S. liquefaciens ZM6 effectiveness in enhancing soybean resistance to Pb stress and bacterial blight.

WITHDRAWN: Enhancing Maize Growth Under Drought and Lead Stress with Deashed Biochar and Growth-Promoting Rhizobacteria

The agricultural sector faces significant challenges due to water scarcity and increasing lead (Pb) contamination, adversely affecting crop productivity by generating reactive oxygen species (ROS) during Pb stress and drought. Biochar and plant growth-promoting rhizobacteria (PGPR) are emerging as effective tools to manage oxidative stress, yet the combined use of deashed biochar (BC) and PGPR remains underexplored. This study aimed to investigate the synergistic effects of BC and Agrobacterium fabrum on maize growth and biochemical attributes. Two levels of BC (control and 0.5%) were applied with and without A. fabrum under no Pb stress (0 mg Pb/kg soil) and 400 mg Pb/kg soil stress conditions. Additionally, seeds inoculated with A. fabrum were subjected to no drought stress (65% field capacity w/v) and drought stress (40% field capacity w/v). Conducted with three replicates in a randomized design within controlled greenhouse conditions, the study demonstrated that BC+A. fabrum treatment significantly improved maize germination (53.33%), shoot length (69.32%), root length (11.76%), and total soluble protein content (32.36%) under 400 mg Pb/kg soil stress compared to controls. Furthermore, BC+A. fabrum effectively mitigated drought stress, enhancing chlorophyll a (55.02%), chlorophyll b (50.61%), and total chlorophyll (53.37%) levels compared to controls. Analysis of key antioxidants (peroxidase, superoxide dismutase, catalase, and ascorbate peroxidase) revealed BC+A. fabrum ability to modulate antioxidant defenses in maize, underscoring its potential as a sustainable strategy to enhance maize growth resilience under combined Pb and drought stress conditions. Future studies should explore the long-term effects and field applicability of BC+A. fabrum treatments to optimize agricultural sustainability and productivity in Pb-contaminated and drought-prone environments.

Responses to exogenous elicitor treatment in lead-stressed Oryza sativa L.

Heavy metal toxicity adversely affects plants by changing physiological, biochemical, and molecular mechanisms. Lead (Pb) is one of the most common heavy metal pollutants. Hence this study investigated changes caused by exogenous methyl jasmonate (MeJA; 20 and 100 µM) and salicylic acid (SA; 2 and 20 mM) elicitors in local Karacadağ rice exposed to Pb stress (0, 100, and 400 ppm). The effects of elicitors on photosynthetic pigment content (chlorophyll a, chlorophyll b, and total carotenoid), proline, malondialdehyde (MDA), total phenolic and flavonoid, Pb, and total protein contents in stressed plants were evaluated. All parameters studied increased and decreased at varying rates in the treatment groups compared to the Pb-free group (control), indicating that rice plants were affected by Pb stress. The elicitors (MeJA, SA, and MeJA + SA) were applied by foliar spraying. The elicitor treatments increased photosynthetic pigment content, total protein, proline, total flavonoid, and phenolic contents depending on the elicitor type and concentration. MDA and Pb contents, increasing with Pb toxicity, decreased with elicitor treatments, and the stress degree was reduced. When the elicitors were compared, SA was more effective than MeJA in total flavonoid content at 400 ppm Pb toxicity. However, MeJA was more effective in photosynthetic pigment contents, MDA, total protein, Pb, total phenolic, and proline contents. The best results for all parameters examined in rice plants exposed to Pb toxicity were obtained from the 400 ppm Pb + 2 mM SA + 20 µM MeJA treatment group. In conclusion, this study showed that the combined application of MeJA + SA alleviated the harmful effects of Pb by reducing MDA and increasing photosynthetic pigments, total protein, proline, and secondary metabolites, especially at high Pb concentrations. Consequently, this study demonstrated that the combined use of MeJA and SA in rice plants eliminated the negative effects of stress quite effectively, even at high Pb concentrations. Therefore, future studies should focus on the synergistic application of different elicitors to better understand the effects of heavy metal toxicity on plant growth and development.

Lead-induced changes in plant cell ultrastructure: an overview.

