Search Results (140)

Litter decomposition regulates the quantity and quality of plant-derived carbon (C) and nitrogen (N) inputs to soil and is closely associated with microbial community structure. However, how elevated ozone (O₃) and nitrogen (N) addition interactively affect residual litter inputs and their associations with soil microbial communities remains poorly understood, especially in agroforestry systems. Here, we conducted a 12-month in situ litter decomposition experiment using two poplar clones (107 and 546) under ambient or elevated O₃ with or without N addition (60 kg N ha⁻¹ yr⁻¹) at an O₃-FACE platform in northern China. Litter mass and chemical traits were measured during decomposition, and endpoint soil microbial community structure was characterized using phospholipid fatty acid (PLFA) profiling. Treatment effects and litter–microbe associations were evaluated using linear mixed-effects models, correlation analysis, and redundancy analysis (RDA). Endpoint litter mass remaining was significantly affected by O₃, clone identity, and their interactions with N addition, while endpoint litter chemical traits showed trait-specific responses. PLFA-derived microbial community indices also showed treatment- and clone-dependent responses, particularly in bacterial groups, AM fungi, and the fungal-to-bacterial ratio. Endpoint litter mass remaining showed the strongest statistical association with PLFA-derived microbial community structure, whereas individual nutrient concentrations showed weaker independent effects. These findings suggest that O₃- and N-induced changes in residual litter quantity and quality are associated with shifts in PLFA-derived microbial community structure. Because PLFA characterizes microbial community structure rather than process rates, these findings should be interpreted as evidence of structural microbial reorganization associated with altered residual litter inputs, rather than direct evidence of changes in C or N cycling rates. Full article

A simple method for the efficient high-throughput transformation of hybrid poplar (Populus tremula x alba clone 717 1B) is described. Factors considered in developing the method included the ease and efficiency of preparing large numbers of explants for transformation, and selection of culture media that enhanced cell and tissue growth while promoting shoot regeneration competence. We found that petiole explants from in vitro-cultured plantlets can be easily collected and prepared for transformation and regenerate shoots comparable to stem or leaf explants. Culturing petiole explants on Driver Kuniyuki Walnut (DKW) medium resulted in significantly greater tissue growth compared to Murashige Skoog (MS) medium. Moreover, the inclusion of low concentrations of thidiazuron (TDZ) in callus-inducing media (CIM) significantly enhanced shoot regeneration competence of cultured petiole explants. As a consequence, the combination of petiole explants cultured on DKW medium along with 2.2 ug/L TDZ during the callus induction phase resulted in rapid and efficient transformation of this hybrid poplar genotype. When applied to genomic approaches such as activation tagging or CRISPR-Cas9 and Cas12a gene editing, we obtained transformation efficiencies ranging between 70% and 90%. The described protocol provides a simple and efficient method that is easily scalable for high-throughput approaches, which could facilitate genome-wide methods for the rapid and efficient production of transformed hybrid poplars. Full article

Plant growth-promoting rhizobacteria (PGPR) are considered promising bio-inoculants for poplar production, but their effects can vary depending on bacterial strain, host genotype, and growth environment. In this study, we evaluated the responses of ten poplar clones representing three taxonomic groups to five indigenous PGPR strains under greenhouse and open-field nursery conditions. Under greenhouse conditions, Priestia aryabhattai GJRr2, Variovorax boronicumulans HNRr1, and a mixed inoculum (Mix) showed the most consistent positive effects. Plant height increased from 86.1 ± 5.6 cm in the control to 156.0 ± 9.4 cm in the GJRr2 treatment, whereas HNRr1 produced the greatest stem diameter (9.01 ± 0.26 mm) and total fresh weight (94.0 ± 6.0 g). Clone identity explained a larger independent fraction of growth variation than bacterial strain, and the strongest integrated responses were observed in I-476, Dorskamp, and Eco28. Field responses were generally weaker, but GJRr2 and Mix still increased height, DBH, and stem volume, whereas ORa was associated with negative responses in these traits. These results demonstrate that PGPR effects in poplar are strain-specific, clone-dependent, and environmentally contingent, indicating that inoculant selection should account for both host genotype and performance stability across growth conditions. Full article

