Search Results (63)

The distinctive leaf and twig heteromorphism in Euphrates poplar (Populus euphratica Oliv.) reflects its adaptive strategies to cope with arid environments across ontogenetic stages. In the key distribution area of P. euphratica forests in China, we sampled P. euphratica twigs (which grow in the current year) at different age classes (1-, 3-, 5-, 8-, and 11-year-old trees), then analyzed their morphological traits, biomass allocation, as well as allometric relationships. Results revealed significant ontogenetic shifts: seedlings prioritized vertical growth by lengthening stems (32.06 ± 10.28 cm in 1-year-olds) and increasing stem biomass allocation (0.36 ± 0.14 g), while subadult trees developed shorter stems (6.80 ± 2.42 cm in 11-year-olds) with increasesd petiole length (2.997 ± 0.63 cm) and lamina biomass (1.035 ± 0.406 g). Variance partitioning showed that 93%–99% of the trait variation originated from age and individual differences. Standardized major axis analysis demonstrated a consistent “diminishing returns” allometry in biomass allocation (lamina–stem slope = 0.737, lamina–petiole slope = 0.827), with age-modulated intercepts reflecting developmental adjustments. These patterns revealed an evolutionary trade-off strategy where subadult trees optimized photosynthetic efficiency through compact architecture and enhanced hydraulic safety, while seedlings prioritized vertical space occupation. Our findings revealed that heteromorphic twigs play a pivotal role in modular trait coordination, providing mechanistic insights into P. euphratica’s adaptation to extreme aridity throughout its lifespan. Full article

This study examined the bioproductivity of two poplar genotypes propagated by single-tree stem cuttings. The experiment compared variants using cuttings of different lengths (10–22 cm) and containers with volumes from 1 to 3 L. It was found that the best growth performance of seedlings in height according to the traditional container technology (70.6 ± 5.5–111.5 ± 5.0 cm) was observed in the intersectional hybrid of poplar ‘E.s.-38’ (genotype 1). The predominance of the genotype factor over the technology of rooting cuttings was established. The fast-growing genotype 1, E.s.-38, had higher productivity and plant height indices, suggesting it as a variety that can allow for the growth of standard planting material in containers in one season. For genotype 1, the length of cuttings was 10–14 cm when the container volume was increased to 3 L, which could increase the number of cuttings from one mother plant by 2–3 times. The revealed correlations between the height of the seedling and the diameter of the increment, as well as the analysis of the proportions of plant organs, showed that biological features of the rooting of stem cuttings depended on the genotype of poplars. The natural type G2 was characterized by the prevalence of root system growth over the growth of other organs; in the case of short cuttings, the proportion of leaves increased in plants to enhance photosynthesis and ensure rhizogenesis. Full article

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is an enzyme widely involved in glycolysis in animal cells and in non-metabolic processes, including apoptosis and the regulation of gene expression. GAPDH is a ubiquitous protein that plays a pivotal role in plant metabolism and handling of stress responses. However, its function in plant stress resistance remains unknown. Identification and systematic analysis of the GAPDH family in Populus deltoides (P. deltoides) have not been performed. Bioinformatics methods were used to analyze the physicochemical characteristics, structural characteristics, phylogenetic relationships, gene structure, motif analysis, and expression of GAPDH gene family members in P. deltoides. We identified 12 GAPDH members in P. deltoides. Five types of PdGAPDH were identified: GAPA, GAPB, GAPC1, GAPC2, and GAPCp. PdGAPDH genes were differentially expressed in leaves, stems, and roots of 1-year-old poplar seedlings. PdGAPDH gene transcripts showed that PdGAPDH2 and PdGAPDH4 were highly expressed in the leaves. In the roots, seven genes—PdGAPDH01, PdGAPDH05, PdGAPDH06, PdGAPDH07, PdGAPDH08, PdGAPDH09, and PdGAPDH12—showed significantly high expression levels. PdGAPDH02, PdGAPDH03, PdGAPDH04, and PdGAPDH11 showed decreased expression under drought conditions and recovered after re-watering. These results lay the foundation for further studies on the drought stress mechanisms of P. deltoides. Full article

