Organic nitrogen availability is increasingly recognized as a regulatory factor shaping plant metabolic organization beyond its nutritional role. This study investigates the regulatory function of exogenous glutamate (Glu) in Nicotiana tabacum L., focusing on its spatial compartmentalization between the apoplast and symplast and its role in carbon-nitrogen metabolic regulation. Using a method for separately extracting apoplastic and symplastic solutions, we analyzed the distribution of free amino acids in roots and shoots under different Glu supplies (0, 0.05, and 1 mM). Exogenous Glu was preferentially assimilated in the root symplast and rapidly converted into glutamine (Gln), which served as the dominant organic nitrogen form for long-distance transport via the xylem. In leaves, organic nitrogen accumulated mainly as amino acids in the apoplast, contributing to nitrogen buffering and compartment-specific partitioning. In roots, elevated Glu supply induced coordinated reprogramming of carbon-nitrogen metabolism, including activation of the gamma-aminobutyric acid (GABA) shunt, restructuring of the tricarboxylic acid cycle, and enhancement of jasmonate-and nicotine-associated secondary metabolism. Transcriptomic analyses further revealed Glu-dependent regulation of key genes involved in these processes. Collectively, these findings identify exogenous Glu as an important regulatory factor integrating organic nitrogen assimilation, metabolic reprogramming, and secondary metabolism.

Amino acid transport is essential for organic nitrogen acquisition and signaling in plants, yet the transporter-level mechanisms underlying glutamate (Glu) responses remain unclear, especially in polyploid crops. Here, we conducted a genome-wide identification and expression analysis of amino acid transporter (AAT) genes in allotetraploid tobacco (Nicotiana tabacum). We identified 182 AAT genes and classified them into 12 subfamilies based on phylogenetic relationships with Arabidopsis thaliana and rice (Oryza sativa). Chromosomal mapping revealed an uneven distribution with prominent tandem clusters, and duplicated gene pairs were predominantly under purifying selection, suggesting overall functional constraint after polyploidization. RNA-seq analysis showed that Glu triggers time- and dose-dependent transcriptional reprogramming of AAT genes, with substantially stronger and more coordinated responses in roots than in shoots. 23 AAT genes were identified as Glu-responsive candidates in roots, mainly from the LHT, AAP, and ProT subfamilies. Correlation-based network analysis further highlighted 22 transcription factors strongly associated with these transporters, including seven core hub regulators. qRT-PCR validation of five key Glu-responsive AAT genes confirmed the transcriptome data. Promoter analysis revealed enrichment of MYB-, bZIP/bHLH-, and WRKY-related motifs, along with hormone- and stress-responsive elements, supporting transcription factor–mediated regulation. Physiological and phenotypic analyses indicated that Glu treatment promoted carbon and nitrogen accumulation, increased shoot biomass and root-to-shoot ratio, while exerting minimal effects on leaf area and root morphology in tobacco seedlings. These results propose a regulatory framework linking Glu signaling to AAT expression in tobacco roots and provide candidate genes for improving organic nitrogen utilization, providing theoretical support and genetic resources for improving nitrogen use efficiency in polyploid crops.

Soil and water contamination by cadmium (Cd2⁺) poses serious environmental and health risks, requiring efficient and sustainable remediation strategies. Although biochar has been widely applied for metals removal, systematic comparisons of different chemical modification methods and their adsorption mechanisms remain limited. This study presents a comparative evaluation of four chemically modified tobacco-stem biochars, including H₂O₂-modified (H-BC), KMnO₄-modified (K-BC), alkali-modified (Na-BC), and Fe-loaded magnetic biochar (Fe-BC), for Cd2⁺ removal. Surface characterization revealed that K-BC enhanced oxygen-containing functional groups (-COOH, -CHO), while Fe-BC exhibited the highest surface area (68.79 m2/g). Adsorption experiments showed that K-BC and Fe-BC achieved nearly 100