Biochemical markers of oxidative stress were used to evaluate the responses of poplar and willow clones grown in phytoremediation buffer plantations on landfill sites in Novi Sad and Vinča (near Belgrade), Serbia. The experiment was conducted using a randomized block design with three replications, each comprising blocks of nine plants arranged in a 3 × 3 layout, with ten leaves collected per block. Key parameters assessed included total phenolic content (TPC), total flavonoid content (TFC), ferric-reducing antioxidant power (FRAP), radical scavenging activity of DPPH (DPPH), and ABTS radical scavenging activity (ABTS). For the parameters FRAP, DPPH, and ABTS, higher values were recorded at the Novi Sad site, likely due to plants’ continuous groundwater access. The results indicate significant clone × site interaction for TPC, suggesting environment-specific clone responses for this parameter. There was a significant effect of clone on the variation in TPC, TFC, and FRAP, evidenced by the clear distinction in these parameters between poplar and willow clones, as poplar clones achieved higher values than willow clones. No significant effect of any of the examined sources of variation was found for the TFC/TPC ratio or FPR, and Pannonia was found to achieve significantly higher values compared to willow and clone 135/81. According to principal component analysis, the examined biochemical parameters were divided into three groups. Considering the results from the previous study of physiological and biomass parameters, DPPH and ABTS were included in the first group along with stomatal conductance (g_s), transpiration (E), and total biomass of the above-ground part (m_P), while TPC, TFC, and FRAP comprised the second group and FPR the third group. The first two principal components accounted for most of the variability, with the first PC clearly separating the interaction treatments of poplar and willow clones, and the second PC further distinguishing the treatments according to site. These findings underscore the difference between parameters regarding the effect of site and differences between clones. Further study of the significance of these parameters in selecting appropriate clones for phytoremediation on landfills, as well as on contaminated lands in general, is recommended. Full article

Megaplatypus mutatus, a major poplar pest in South America, tunnels into the xylem, weakening trunks and reducing wood quality. Volatile organic compounds (VOCs) are key mediators of plant–insect interactions and may reflect genotype-specific defence strategies. This study analysed VOC profiles of young and adult Populus deltoides cv. Harvard and P. × canadensis cv. Conti 12 under natural M. mutatus infestation. Gas chromatography–mass spectrometry putatively annotated 31 VOCs, including green leaf volatiles (GLVs), pentyl leaf volatiles (PLVs), terpenes, alcohols, aromatics and phenolics, 12 of which, to our knowledge, have not been previously reported in Populus VOC profiles. Harvard trees showed ~14.5-fold higher total VOC abundance than Conti trees. In Conti, constitutive VOC emissions remained stable regardless of infestation status or age. In contrast, under infestation, Harvard trees emitted10-fold higher constitutive VOCs than non-infested Harvard trees and ~52-fold higher than Conti, a pattern consistent with increased defensive activity. GLVs and PLVs relatively dominated both genotypes, although Harvard showed higher emissions. Terpenes were not detected in young Conti trees under our analytical conditions but were abundant and diverse in infested Harvard trees, which may indicate a stronger terpene-associated response in this clone. Several compounds were detected only under specific genotype–condition combinations in our dataset and therefore represent candidate volatiles for future behavioural and functional studies. These results are consistent with differences in VOC emission patterns between genotypes and age classes, improve our understanding of putative chemical cues in the interaction between Populus and M. mutatus, and provide a basis for future work towards sustainable pest management strategies. Full article

Specialized poplar plantations are relevant for wood-based panel production. In recent years, the Italian poplar sector has progressively moved towards more sustainable cultivation systems. Breeding programs developed new clones with fast growth and increased disease resistance. Agroforestry (AF) has emerged as a promising alternative to the conventional plantation (C), and its ecosystem services have been widely documented. This exploratory study compares the main physico-mechanical properties of solid wood from five new poplar clones cultivated in conventional and agroforestry plantation models. The peeling yields and the performances of plywood produced with their veneers are also investigated. Wood was obtained by harvesting seven-year-old trees in two experimental plantations located in the Veneto Region. All the clones were found to have a higher basic density than that of the ‘I-214’, the reference in the sector, and were suitable for veneers production. It was possible to obtain top-quality sheets from trees of both systems, with some differences between clones. However, the overall quality of the veneers depended on the type of clone and on the cultivation system, where conventional plantations provided better results. Higher mechanical performances were found in plywood produced from clones with higher density. The results provide knowledge to optimize agroforestry cultivation of poplar, also as a complementary source of timber supply for the concerned industrial sector. Full article