Developing high-efficiency mixed forests or converting low-efficiency pure forests into near-natural mixed forests with optimal structure and function is a crucial aspect of forest management. In the initial stages of afforestation or stand improvement, fertilization and planting distance significantly influence the formation and development of mixed forests. This study investigated how nutrients and planting distance affect root competition between five-year-old Chinese pine (Pinus tabuliformis) and one-year-old Chinese white poplar (Populus tomentosa) and identified the factors influencing the competitive ability of these two species. Field planting experiments used three fertilization gradients (63 g·m⁻², 125 g·m⁻², and 250 g·m⁻²) of Stanley compound fertilizer with an N:P:K ratio of 2:1:1 and two planting distances (25 cm and 50 cm). Each experimental group was planted in circular plots with a radius of 0.5 m, yielding a total of nine plots. The effects of different fertilization concentrations and planting distances on root distribution were analyzed both horizontally and vertically. Pearson correlation analysis was used to assess the relationship between roots and soil nutrients, while Levins’ niche overlap formula evaluated the differences in root competition between the species. Furthermore, principal component analysis quantified the relationships between impact factors and the root competitiveness of the two species. Results indicated that both species primarily allocated their fine root biomass to the shallow 0–10 cm layer. Pinus tabuliformis primarily extended to the southwest, while Populus tomentosa predominantly grew to the north. Both species exhibited enhanced root growth at moderate nutrient concentrations of 125 g·m⁻². At a planting distance of 50 cm from Pinus tabuliformis, Populus tomentosa seedlings demonstrated superior root growth compared to those planted 25 cm apart. Pinus tabuliformis demonstrated greater competitive ability in the deeper 10–30 cm soil layers compared to Populus tomentosa, which showed the opposite pattern in the shallow 0–10 cm layers. Furthermore, available phosphorus (contribution rate of one impact factor on the competitiveness indexes, CR: −0.998), organic matter (CR: −0.978), total nitrogen (CR: −0.947), and alkali-hydrolysable nitrogen (CR: −0.937) significantly negatively impacted the competitiveness indexes of Pinus tabuliformis. The fine root surface area, volume, and length of Populus tomentosa also significantly negatively affected its competitiveness indexes, with all contribution rates exceeding an absolute value of 0.847. Results indicated that the root distributions of Pinus tabuliformis and Populus tomentosa overlapped spatially, with each species exhibiting advantages in different regions. Therefore, in future plantation reconstruction and forest management, it is essential to thoroughly evaluate root, soil, and fertilizer factors, adjusting planting distances accordingly, to effectively mitigate competition between the two species and successfully establish a mixed forest. Full article

Selecting seedlings of varying sizes and effectively managing root pruning are key challenges in transplantation. However, the effects of seedling size and root pruning on transplantation outcomes are not fully understood. This study classified one-year-old Populus ‘Beilinxiongzhu-01’ seedlings into three size categories based on height: large (308.75 ± 9.66 cm), medium (238.00 ± 7.71 cm), and small (138.92 ± 7.18 cm). In early March of the subsequent year, root pruning was applied with varying intensities based on root collar diameter: low (15 times), medium (7.5 times), and high (3.75 times). A control group without pruning was also included. Over the year, key phenological and morphological traits were monitored. The results showed that (1) root pruning significantly impacted the phenology of seedlings, accelerating root emergence, delaying early leaf phenology, increasing the dieback rate, and postponing end-of-season defoliation. Mortality and the rapid growth phase were not significantly affected. Larger seedlings exhibited earlier end-of-season defoliation and higher dieback rates early in the growing season, while smaller seedlings advanced in early leaf development. (2) Except under low or no pruning, root pruning reduced seedling height (H), diameter at breast height (DBH), and root collar diameter (RCD). However, across all treatments, these indicators remained higher in larger seedlings compared to smaller ones. Under medium- and high-intensity pruning, smaller seedlings exhibited higher relative growth rates and larger leaf areas than larger seedlings, with the reduction in these variables becoming more pronounced as seedlings increased in size. Notably, only larger seedlings demonstrated a reduction in maximum growth rate, suggesting greater vulnerability to root pruning. In summary, root pruning induced significant phenological and morphological differences across seedling sizes. While smaller seedlings showed some response to pruning, larger seedlings experienced more pronounced phenological disruptions and growth inhibition. Full article

Populus spp. is an economically valuable tree worldwide, known for its adaptability, fast growth, and versatile wood, often cultivated in short-rotation plantations. Effective propagation is crucial for rapid genetic improvement and global demand for forest products and biomass energy. This study focused on the rooting and growth of poplar cuttings, examining shoot collection timing and growth stimulant treatments across four hybrids: Populus deltoides × P. nigra (Agathe F), P. maximowiczii × P. trichocarpa (Arges), P. deltoides × P. trichocarpa (Donk), and an interspecific hybrid Populus × canadensis (F-448). The experiment used hybrid poplar cuttings collected in spring 2022 and 2023, planted in controlled climates with a randomized block design. Cuttings were soaked for 24 h in growth stimulants, namely indole-3-butyric acid, cinnamic acid, and indole-3-acetic acid. After 12 weeks, rooting percentage and seedling height were assessed. The study found that the optimal time for collecting poplar cuttings for best rooting is late winter to early spring, specifically from March to early April, with shoots collected after early April showing the lowest rooting potential. The growth stimulants significantly influenced the growth of poplar seedlings. There was a tendency for lower concentrations to increase root formation and seedling height, while higher concentrations had adverse effects. Despite variations in growth rates, a consistent growth pattern was observed across different shoot collection dates for all genomic groups. Full article