The contamination of plants with heavy metals (HMs) represents a significant threat to agricultural sustainability, severely impairing plant growth, physiology, and productivity through toxic effects. To withstand and adapt to metal stress, plants have evolved intricate defense systems encompassing morphological, physiological, biochemical, and molecular responses. This review synthesizes current understanding of metal uptake, translocation and cellular compartmentalization with emphasis on detoxification pathways such as chelation by metallothioneins and phytochelatins, organic acid exudation and the roles of metal transporters and regulatory proteins. We further highlight the regulatory influence of key transcription factors, including WRKY, MYB, and NAC families, which orchestrate complex gene networks underlying metal tolerance. Advances in proteomic and metabolomic studies have revealed transiently expressed proteins and dynamic metabolic shifts that underpin enhanced resilience under metal exposure. In addition, we examine emerging phytoremediation techniques and cutting-edge biotechnological strategies that offer promising avenues to boost plant tolerance and remediation efficiency. Looking ahead, future research should aim to unravel the intricate signaling cascades and transcriptional regulatory cascades governing metal stress responses, ultimately paving the way for the development of genetically engineered crops capable of sustaining productivity and supporting environmentally responsible remediation practices.

Microplastic pollution increasingly threatens agricultural ecosystems, yet how different microplastic types interact with plants remains largely unknown. Here, we systematically compared the uptake, translocation, and physiological impacts of polystyrene (PS) microspheres and polyacrylonitrile (PAN) microfibers in hydroponically grown tobacco. We identified distinct root entry pathways: PS microspheres penetrated via the root apex and lateral root initiation sites, whereas PAN microfibers infiltrated exclusively through intercellular gaps at lateral root emergence, failing to cross the root apex. Both types subsequently translocated to aerial tissues, with PS microspheres demonstrating significantly higher root uptake, retention, and shoot translocation efficiency than PAN microfibers. Growth responses were strongly type- and concentration-dependent: PS microspheres inhibited growth, photosynthesis, and root development at ≥ 1mg/L, while PAN microfibers promoted growth over a broader range (0.1–10mg/L), becoming inhibitory only at ≥ 50mg/L. PS exposure induced more pronounced disruptions in nitrogen assimilation, carbon metabolism, and key hormone signaling (ethylene, auxin, cytokinin, gibberellin), alongside greater reactive oxygen species (ROS) accumulation and intensified antioxidant responses. Transcriptomic analyses corroborated these physiological findings, revealing stronger activation of stress-responsive genes under PS treatment. This study reveals that structurally distinct microplastics differ not only in uptake and translocation efficiency, but also in root entry pathways and downstream physiological and transcriptomic responses, identifying microplastic morphology as a key determinant of plant phytotoxicity. These findings provide important insights for ecological risk assessment and mitigation of agricultural microplastic pollution.

Cadmium (Cd), a pervasive and highly phytotoxic metal pollutant, poses severe threats to agricultural productivity, ecosystem stability, and human health through its entry into the food chain. Plants have evolved intricate defense mechanisms, among which the strategic manipulation of nutrient elements emerges as a critical physiological and biochemical strategy for mitigating Cd stress. This comprehensive review delves deeply into the multifaceted roles of essential macronutrient elements (nitrogen, phosphorus, potassium, calcium, magnesium, sulfur), essential micronutrient elements (zinc, iron, manganese, copper) and non-essential beneficial elements (silicon, selenium) in modulating plant responses to Cd toxicity. We meticulously dissect the physiological, biochemical, and molecular underpinnings of how these nutrients influence Cd bioavailability in the rhizosphere, Cd uptake and translocation pathways, sequestration and compartmentalization within plant tissues, and the activation of antioxidant defense systems. Nutrient elements exert their influence through diverse mechanisms: competing with Cd for root uptake transporters, promoting the synthesis of complexes that reduce Cd mobility, stabilizing cell walls and plasma membranes to restrict apoplastic flow and symplastic influx, modulating redox homeostasis by enhancing antioxidant enzyme activities and non-enzymatic antioxidant pools, regulating signal transduction pathways, and influencing gene expression profiles related to metal transport, chelation, and detoxification. The complex interactions between nutrients themselves further shape the plant’s capacity to withstand Cd stress. Recent advances elucidating nutrient-mediated epigenetic regulation, microRNA involvement, and the role of nutrient-sensing signaling hubs in Cd responses are critically evaluated. Furthermore, we synthesize the practical implications of nutrient management strategies, including optimized fertilization regimes, selection of nutrient-efficient genotypes, and utilization of nutrient-enriched amendments, for enhancing phytoremediation efficiency and developing low-Cd-accumulating crops, thereby contributing to safer food production and environmental restoration in Cd-contaminated soils. The intricate interplay between plant nutritional status and Cd stress resilience underscores the necessity for a holistic, nutrient-centric approach in managing Cd toxicity in agroecosystems.