Signaling mediated by CLAVATA3/EMBRYO SURROUNDING REGION-RELATED (CLE) peptides and their receptors is essential for plants to adapt to abiotic stress. To address the global issue of drought-induced growth inhibition and mortality in poplar (Populus spp.), this study investigated the function of the PtrCLE1A gene from Populus trichocarpa Torr. et Gray in drought tolerance regulation. We employed gene cloning, expression vector construction, and genetic transformation of poplar, combined with bioinformatics analysis, subcellular localization, phenotypic observation, physiological index measurement, and gene expression analysis. The results demonstrated that both PtrCLE1A and PtrCLE1B encode pre-propeptides containing a signal peptide, with an identical mature peptide sequence (RLSPGGPDPRHH), and their putative receptors are PtrCLV1/2. Furthermore, the PtrCLE1A pre-propeptide was localized around the plasma membrane in tobacco (Nicotiana benthamiana Domin) mesophyll cells, consistent with its predicted function. PtrCLE1A and PtrCLE1B are primarily expressed in the roots and xylem of P. trichocarpa. Additionally, only the PtrCLE1A promoter contained drought-responsive cis-elements, and its expression was induced by drought stress in root, xylem, and leaf tissues of P. trichocarpa. Overexpression of the PtrCLE1A gene in Populus tomentosa Carrière (triploid) significantly increased adventitious root length under osmotic stress. Overexpression lines exhibited 22.00% to 22.92% longer adventitious roots than EV lines at 50/100 mM mannitol, and 65.12% to 73.17% longer at 150 mM mannitol. The OE lines also exhibited higher photosynthetic capacity and instantaneous water use efficiency (iWUE), along with reduced membrane damage under drought conditions, indicating enhanced drought resistance. This study provides new genetic resources and a theoretical foundation for molecular breeding of drought-tolerant poplar. Full article

Selenium-Binding Protein 1 (SBP1), involved in selenium metabolism, contributes to plant stress response. However, it is currently unknown whether the SBP1 protein from Liriodendron hybrid (LhSBP1) plays a role in response to cold stress. In this study, transgenic overexpression lines of LhSBP1 in Arabidopsis thaliana and Populus deltoides × P. euramericana cv. ‘Nanlin 895’, were used as materials to conduct phenotypic observations and physiological and biochemical determinations under cold stress. The results showed that the full-length CDS sequence of LhSBP1 gene was cloned, with a length of 1467 bp, encoding 488 amino acids. Under cold stress, physiological and biochemical indexes showed that the contents of reactive oxygen species (ROS) and malondialdehyde (MDA) in transgenic Arabidopsis were lower, with the contents of hydrogen peroxide (H₂O₂) and superoxide anion (O₂⁻) being 0.72 and 0.71 times those of the wild type, respectively, and the MDA content was 0.53 times that of the wild type. Compared with the wild type, the activities of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) increased by 1.2, 1.75, and 1.48 times respectively, and the soluble protein content increased by 1.41 times, which significantly improved the cold tolerance of Arabidopsis. The contents of H₂O₂, O₂⁻, and MDA in LhSBP1 transgenic ‘Nanlin 895’ poplar were 0.63 and 0.67 times and 0.6 times those of wild type, respectively. The activities of SOD, POD and CAT were increased by 1.37, 1.48, and 1.44 times, and the soluble protein was increased by 1.28 times, which significantly improved the cold tolerance of ‘Nanlin 895’ poplar. Taken together, this study utilized two model plant systems to demonstrate the positive and conserved functions of LhSBP1 in plant cold tolerance defense response, which provided valuable genetic resources for the breeding of cold-tolerance woody plants. Full article

Developing sustainable and eco-friendly approaches to plant propagation, development, and protection is a common goal for the scientific community. Plant cell culturing enables us to obtain plant clones and produce biomolecules under controlled conditions. The same principle can be applied to the harvesting of extracellular vesicles (EVs). These nanosized structures are key players in cell communication and stress response by carrying, protecting, and delivering important biomolecules. Raising interest in the scientific community, EVs have been successfully tested as nanocarriers for therapeutics and biotechnology. However, despite their potential, there remains a gap in research on scalable, reliable sources for EV production. Our goals were to optimize EV production and isolation from induced poplar callus cell lines (Populus tremula × P. alba) and load these with RNA to validate their functionality as nanocarriers. We were able to isolate 2.5 × 10¹⁰ EVs/g, highlighting the potential for these lines to be mass-produced. Furthermore, RNA loaded into EVs through electroporation was internalized into Botrytis cinerea hyphae, reassuring their potential in protecting and delivering cargo. Our findings contribute to EV characterization and demonstrate that RNA delivery through EV transport could be a safe and effective method for future EV-based technologies in plant protection. Full article