Transgenic technology is a potent tool for verifying gene functions, and poplar serves as a model system for genetically transforming perennial woody plants. However, the current poplar genetic transformation system is limited to a few genotypes. In this study, we developed an efficient transformation system based on the Agrobacterium-mediated transformation of Populus wulianensis, a rare and endangered tree species endemic to Shandong Province. Aseptic seedlings of P. wulianensis were used as experimental materials, and the optimal medium for inducing adventitious buds was explored as 1/2(NH₄NO₃) MS + 0.05 mg/L naphthalene acetic acid (NAA) + 0.5 mg/L 6-benzylaminopurine (6-BA), resulting in up to 35 adventitious buds. The selection resistance critical pressure of 300 mg/L for timentin can effectively inhibit the growth of Agrobacterium while promoting the induction of adventitious buds in leaves. The critical screening pressure for kanamycin for producing resistant adventitious buds and inducing resistant rooting seedlings was 100 mg/L. We optimized several independent factors, which significantly enhanced the efficiency of genetic transformation. The leaves were infected with Agrobacterium suspension diluted twice by adding 100 μmol/L acetylsyringone (β-AS) (OD₆₀₀ = 0.6) for 15 min, followed by co-culture in the dark for 3 d. Using this improved transformation system, we obtained transgenic P. wulianensis clones overexpressing the enhanced green fluorescent protein (EGFP) gene through direct organogenesis. Among the 112 resistant buds obtained, 17 developed resistant rooting in seedlings. Eight positive plants were identified through DNA, RNA, and protein level analyses, with a positivity rate of 47.06%. This study provides a foundation for developing and utilizing P. wulianensis germplasm resources and lays the groundwork for resource improvement. Full article

Populus deltoides Bartr. ex Marsh. represents a valuable genetic resource for fast-growing plantations in temperate regions. It holds significant cultivation and breeding potential in northern China. To establish an efficient breeding population of poplar, we studied the genetic variation of P. deltoides from different provenances. Our focus was on genotypes exhibiting high growth rates and efficient water and nutrient use efficiency (WUE and NUE). We evaluated 256 one-year-old seedlings from six provenances, measuring height, ground diameter, total biomass, and leaf carbon and nitrogen isotope abundance (δ¹³C and δ¹⁵N). Our analytical methods included variance analysis, multiple comparisons, mixed linear models, correlation analysis, and principal component analysis. The results showed that the coefficient of variation was highest for δ¹⁵N and lowest for δ¹³C among all traits. Except for δ¹⁵N, the effects of intra- and inter-provenance were highly significant (p < 0.01). The rates of variation for all traits ranged from 78.36% to 99.49% for intra-provenance and from 0.51% to 21.64% for inter-provenance. The heritability of all traits in AQ provenance was over 0.65, and all exhibited the highest level except for seedling height. All traits were significantly positively correlated with each other (p < 0.05), while ground diameter, total biomass, and WUE were highly significantly negatively correlated with latitude (p < 0.01). After a comprehensive evaluation, two provenances and eight genotypes were selected. The genetic gains for seedling height, ground diameter, total biomass, WUE, and NUE were 27.46 cm (178-2-106), 3.85 mm (178-2-141), 16.40 g (178-2-141), 0.852‰ (LA05-N15), and 3.145‰ (174-1-2), respectively. Overall, we revealed that the abundant genetic variation in P. deltoides populations mainly comes from intra-provenance differences and evaluated provenances and genotypes. The results of this study will contribute to optimizing and enhancing the breeding process of Chinese poplar and improving the productivity of fast-growing plantations. Full article