Cadmium (Cd) contamination presents a significant challenge in global agriculture. This study explores the efficacy of chemical induction, specifically using sodium chloride (NaCl), to limit Cd uptake in tobacco (Nicotiana tabacum) and assesses its impact on essential divalent metal ions (DMIs). We conducted a comprehensive analysis encompassing ion absorption, root histology, and biochemistry to understand the influence of this method. Our results revealed that NaCl induction led to a notable 30 % decrease in Cd absorption, while maintaining minimal impact on zinc (Zn) uptake. Intriguingly, the absence of essential DMIs, such as calcium (Ca), magnesium (Mg), and Zn, was found to diminish the plant's capacity to absorb Cd. Furthermore, moderate NaCl induction resulted in an increased diameter of the root stele and enhanced lignin content, indicating a restriction of Cd absorption through the apoplastic pathway. Conversely, a compensatory absorption mechanism via the symplastic pathway appeared to be activated in the absence of essential elements. These findings highlight the potential of chemical induction as a strategy to mitigate agricultural Cd risks, offering insights into the complex interplay between plant ion transport pathways and metal uptake regulation.

Nitrogen levels and distribution in the rhizosphere strongly regulate the root architecture. Nitrate is an essential nutrient and an important signaling molecule for plant growth and development. Hydroponic experiments were conducted to investigate the differences in endodermal suberization in tobacco (Nicotiana tabacum L.) roots at three nitrate levels. Nitrogen accumulation was detected in the roots, shoots, and xylem sap. Nitrate influx on the root surface was also measured using the non-invasive self-referencing microsensor technique (SRMT). RNA-Seq analysis was performed to identify the genes related to endodermal suberization, nitrate transport, and endogenous abscisic acid (ABA) biosynthesis. The results showed that root length, root-shoot ratio, nitrate influx on the root surface, and NiA and NRT2.4 genes were regulated to maintain the nitrogen nutrient supply in tobacco under low nitrate conditions. Low nitrate levels enhanced root endodermal suberization and hence reduced the apoplastic transport pathway, and genes from the KCS, FAR, PAS2, and CYP86 families were upregulated. The results of exogenous fluridone, an ABA biosynthesis inhibitor, indicated that suberization of the tobacco root endodermis had no relevance to radial nitrate transport and accumulation. However, ABA enhances suberization, relating to ABA biosynthesis genes in the CCD family and degradation gene ABA8ox1.

Tobacco (Nicotiana tabacum L.) is a potential phytoremediator that can reduce soil cadmium (Cd) contamination. Pot and hydroponic experiments were conducted to investigate the difference in absorption kinetics, translocation patterns, accumulation capacity, and extraction amounts between two leading tobacco cultivars in China. We studied the chemical forms and subcellular distribution of Cd in the plants to understand the diversity of the detoxification mechanism of the cultivars. The concentration-dependent kinetics of Cd accumulation in leaves, stems, roots, and xylem sap for cultivars Zhongyan 100 (ZY100) and K326, fitted well with the MichaelisMenten equation. K326 exhibited high biomass, Cd tolerance, Cd translocation, and phytoextraction abilities. The acetic acid, sodium chloride, and water-extractable fractions accounted for > 90% of Cd in all ZY100 tissues but only in K326 roots and stems. Moreover, the acetic acid and NaCl fractions were the predominant storage forms, while the water fraction was the transport form. The ethanol fraction also contributed significantly to Cd storage in K326 leaves. As the Cd treatment increased, more NaCl and water fractions were found in K326 leaves, while only NaCl fractions increased in ZY100 leaves. For subcellular distribution, > 93% Cd proportions were primarily stored in both cultivars' soluble or cell wall fraction. The proportion of Cd in the cell wall fraction of ZY100 roots was less than that of K326, while that proportion in the soluble fraction in ZY100 leaves was higher than in K326 leaves. These findings demonstrate that Cd accumulation patterns, detoxification, and storage strategies differ between the cultivars, providing a deeper understanding of Cd tolerance and accumulation mechanism in tobacco plants. It also guides the screening of germplasm resources or gene modification to improve the Cd phytoextraction efficiency of tobacco.