Lead (Pb) is one of the most harmful toxic metals and causes severe damage to plants even at low concentrations. Pb inhibits plant development, reduces photosynthesis rates, and causes metabolic disfunctions. Plant cells display these alterations in the form of abnormal morphological modifications resulting from ultrastructural changes in the cell wall, plasma membrane, chloroplast, endoplasmic reticulum, mitochondria, and nuclei. Depending on plant tolerance capacity, the ultrastructural changes could be either a sign of toxicity that limits plant development or an adaptive strategy to cope with Pb stress. This paper gathers data on Pb-induced changes in cell ultrastructure observed in many tolerant and hyperaccumulator plants and describes the ultrastructural changes that appear to be mechanisms to alleviate Pb toxicity. The different modifications caused by Pb in cell organelles are summarized and reinforced with hypotheses that provide an overview of plant responses to Pb stress and explain the physiological and morphological changes that occur in tolerant plants. These ultrastructural modifications could help assess the potential of plants for use in phytoremediation.

Harnessing Lignocellulosic Crops for Phytomanagement of Contaminated Soils: A Multi-Country Study

The dwindling availability of agricultural land, caused by factors such as rapid population growth, urban expansion, and soil contamination, has significantly increased the pressure on food production. To address this challenge, cultivating non-food crops on contaminated land has emerged as a promising solution. This approach not only frees up fertile soil for food production but also mitigates human exposure to contaminants. This work aimed to examine the impact of soil contamination with Cd, Pb, Ni, and Zn on the growth, productivity, metal accumulation, and the tolerance of five lignocellulosic non-food crops: switchgrass (Panicum virgatum L.), biomass sorghum (Sorghum bicolor L. Moench), giant reed (Arundo donax L.), African fodder cane (Saccharum spontaneum L. spp. aegyptiacum Willd. Hackel), and miscanthus (Miscanthus × giganteus Greef et Deu.). A two-year pot experiment was conducted in Greece, Italy, and Portugal, following the same protocols and applying various levels of metals: Cd (0, 4, 8 mg kg−1), Pb and Zn (0, 450, 900 mg kg−1), and Ni (0, 110, 220 mg kg−1). The experimental design was completely randomized, with three replicates for each treatment. The results showed that switchgrass and sorghum generally maintained their height and productivity under Cd and Pb stress but were adversely affected by high Zn and Ni concentrations. Giant reed and African fodder cane showed reduced height and productivity at higher Ni and Zn levels. Miscanthus exhibited resilience in height but experienced productivity reductions only at the highest Zn concentration. Heavy metal uptake varied among crops, with switchgrass and sorghum showing high Cd and Pb uptake, while giant reed accumulated the most Cd and Zn. Miscanthus had the highest Ni accumulation. The tolerance indices indicated that switchgrass and sorghum were more tolerant to Cd and Zn at lower concentrations, whereas miscanthus had lower tolerance to Cd but a higher tolerance to Zn at higher concentrations. Giant reed and African fodder cane demonstrated stable tolerance across most heavy metals. Accumulation indices highlighted the effectiveness of switchgrass and sorghum in Cd and Pb uptake, while miscanthus excelled in Ni and Zn accumulation. The cluster analysis revealed similar responses to heavy metal stress between African fodder cane and giant reed, as well as between sorghum and miscanthus, with switchgrass displaying distinct behavior. Overall, the study highlights the differential tolerance and accumulation capacities of these crops, indicating the potential for phytoremediation applications and biomass production in heavy metal-contaminated soils.

The dynamic roles of intracellular vacuoles in heavy metal detoxification by Rhodotorula mucilaginosa.

Rhodotorula mucilaginosa (Rho) can develop a range of strategies to resist the toxicity of heavy metals. This study aimed to investigate the physiological responses and transcriptomic regulation of the fungus under different heavy metal stresses. This study applied transmission electron microscopy and RNA-seq to investigate the fungal resistance to Pb, Cd, and Cu stresses. Under Pb stress, the activated autophagy-related genes, vesicle-fusing ATPase, and vacuolar ATP synthase improved vacuolar sequestration. This offsets the loss of lipids. However, the metal sequestration by vacuoles was not improved under Cd stress. Vacuolar fusion was also inhibited following the interference of intravacuolar Ca2+ due to their similar ionic radii. Cu2+ showed the maximum toxic effects due to its lowest cellular sorption (as low as 7%) with respect to Pb2+ and Cd2+, although the efflux pumps and divalent metal ion transporters partially contributed to the detoxification. Divalent cation transporters and vacuolar sequestration are the critical strategies for Rho to resist Pb stress. Superoxide dismutase (SOD) is the main strategy for Cd resistance in Rho. The intracellular Cu level was decreased by efflux pump and divalent metal ion transporters.

Impact of Cd and Pb on the photosynthetic and antioxidant systems of Hemerocallis citrina Baroni as revealed by physiological and transcriptomic analyses.