Poplar is a globally important industrial tree species due to its fast growth and abundant applications. However, poplars require sufficient water during the growing season, and drought usually limits their production. Drought caused by climate change poses a serious threat to widely planted poplar plantations, making it crucial to clarify and improve the drought resistance of poplars. We employed two male poplar clones, namely, Siyang-1 (Populus × euramericana ‘Siyang-1’) and NL3804 (Populus deltoides ‘Nanlin 3804’), to investigate the growth and physiological responses of these clones to soil drought stress within 25 days. Under drought treatment, both clones experienced a significant reduction in height growth and biomass accumulation, with Siyang-1 exhibiting a more substantial decrease. Under drought treatment, Siyang-1 allocated more assimilates to roots than NL3804. Compared with Siyang-1, NL3804 wilted earlier and had a significantly higher wilting coefficient (p < 0.05). Siyang-1 had higher peroxidase (POD) activity in leaves under drought stress, while NL3804 had a greater increase in membrane permeability. Drought stress increased P absorption and decreased K absorption in both clones but had no significant effect on N absorption. The translocation of limited N and K resources into the stems and roots, as well as the increased uptake of P by the roots, can contribute to defending against drought for poplars. Siyang-1 enhances its drought resistance by modulating its nutrient status and slowing its growth rate, whereas NL3804 accumulates more biomass in the drought stage but perishes sooner, due to imbalances in water and antioxidant systems. Full article

Improving the quality of tree planting material for carbon sequestration through reforestation can help solve environmental problems, including the need to reduce the concentration of carbon dioxide in the atmosphere. The purpose of this study was to investigate the possibility of using humic substances in combination with rhizosphere microorganisms Pseudomonas protegens DA1.2 and Pseudomonas sp. 4CH as a means to stimulate the growth of seedlings of pine, poplar, large-leaved linden, red oak, horse chestnut, and rowan. Humic substances stimulated the growth of shoots and roots of pine, large-leaved linden, and horse chestnut seedlings. The effects of bacteria depended on both plant and bacteria species: Pseudomonas protegens DA1.2 showed a higher stimulatory effect than Pseudomonas sp. 4CH on pine and linden, and Pseudomonas sp. 4CH was more effective in the case of chestnut. An additive effect of humates and Pseudomonas protegens DA1.2 on the growth rate of pine and linden saplings was discovered. Poplar, red oak, and rowan seedlings were unresponsive to the treatments. The growth-stimulating effects of the treatments are discussed in connection with the changes in carbon, chlorophyll, and nitrogen contents in plants. The results show the need for further research in bacterial species capable of stimulating the growth of plant species that were unresponsive in the present experiments. Full article

Knowledge of tree biomass allocation is fundamental for estimating forest acclimation and carbon stock for global changes in the future. Optimal partitioning theory (OPT) and allometric partitioning theory (APT) are two major patterns of biomass allocation, and occurrences have been tested on taxonomical, ontogenetic, geographic and environmental scales, showing conflicting results and unclear ecophysiological mechanisms. Here, we examine the biomass allocation patterns of two young poplar (Populus) clones varying greatly in drought resistance under different soil water and nitrogen availabilities and the major physiological processes involved in biomass partitioning. We found that Biyu, a drought-sensitive hybrid poplar clone, had significant relations among biomass of leaf, stem and root, showing allometric partitioning. Xiaoye, a drought-tolerant poplar clone native to semi-arid areas, on the contrary, showed tightly regulated biomass allocation following optimal partitioning theory. Biyu had higher nitrate reductase activity in the fine roots, while Xiaoye had higher nitrate reductase activity in the leaves. Biochemical analyses and measurements of fluorescence and gas exchange showed that Xiaoye maintained more stable chloroplast membranes and photosystem electron flow, showing higher water use efficiency and a higher resistance to drought. A nitrogen addition could improve leaf photosynthesis and growth both in Biyu and Xiaoye seedlings under drought conditions. We concluded that the two poplar clones showed different biomass allocation patterns and suggest that the site of nitrate assimilation may play a role in biomass partitioning under varying water and nitrogen availabilities. Full article

In the context of precision agriculture (PA), geomatic surveys exploiting UAV (unmanned aerial vehicle) platforms allow the dimensional characterization of trees. This paper focuses on the use of low-cost UAV photogrammetry to estimate tree height, as part of a project for the phytoremediation of contaminated soils. Two study areas with different characteristics in terms of mean tree height (5 m; 0.7 m) are chosen to test the procedure even in a challenging context. Three campaigns are performed in an olive grove (Area 1) at different flying altitudes (30 m, 40 m, and 50 m), and one UAV flight is available for Area 2 (42 m of altitude), where three species are present: oleander, lentisk, and poplar. The workflow involves the elaboration of the UAV point clouds through the SfM (structure from motion) approach, digital surface models (DSMs), vegetation filtering, and a GIS-based analysis to obtain canopy height models (CHMs) for height extraction based on a local maxima approach. UAV-derived heights are compared with in-field measurements, and promising results are obtained for Area 1, confirming the applicability of the procedure for tree height extraction, while the application in Area 2 (shorter tree seedlings) is more problematic. Full article