Sucrose (Suc) accumulation is one of the key indicators of leaf senescence onset, but little is known about its regulatory role. Here, we found that application of high (120–150 mM) and low levels (60 mM) of Suc to young leaf (YL) and fully expanded leaf (FEL) discs, respectively, decreased chlorophyll content and maximum photosynthetic efficiency. Electrolyte leakage and malondialdehyde levels increased at high Suc concentrations (90–120 mM in YL and 60 and 150 mM in FEL discs). In FEL discs, the senescence-associated gene NtSAG12 showed a gradual increase in expression with increased Suc application; in contrast, in YL discs, NtSAG12 was upregulated with low Suc treatment (60 mM) but downregulated at higher levels of Suc. In YL discs, trehalose-6-phosphate (T6P) accumulated at a low half-maximal effective concentration (EC50) of Suc (1.765 mM). However, T6P levels declined as trehalose 6 phosphate synthase (TPS) content decreased, resulting in the maximum velocity of sucrose non-fermenting-1-related protein kinase (SnRK) and hexokinase (HXK) occurring at higher level of Suc. We therefore speculated that senescence was induced by hexose accumulation. In FEL discs, the EC50 of T6P occurred at a low concentration of Suc (0.9488 mM); T6P levels progressively increased with higher TPS content, which inhibited SnRK activity with a dissociation constant (Kd) of 0.001475 U/g. This confirmed that the T6P–SnRK complex induced senescence in detached FEL discs.

Cadmium (Cd) is known as one of the most hazardous elements in the environment and a persistent soil constraint toxic to all flora and fauna. In this study, we conducted physiological, biochemical, and transcriptomic analyses of Nicotiana rustica (N. rustica) and Nicotiana tabacum (N. tabacum) treated with CdCl2 to know the underlying molecular mechanisms of Cd accumulation. As a result, N. rustica had more dry weight than N. tabacum. Additionally, N. rustica accumulated higher Cd concentration (69.65 times), Cd2+ influx (1.32-fold), glutathione S-transferases (GST) enzyme activity (2.54 times), GSH/GSSG (oxidized form of GSH) ratio, increase of superoxide dismutase and CAT and a lower H2 O2 and superoxide (O2 •- ) accumulation in their roots than N. tabacum. Cd mainly distributed in the cytoplasm of both species and N. rustica had a significant proportion in the cell wall. Furthermore, the transcriptomic analysis revealed 173 and 710 differentially expressed genes (DEGs) between control and Cd-stressed plants in the leaves and roots of N. rustica, while 576 and 1543 DEGs were found in the leaves and roots of N. tabacum, respectively. In N. rustica, phenylpropanoid biosynthesis and phenylalanine metabolism were the most enriched pathways, while GSH metabolism, ATP-binding cassette transporters and phenylpropanoid biosynthesis were the most enriched in N. tabacum. Finally, we found that DEGs related to metal influx, sequestration, remobilization, and chelation were responsible for Cd accumulation. These results indicated that N. rustica accumulated higher Cd content than N. tabacum, suggesting that each species utilized different response mechanism under the same Cd stress conditions. The DEGs identified in this study might lead to the identification of genes or pathways related to Cd regulation. This study identifies important regulators related to Cd accumulation.

The heavy metals, including cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb), zinc (Zn), and the metalloid arsenic (As) were detected in surface and core soil samples collected from a tobacco growing region in Shandong Peninsula on the east coast of China to evaluate their pollution levels, ecological and health risks, and to analyze their spatial and vertical distributions. The heavy metal sources were identified quantitatively using the positive matrix factorization (PMF) receptor model. In accordance, most of the soils did not have accumulations and were not contaminated by As, Cr, Cu, Ni, Pb, and Zn. High accumulations of Cd and Hg occurred in the soils, posing an ecological risk to the local agricultural environment, while Cr and Ni levels presented a carcinogenic health risk to humans. Four main sources of heavy metals in the soils were identified. Correspondingly Ni and Cr were mainly originated from natural sources, Hg from coal combustion, Cd from agricultural practices, Cu, Pb, and Zn from agricultural practices and industrial activities, and As from industrial activities.