Cd induces photosynthetic inhibition and oxidative stress damage in H. citrina, which mobilizes the antioxidant system and regulates the expression of corresponding genes to adapt to Cd and Pb stress. Cd and Pb are heavy metals that cause severe pollution and are highly hazardous to organisms. Physiological measurements and transcriptomic analysis were combined to investigate the effect of 5mM Cd or Pb on Hemerocallis citrina Baroni. Cd significantly inhibited H. citrina growth, while Pb had a minimal impact. Both Cd and Pb suppressed the expression levels of key chlorophyll synthesis genes, resulting in decreased chlorophyll content. At the same time, Cd accelerated chlorophyll degradation. It reduced the maximum photochemical efficiency of photosystem (PS) II, damaging the oxygen-evolving complex and leading to thylakoid dissociation. In contrast, no such phenomena were observed under Pb stress. Cd also inhibited the Calvin cycle by down-regulating the expression of Rubisco and SBPase genes, ultimately disrupting the photosynthetic process. Cd impacted the light reaction processes by damaging the antenna proteins, PS II and PS I activities, and electron transfer rate, while the impact of Pb was weaker. Cd significantly increased reactive oxygen species and malondialdehyde accumulation, and inhibited the activities of antioxidant enzymes and the expression levels of the corresponding genes. However, H. citrina adapted to Pb stress by the recruitment of antioxidant enzymes and the up-regulation of their corresponding genes. In summary, Cd and Pb inhibited chlorophyll synthesis and hindered the light capture and electron transfer processes, with Cd exerting great toxicity than Pb. These results elucidate the physiological and molecular mechanisms by which H. citrina responds to Cd and Pb stress and provide a solid basis for the potential utilization of H. citrina in the greening of heavy metal-polluted lands.

Gut dysbiosis of Rana zhenhaiensis tadpoles after lead (Pb) exposure based on integrated analysis of microbiota and gut transcriptome

Lead (Pb) is a ubiquitously detected heavy metal pollutant in aquatic ecosystems. Previous studies focused mainly on the response of gut microbiota to Pb stress, with less emphasis on gene expression in intestine, thereby limiting the information about impacts of Pb on intestinal homeostasis in amphibians. Here, microbial community and transcriptional response of intestines in Rana zhenhaiensis tadpoles to Pb exposure were evaluated. Our results showed that 10 μg/L Pb significantly decreased bacterial diversity compared to the controls by the Simpson index. Additionally, 1000 μg/L Pb exposure resulted in a significant reduction in the abundance of Fusobacteriota phylum and Cetobacterium genus but a significant expansion in Hafnia-Obesumbacterium genus. Moreover, transcriptome analysis revealed that about 90 % of the DEGs (8458 out of 9450 DEGs) were down-regulated in 1000 μg/L Pb group, mainly including genes annotated with biological functions in fatty acid degradation, and oxidative phosphorylation, while up-regulated DEGs involved in metabolism of xenobiotics by cytochrome P450. The expression of Gsto1, Gsta5, Gstt4, and Nadph showed strong correlation with the abundance of genera Serratia, Lactococcus, and Hafnia-Obesumbacterium. The findings of this study provide important insights into understanding the influence of Pb on intestinal homeostasis in amphibians.

Phytoremediation of Pb-polluted soil using bermudagrass: Effect of mowing frequencies

Plant lead (Pb) tolerance and accumulation are key characteristics affecting phytoremediation efficiency. Bermudagrass is an excellent candidate for the remediation of Pb-polluted soil, and it needs to be mowed regularly. Here, we explored the effect of different mowing frequencies on the remediation of Pb-contaminated soil using bermudagrass. Mowing was found to decrease the biomass and photosynthetic efficiency of bermudagrass under Pb stress, thereby inhibiting its growth. Although mowing exacerbated membrane peroxidation, successive mowing treatments alleviated peroxidation damage by regulating enzymatic and nonenzymatic systems. A comprehensive evaluation of Pb tolerance revealed that all the mowing treatments reduced the Pb tolerance of bermudagrass, and a once-per-month mowing frequency had a less negative effect on Pb tolerance than did more frequent mowing. In terms of Pb enrichment, mowing significantly increased the Pb concentration, total Pb accumulation, translocation factor (TF), and bioenrichment factor (BCF) of bermudagrass. The total Pb accumulation was greatest under the once-a-month treatment, while the TF and BCF values were greatest under the three-times-a-month mowing treatment. Additionally, the decrease in soil pH and DOC were significantly correlated with the soil available Pb content and plant Pb accumulation parameters. The results showed that changes in the rhizosphere are crucial factors regulating Pb uptake in bermudagrass during mowing. Overall, once-a-month mowing minimally affects Pb tolerance and maximizes Pb accumulation, making it the optimal mowing frequency for soil Pb remediation by bermudagrass. This study provides a novel approach for the remediation of Pb-contaminated soil with bermudagrass based on mowing.