Near-surface O₃ has negative effects on plant productivity; however there were few studies on the effects of O₃ pollution on the belowground part of the ecosystem. The effect of O₃ stress on the belowground parts of poplar is unclear. We investigated the effects of O₃ pollution on poplar rhizosphere soil in open-top chambers (OTC). Two kinds of plants with different O₃ sensitivity were selected, i.e., high-sensitive poplar clone 546 and low-sensitive poplar clone 107. The control group and high-concentration O₃ group were set up: charcoal-filtered air, CF; unfiltered air + 60 ppb O₃, NF. Poplar rhizosphere soil was taken after 96 days (15 June to 17 September 2020) of cultivation in OTCs. O₃ stress decreased the amplicon sequence variations (ASVs) of microorganisms in poplar 107 and poplar 546 rhizosphere soil, with no significant interspecific difference. The effect of O₃ fumigation on the fungal community was greater than that on the bacterial community. The correlation between the bacterial community and rhizosphere soil physicochemical indices was closer than that of the fungal community. Some fungi, such as Clitopilus hobsonii, Mortierella sp., and Minimedusa, might help poplar resist the O₃ stress. O₃ stress had direct impacts on the pH, nutrients, and enzyme activities of rhizosphere soil, while it had indirect negative impacts on microbial community composition by nutrients. There was no difference in sensitivity between rhizosphere soil response to O₃ stress of poplar clone 107 and clone 546, which might take a longer accumulation time to show the effect. This study provides a certain basis for accurately evaluating the ecological effects of O₃ pollution. Full article

Poplar (Populus spp.) is a valuable tree species with multiple applications in afforestation. However, its growth in saline areas, including coastal regions, is limited. This study aimed to investigate the physiological mechanisms of arbuscular mycorrhizal fungi (AMF) symbiosis with 84K (P. alba × P. tremula var. glandulosa) poplar under salt stress. We conducted pot experiments using NaCl solutions of 0 mM (control), 100 mM (moderate stress), and 200 mM (severe stress) and evaluated the colonization of AMF and various physiological parameters of plants, including photosynthesis, biomass, antioxidant enzyme activity, nutrients, and ion concentration. Partial least squares path modeling (PLS-PM) was employed to elucidate how AMF can improve salt tolerance in poplar. The results demonstrated that AMF successfully colonized the roots of plants under salt stress, effectively alleviated water loss by increasing the transpiration rate, and significantly enhanced the biomass of poplar seedlings. Mycorrhiza reduced proline and malondialdehyde accumulation while enhancing the activity of antioxidant enzymes, thus improving plasma membrane stability. Additionally, AMF mitigated Na⁺ accumulation in plants, contributing to the maintenance of a favorable ion balance. These findings highlight the effectiveness of using suitable AMF to improve conditions for economically significant tree species in salt-affected areas, thereby promoting their utilization. Full article

Magnetic fields play an important role in regulating plant growth and development, especially in improving plant stress tolerance. However, the physiological mechanism underlying the magnetic effects is still unclear. Here, we examined changes in reactive oxygen species (ROS) levels and ion flux in poplar (Populus × deltoides ‘Lulin-2’) seedling roots under salt stress in a static magnetic field (SMF). SMF treatment significantly increased seedling growth and mitigated the effects of salt stress on root growth. Furthermore, SMF treatment activated ROS and calcium signals in poplar roots. Relative to the SMF treatment group, control plants had significantly higher levels of cytoplasmic free Ca²⁺ ([Ca²⁺]_cyt) and ROS following exposure to high salt concentrations. Under salt conditions, SMF treatment reduced increases in Na⁺ concentrations and maintained stable K⁺ and Ca²⁺ concentrations and K⁺/Na⁺ and Ca²⁺/Na⁺ ratios. NMT analysis suggests that SMF treatment may drive cation effluxes in poplar seedling roots. Susceptibility tests of Na⁺-transport inhibitors indicated that SMF treatment contributed to Na⁺ repulsion and H⁺ uptake under salt stress. Moreover, SMF exposure allowed roots to retain the ability to reduce salt-induced K⁺ and Ca²⁺ root effluxes, and qRT-PCR results demonstrate that SMF treatment can increase the expression of stress-responsive genes such as PtrRBOHF, PtrNHX1 and PtrHA5 in poplar seedlings. Therefore, we conclude that treating poplar seedlings with SMF can help them establish a stable tolerance to salt stress by regulating ROS, [Ca²⁺]_cyt, and their regulatory networks. This study examined the physiological responses of poplar to SMF exposure under salt stress, providing insights into plant magnetobiological effects. Full article