Cadmium (Cd) pollution threatens agricultural security worldwide. This study tested the efficacy of priming chemicals to decrease Cd uptake by tobacco plants (Nicotiana tabacum). After initial screening from nine different chemicals (NaCl, Cd(CH3COO)2, Cd(NO3)2, CdCl2, KHNO3, polyethylene glycol 6000 (PEG-6000), indole-3-acetic acid (IAA), ß-aminobutyric acid (BABA), and glutathione (GSH)), NaCl and PEG-6000 were further investigated because of their low risks to plant growth and efficiency to Cd reduction. Priming procedures (concentrations) were optimized for both chemicals and the best one (100 mM NaCl) was used to test both soil and hydroponic media. The results showed 31.3% lower Cd concentrations in shoots after priming with 100 mM NaCl. Phenotype parameters of the plants were also measured and showed no significant impacts of the priming procedures on the shoot biomass and the uptakes of nitrogen (N), phosphorus (P), and potassium (K), nor the photosynthetic capacity (net photosynthesis rate (Pn) and chlorophyll concentration (SPAD)). Histological observations of the roots showed a significant increase of the stele diameter after NaCl priming and a subsequent negative correlation between shoot Cd concentration and stele diameter was found after NaCl priming at different levels. This study confirmed 100 mM NaCl as an efficient priming treatment to decrease Cd uptake and the coarsening of the root stele was identified as a potential explanation for the observed decrease of Cd in tobacco shoots.

Cadmium (Cd) contamination is one of the most serious global environmental problems, and phytoremediation, which uses Cd-accumulator plants, is potentially one of the sustainable solutions. Pot experiments with natural and Cd-amended soils were conducted to investigate the accumulation of heavy metals in 10 leading cultivars of tobacco in China. The extraction ability and profiles of Cd accumulation among plant organs were also analyzed. The tobacco roots accumulated cobalt, nickel, and Cd, while the leaf highly bioaccumulated Cd and lowly accumulated zinc, selenium and mercury. The transport from the tobacco stem to the leaf plays a critical role in the accumulation of these elements. The ratios of Cd concentration in the leaves at lower, middle and upper positions were comparatively stable. The high Cd-extracting cultivars were "Hongda", "NC89" and "Zhongyan 100" when grown in normal soils, "CuiBi 1" and "Hongda" in moderately contaminated soils, and "YuYan 87", "LongJiang 851" and "K326" in severely contaminated soils. Tobacco leaves could accumulate about 80% of the total Cd extracted from the soil by the plant. Considering the Cd-extraction limitations exhibited by leading tobacco cultivars, screening of germplasm resources for high or low levels of Cd-accumulation is still an important target for the future.

在黄泛区高液限黏土中添加不同剂量的石灰、粉煤灰和石灰粉煤灰,通过液塑限试验探究材料液限、塑性指数随时间变化的规律,确定最优的改性剂量与效果.试验表明:黄泛区高液限黏土主要矿物含量为伊利石、蒙脱石及高岭石,亲水性好,液限在50％左右;具有膨胀性、易泡散、水稳定性差等缺点,浸水4 d的承载比(CBR)低于3％;二灰土中石灰外掺4％、石灰与粉煤灰配合比3:9均可降低材料的亲水性、膨胀性,提高水稳定性,在88％压实度下改性土4 d浸水CBR能达8％,满足路床区填料要求.

The heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) in the surface soils of tobacco (Nicotiana tabacum L.) fields in Jiangxi Province were analyzed, and the mean heavy metal concentrations were 3.55, 0.19, 25.89, 14.96, 0.25, 10.89, 27.80, and 44.00 mg/kg, respectively. Spatial distribution analysis showed that the highest concentrations were recorded in the north-western, south-western, and mid-eastern parts of the study area. The index of geo-accumulation and pollution index indicated modest enrichment with Cd and Hg, which were the only two metals posing a potentially high ecological risk to the local agricultural environment. The health risk assessment showed no considerable non-carcinogenic or carcinogenic risks for children and adults from these elements. The principal component analysis (PCA) and cluster analysis (CA) found that the variations in the Cr and Ni concentrations were largely on account of the soil parent rocks, but the As, Cd, Cu, and Hg variations in the soil were largely owing to agricultural practices of years. However, the main factor influencing Pb and Zn was atmospheric deposition.