The aim of this research was to assess the sex-related responses to AgNPs stabilized with citrate (Cit) and glutathione (GSH), relative to silver ions supplied as AgNO₃ in black poplar (Populus nigra L.), a dioecious, woody model species. The impact of the AgNPs-cit-GSH on male and female clones was evaluated by measuring key parameters of oxidative stress. The results showed that exposure to nanosilver resulted in lower Ag accumulation and reduced MDA levels in both genders compared to AgNO₃. The female clone exhibited a dose-dependent response, characterized by an increase in dry weight (DW), along with a reduction in nutrient uptake, protein content, and ATPase activity, as well as an upregulation of glutathione-S-transferase (GST) activity compared to the control. The male clone displayed a specific treatment response. Exposure to AgNPs-cit-GSH caused a decrease in DW, water content, and nutrient uptake, accompanied by a rise in protein content as well as GST activity. In AgNO₃-treated male cells, the increase in Ag content and MDA levels corresponded to a decrease in DW and a rise in protein, Cu, and Ca content. These findings offer valuable insights into sexual dimorphism in dioecious woody plants, a topic that has been largely understudied yet is critical for sustainable resource management strategies. Full article

Drought responses in poplar are genotype-dependent, yet standardized metrics for quantifying drought tolerance remain scarce. Here, we employed logistic modeling of relative electrolyte leakage (REC) for the first time in poplar to derive clone-specific semi-lethal polyethylene glycol (PEG) concentrations (LC₅₀), transforming a traditional descriptive assay into a quantitative, high-throughput drought-injury metric. Six elite Populus cultivars were exposed to increasing PEG concentrations, and their REC curves were fitted using a logistic function (R² = 0.885−0.981). The derived semi-lethal PEG concentration (LC₅₀) ranged from 7.99% in ‘PZ1’ (drought-sensitive, SS) to 13.44% in ‘YX2’ (drought-tolerant, ST), enabling clear classification. Under 10% PEG stress, ST maintained leaf water content (LWC) at 73%, while SS dropped to 63%. Malondialdehyde (MDA) content doubled in SS (44.7 nmol·g⁻¹ FW) but increased by only 25% in ST (33.5 nmol·g⁻¹ FW). Gas exchange analysis revealed that SS exhibited approximately twice the reduction in net photosynthetic rate (Pn), transpiration rate (Tr), and stomatal conductance (Gs) compared to ST, with intercellular CO₂ accumulation (Ci) occurring only in SS—indicating both stomatal and non-stomatal limitations. Osmolyte profiling showed that SS accumulated large amounts of soluble sugars (Ss) (+128%) and proline (Pro) (+230%), whereas ST maintained stable soluble protein (Sp) levels and only moderately increased proline (+120%). Antioxidant capacity differed markedly: catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) activities increased by 5.6-, 1.8-, and 2.0-fold in ST, respectively, compared to 3.4-, 1.3-, and 1.7-fold in SS. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) of ten physiological traits explained 89% of the total variance (R²X = 0.954, Q² = 0.973), identifying POD, SOD, CAT, and Pro as the most discriminative variables (VIP > 1). This four-marker signature converts a conventional dose–response assay into a rapid, low-cost screening module that can be deployed in robotic phenotyping platforms. Specifically, the high-ranking genotype ‘YX2’ is recommended for immediate use in water-limited plantations and as a robust parent for next-generation dryland breeding programs. Full article

Through research on the effects of soil and meteorological factors on poplar wood properties, poplar clones with enhanced cold tolerance, drought resistance, and salt–alkali tolerance were selected for large-scale cultivation in the Western Songnen Plain, Northern China. We evaluated wood physical properties (basic density) and anatomical characteristics (annual ring width—RW, vessel number—CNO, vessel lumen area—LA) of 15-year-old Populus simonii × P. nigra, Populus alba × P. berolinensis, P. euramericana N3016 × P. ussuriensis, and Populus pseudo-cathayana × P. deltodides clones in the typical black soil area and saline–alkali land. The results showed that black soil region was more suitable for poplar growth, which was influenced by both soil and meteorological factors. Among soil factors, pH was the primary factor influencing the radial growth of poplar clones, exhibiting a negative correlation for all clones except P. alba × P. berolinensis. Furthermore, P. euramericana N3016 × P. ussuriensis was affected by organic carbon, while P. simonii × P. nigra and P. alba × P. berolinensis were more influenced by potassium. Among climatic factors, basic wood density, annual ring characteristics, and vessel structural parameters in all clones were primarily influenced by wind speed and sunshine, with air temperature having the least effect. Among the four clones, P. alba × P. berolinensis displayed better growth performance (higher RW) and basic wood density (0.29–0.41 g/cm³) at both sites, while P. simonii × P. nigra proved suitable for cold regions. Both clones showing dual adaptability to saline–alkali and black soil environments in Northeast China. Full article