Multivariate characterization of salicylic acid and potassium induced physio-biochemical and phytoremediation responses in quinoa exposed to lead and cadmium contamination

The levels of soils pollutants such as lead (Pb) and cadmium (Cd) have significantly increased recently resulting in ecological disturbances and threatening crop production. Various amendments have been employed to enhance the tolerance of crops to withstand Cd and Pb stresses. However, the role of combined application of potassium (K) and of salicylic acid (SA) for Cd and Pb stress mitigation and phytoremediation by quinoa (Chenopodium quinoa Willd) has not been comprehended well. In the present study, the effect of 10 mM K and 0.1 mM SA was tested on the quinoa plants subjected to 250 μM Pb and/or 100 μM Cd. The Pb and Cd treatments were applied separately or together. Phytotoxicity induced by Pb and Cd resulted in drastic decrease (>60%) in chlorophyll contents, stomatal conductance, and plant biomass. The collective treatment of Pb and Cd induced an increase in the concentration of hydrogen peroxide (13-fold) and lipid peroxidation (16-fold) that resulted in a 61% reduction in membrane stability. The application of 10 mM K and/or 0.1 mM SA was remarkable in mitigating the adverse effect of Pb and Cd. The reduction in plant biomass was 17% when 10 mM K and 0.1 mM SA were applied together under the combined treatment of both the metals. The simultaneous application of K and SA effectively mitigated oxidative stress by enhancing the activities of superoxide dismutase, peroxidase, ascorbate peroxidase, and catalase by 12, 10, 7 and 10-folds respectively. The positive effect of K and SA on these attributes resulted in a remarkable reduction in metal accumulation and translocation and lipid peroxidation. The stressed plants supplemented with K and SA exhibited a significant improvement in the membrane stability index, chlorophyll content, and stomatal conductance. This study concluded that the combined application of K and SA could be a good approach for reducing Pb and Cd phytotoxicity in quinoa and enhancing their phytostabilization potential in the contaminated soils.

Screening and Stress Responsive Characteristics of Potential Hyperaccumulator of Pb, Zn, and Cd Compound Heavy Metals

To screen for Pb, Zn, and Cd composite heavy metal hyperaccumulator plants, a survey, sampling, and analysis of dominant plants in typical lead-zinc mines and smelter areas in Baoji City were conducted. Potential Pb, Zn, and Cd composite heavy metal hyperaccumulator plants were initially screened, and a pot experiment of soil cultivation was carried out to observe the response characteristics of chlorophyll （chlorophyll a, chlorophyll b, carotenoids, and total chlorophyll）, antioxidant enzymes （SOD, CAT, and POD）, and other physiological indicators （MDA and proline） under the stress of Pb, Zn, and Cd composite heavy metals. A field experiment was also conducted to further verify and determine their enrichment ability for Pb, Zn, and Cd composite heavy metals, aiming to provide scientific basis and technical support for the remediation of Pb, Zn, and Cd composite heavy metal-polluted soil. The field survey revealed that Symphytum officinale L. met the international hyperaccumulator plant index requirements for the enrichment of Pb, Zn, and Cd, with enrichment quantity, bioconcentration factor （BCF）, and transfer factor （TF） all meeting the requirements. It was a potential hyperaccumulator plant for Pb, Zn, and Cd composite heavy metals. The soil cultivation pot experiment showed that as the gradient of Pb, Zn, and Cd composite heavy metal stress increased, the content of chlorophyll a, chlorophyll b, and total chlorophyll in S. officinale L. leaves gradually decreased, causing disruption to the plant's photosynthetic system when the gradient was greater than or equal to IV. The chlorophyll content in Ricinus communis L. leaves exhibited a "low-stimulation-high-inhibition" phenomenon, while excessive stress stimulated the activation of its own protective systems, leading to reduced toxicity. In addition, there were significant differences （P < 0.05） in the content of chlorophyll a, chlorophyll b, carotenoids, and total chlorophyll between S. officinale L. and R. communis L. both compared to the control treatment and between stress gradients. The SOD activity in the leaves of S. officinale L. and R. communis L. showed a trend of increasing first, then decreasing, and then increasing. The CAT activity in the leaves of S. officinale L. exhibited a "low-stimulation-high-inhibition" effect, whereas the CAT activity in the leaves of R. communis L. showed a trend of continuous decrease. The POD activity in the leaves of S. officinale L. generally increased, whereas in the leaves of R. communis L., it increased first, then decreased, and then increased. The MDA content in the leaves of S. officinale L. generally decreased, whereas in the leaves of R. communis L., it exhibited an upward trend. In addition, whether compared to the control between stress gradients, there were significant differences （P < 0.05） in the SOD, CAT, POD, MDA, and proline content of S. officinale L. and R. communis L. The field experiment results indicated that S. officinale L. could meet the hyperaccumulator plant index requirements for the enrichment of Pb, Zn, and Cd, making it a potential germplasm resource for Pb, Zn, and Cd composite heavy metal hyperaccumulator plants. It can be an ideal choice for the remediation of Pb, Zn, and Cd composite heavy metal-polluted soil.