Samples of surface soil from tobacco (Nicotiana tabacum L.) fields were analysed for heavy metals and showed the following concentrations (mean of 246 samples, mg/kg): As, 5.10; Cd, 0.11; Cr, 49.49; Cu, 14.72; Hg, 0.08; Ni, 19.28; Pb. 20.20 and Zn, 30.76. The values of the index of geoaccumulation (I geo) and of the enrichment factor indicated modest enrichment with As, Cd, Cr, Hg, Ni or Pb. Principal component analysis and cluster analysis correctly allocated each investigated element to its source, whether anthropogenic or natural. The results were consistent with estimated inputs of heavy metals from fertilizers, irrigation water and atmospheric deposition. The variation in the concentrations of As, Cd, Cu, Pb and Zn in the soil was mainly due to long-term agricultural practises, and that of Cr and Ni was mainly due to the soil parent material, whereas the source of Hg was industrial activity, which ultimately led to atmospheric deposition. Atmospheric deposition was the main exogenous source of heavy metals, and fertilizers also played an important role in the accumulation of these elements in soil. Identifying the sources of heavy metals in agricultural soils can serve as a basis for appropriate action to control and reduce the addition of heavy metals to cultivated soils.

Tobacco plants grown in pots and in hydroponic culture accumulated cadmium (Cd) particularly: the Cd content of tobacco leaves exceeded 100 mg/kg and the enrichment factor (the ratio of Cd in leaves to that in soil) was more than 4. These high levels of accumulation identify tobacco as a hyperaccumulator of Cd. Two transpiration inhibitors (paraffin or CaCl2) and shade decreased the Cd content of tobacco leaves, and the decrease showed a linear relationship with the leaf transpiration rate. A metabolism inhibitor, namely 2,4-dinitrophenol (DNP), and low temperature (4 °C) also lowered the Cd content of tobacco leaves, but the inhibitory effect of low temperature was greater. In the half number of leaves that were shaded, the Cd content decreased to 26.5% of that in leaves that were not shaded in the same tobacco plants. These results suggests that translocation of Cd from the medium to the leaves is driven by the symplastic and the apoplastic pathways. Probably, of the two crucial steps in the translocation of Cd in tobacco plants, one, namely uptake from the medium to the xylem, is energy-dependent whereas the other, namely the transfer from the xylem to the leaves, is driven mainly by transpiration.

采用田间小区试验,通过外源添加1.5 mg kg-1镉(Cd)模拟轻度Cd污染土壤,研究赤泥、油菜秸秆、玉米秸秆及其组合并配施硫酸锌降低土壤Cd有效性和烟草各部位Cd含量的长期效果.结果表明,施用钝化剂后,烟叶产量增加了7.0％～32.1％,中上等烟叶比例提高了2.9％～20.2％,烟草经济效益提高了6.6％～31.3％.钝化剂处理土壤有效态Cd含量降低显著,2012年和2013年降幅分别为18.6％～47.4％、16.0％～27.0％.烟草各部位Cd含量排序为下部叶＞中部叶、上部叶＞茎秆,且均与土壤有效态Cd含量呈极显著正相关关系.2011-2013年钝化剂处理烟草叶片Cd平均含量较对照分别降低了28.3％、28.1％、15.2％,烟草各部位Cd含量年变化幅度下部叶最大,茎秆最小,叶位间Cd含量差异随钝化时间延长逐渐缩小.钝化剂降低土壤-烟草系统Cd生物有效性效果稳定持久,其中油菜秸秆优于玉米秸秆,有机无机复合钝化剂效果最好.配施锌肥后,2011-2013年烟草叶片Cd含量较对照分别降低了19.1％、23.3％、17.9％,且下部和中部叶片降低效果达到显著水平;中部和上部叶Cd、Zn含量呈显著负相关关系.因此,在轻度Cd污染土壤上,赤泥油菜秸秆复合钝化剂配施锌肥是降低烟叶镉含量兼顾高产的最佳生产措施.