The population size of black poplar (Populus nigra L.), once an important part of floodplain forests in the Czech Republic, has greatly declined due to human activity. In this study, we applied microsatellite (SSR) markers to identify species and assess genetic diversity, with the aim of supporting conservation of this endangered species. A total of 378 poplar trees were analyzed following field surveys. Five diagnostic SSR markers with species-specific alleles for P. deltoides Bartr. ex Marsh. enabled the identification of 39 interspecific hybrids, which were distinguished from native P. nigra. Thirteen SSR loci were used to evaluate genetic diversity among confirmed P. nigra individuals. The results revealed high genetic variation, with 66% of pairwise genotype comparisons differing at all loci. After excluding 45 genetically similar individuals, 292 genetically verified and polymorphic P. nigra trees were selected as potential sources of reproductive material. Genetic differentiation (Fst) was highest between P. nigra and P. deltoides (0.27), and lowest between reference Populus ×euroamericana clones and detected hybrid poplars (0.05) from natural localities. Distinct genetic structures were identified among P. nigra, P. deltoides, and hybrid individuals. These findings provide essential data for the protection, reproduction, and planting of black poplar. Full article

Poplar (Populus spp.) is a keystone commercial tree species in Northeast China, valued for its high economic returns. The genotype-by-environment (G × E) interaction critically governs its growth performance and ecological adaptability, which are pivotal for ensuring the long-term sustainability and economic viability of poplar plantations. In this study, the fibrous roots of the (P. simonii × P. nigra) × P. deltoides clone planted at three distinct sites, including Lishu (named SR1), Xinmin (named SR2), and Cuohai (named SR3), were used to perform transcriptome and metabolome. Comparative analysis revealed 6246, 3455, and 3854 differentially expressed genes (DEGs) in the SR1 vs. SR2, SR1 vs. SR3, and SR2 vs. SR3 comparisons, respectively. These DEGs were functionally enriched in pathways associated with antioxidant enzyme activity, stimulus response, plant hormone signal transduction pathways, and α-linolenic acid metabolism. Metabolomic analysis identified 106, 147, and 189 significantly differentially accumulated metabolites (DAMs) across the same comparisons, primarily linked to glutathione metabolism, butanoate metabolism, and pentose–glucuronate interconversions. Notably, we identified a core regulatory module comprising 57 genes and four key metabolites within the α-linolenic acid metabolic pathway, which exhibited strong correlations with phenotypic adaptability. These findings provide mechanistic insights into poplar’s plasticity under environmental heterogeneity, offering a molecular roadmap for future breeding strategies and the sustainable expansion of poplar cultivation. Full article

Poplar (Populus) clones are widely used for riparian afforestation owing to their fast growth and ecological benefits. However, selecting suitable clones for site-specific conditions remains a key challenge. In this study, we evaluated the survival and growth performance of nine poplar clones belonging to three hybrid groups—Populus deltoides (D), P. deltoides × P. nigra (DN), and P. nigra × P. suaveolens (NS)—at two riparian sites in Korea. Significant differences were observed in the survival, height, diameter, basal area, and basal area increment (BAI) among clones and between sites. DN hybrids exhibited superior overall performance in both survival and growth traits compared to D and NS clones. In the DN group, clones Eco-28, I-476, and Dorskamp consistently ranked highest in aggregate performance. Notably, I-476 and Eco-28 demonstrated both high productivity and stability across sites, as reflected in their low coefficients of variation (CVs). In contrast, Dorskamp, while highly productive, showed relatively high variability across environments. These findings highlight DN hybrids—particularly Eco-28 and I-476—as promising candidates for riparian afforestation, offering a balanced combination of high productivity and environmental stability. Full article