A phased small interfering RNA-derived pathway mediates lead stress tolerance in maize.

Phased small interfering RNAs (phasiRNAs) are a distinct class of endogenous small interfering RNAs, which regulate plant growth, development and environmental stress response. To determine the effect of phasiRNAs on maize (Zea mays L.) tolerance to lead (Pb) stress, the roots of 305 maize lines under Pb treatment were subjected to generation of individual databases of small RNAs. We identified 55 high-confidence phasiRNAs derived from 13 PHAS genes (genes producing phasiRNAs) in this maize panel, of which 41 derived from nine PHAS loci were negatively correlated with Pb content in the roots. The potential targets of the 41 phasiRNAs were enriched in ion transport and import. Only the expression of PHAS_1 (ZmTAS3j, Trans-Acting Short Interference RNA3) was regulated by its cis-expression quantitative trait locus and thus affected the Pb content in the roots. Using the Nicotiana benthamiana (N. benthamiana) transient expression system, 5'-rapid amplification of cDNA ends, and Arabidopsis heterologously expressed, we verified that ZmTAS3j was cleaved by zma-miR390 and thus generated tasiRNA targeting ARF genes (tasiARFs), and that the 5' and 3' zma-miR390 target sites of ZmTAS3j were both necessary for efficient biosynthesis and functional integrity of tasiARFs. We validated the involvement of the zma-miR390-ZmTAS3j-tasiARF-ZmARF3-ZmHMA3 pathway in Pb accumulation in maize seedlings using genetic, molecular, and cytological methods. Moreover, the increased Pb tolerance in ZmTAS3j-overexpressed lines was likely attributed to the zma-miR390-ZmTAS3j-tasiARF-ZmARF3-SAURs pathway, which elevated indole acetic acid levels and thus reactive oxygen species scavenging capacity in maize roots. Our study reveals the importance of the TAS3-derived tasiRNA pathway in plant adaptation to Pb stress.

Nondestructive detection of lead content in oilseed rape leaves under silicon action using hyperspectral image

This study explored the feasibility of employing hyperspectral imaging (HSI) technology to quantitatively assess the effect of silicon (Si) on lead (Pb) content in oilseed rape leaves. Aiming at the defects of hyperspectral data with high dimension and redundant information, this paper proposed two improved feature wavelength extraction algorithms, repetitive interval combination optimization (RICO) and interval combination optimization (ICO) combined with stepwise regression (ICO-SR). The entire oilseed rape leaves were taken as the region of interest (ROI) to extract the visible near-infrared hyperspectral data within the 400.89–1002.19 nm range. In data processing, Savitzky-Golay (SG) smoothing, detrending (DT), and multiple scatter correction (MSC) were utilized for spectral data preprocessing, while recursive feature elimination (RFE), iteratively variable subset optimization (IVSO), ICO, and the two enhanced algorithms were employed to identify characteristic wavelengths. Subsequently, based on the spectral data of preprocessing and feature extraction, partial least squares regression (PLSR) and support vector regression (SVR) methods were used to construct various Pb content prediction models in oilseed rape leaves, with a comparison and analysis of each model performance. The results indicated that the two improved algorithms were more efficient in extracting representative spectral information than conventional methods, and the performance of SVR models was better than PLSR models. Finally, to further improve the prediction accuracy and robustness of the SVR models, the whale optimization algorithm (WOA) was introduced to optimize their parameters. The findings demonstrated that the MSC-RICO-WOA-SVR model achieved the best comprehensive performance, with Rp2 of 0.9436, RMSEP of 0.0501 mg/kg, and RPD of 3.4651. The results further confirmed the great potential of HSI combined with feature extraction algorithms to evaluate the effectiveness of Si in alleviating Pb stress in oilseed rape and provided a theoretical basis for determining the appropriate amount of Si application to alleviate Pb pollution in oilseed rape.