Search Results (878)

Climate extremes threaten the resilience of Eucalyptus plantations, yet hybridization with drought-tolerant species may enhance stress tolerance. This study analyzed xylem anatomical and functional drought responses in commercial Eucalyptus grandis (GG) clones and hybrids: E. grandis × camaldulensis (GC), E. grandis × tereticornis (GT), and E. grandis × urophylla (GU1, GU2). We evaluated vessel traits (water transport), fibers (mechanical support), and wood density (D) in stems and branches. Theoretical stem hydraulic conductivity (k_Stheo), vessel lumen fraction (F), vessel composition (S), and associations with previous hydraulic and growth data were assessed. While general drought responses occurred, GC had the most distinct xylem profile. This may explain it having the highest performance in different irrigation conditions. Red gum hybrids (GC, GT) maintained k_Stheo under drought, with stable F and a narrower vessel size, especially in branches. Conversely, GG and GU2 reduced F and S; and stem k_Stheo declined for a similar F in these clones, indicating vascular reconfiguration aligning the stem with the branch xylem. Almost all clones increased D under drought in any organ, with the highest increase in red gum hybrids. These results reveal diverse anatomical adjustments to drought among clones, partially explaining their growth responses. Full article

Deadwood is essential for the forest ecosystem productivity and stability. A growing body of evidence indicates that deadwood-inhabiting microbes are effective decomposition agents, yet little is known about how changes in microbial communities during the initial deadwood decay. In a small forest area, we performed dense sampling from the top, middle, and bottom portions of two representative Pinus massoniana cultivars logs to track deadwood xylem microbiota shift during the initial deadwood decay. We found xylem mycobiota varied dramatically during the initial deadwood decay. Deadwood microbes might largely originate from the endophytic microbes of living trees during the initial deadwood decay. Notably, bark type is an important driving factor for xylem mycobiota changes during the initial deadwood decay. Ten upregulated metabolites were screened out by a univariate analysis approach. Moreover, our correlation analysis suggests that enriched microbes at class level was significantly correlated with the upregulated metabolites during the initial deadwood decay. Our work provides new insights into the process of mycobiota and metabolite changes during the initial deadwood decay. Full article

The bZIP gene family play a crucial role in plant growth, development, and stress responses, functioning as transcription factors. While this gene family has been studied in several plant species, its roles in the endangered woody plant Phoebe bournei remain largely unclear. This study comprehensively analyzed the PbbZIP gene family in P. bournei, identifying 71 PbbZIP genes distributed across all 12 chromosomes. The amino acid count in these genes ranged from 74 to 839, with molecular weights varying from 8813.28 Da to 88,864.94 Da. Phylogenetic analysis categorized the PbbZIP genes into 12 subfamilies (A-K, S). Interspecific collinearity analysis revealed homologous PbbZIP genes between P. bournei and Arabidopsis thaliana. A promoter cis-acting element analysis indicated that PbbZIP genes contain various elements responsive to plant hormones, stress signals, and light. Additionally, expression analysis of public RNA-seq data showed that PbbZIP genes are distributed across multiple tissues, exhibiting distinct expression patterns specific to root bark, root xylem, stem bark, stem xylem, and leaves. We also performed qRT-PCR analysis on five representative PbbZIP genes (PbbZIP14, PbbZIP26, PbbZIP32, PbbZIP67, and PbbZIP69). The results demonstrated significant differences in the expression of PbbZIP genes under various abiotic stress conditions, including salt stress, heat, and drought. Notably, PbbZIP67 and PbbZIP69 exhibited robust responses under salt or heat stress conditions. This study confirmed the roles of the PbbZIP gene family in responding to various abiotic stresses, thereby providing insights into its functions in plant growth, development, and stress adaptation. The findings lay a foundation for future research on breeding and enhancing stress resistance in P. bournei. Full article

Background: Catalpa bungei ‘Jinsi’ has excellent wood properties and golden texture, which is widely used in producing furniture and crafts. The lignin content and structural composition often determine the use and value of wood. Hence, investigating the characteristics of the annual dynamics of lignin anabolic metabolites in C. bungei ‘Jinsi’ and analyzing their synthesis pathways are particularly important. Methods: We carried out targeted metabolomics analysis of lignin synthesis metabolites using ultra-performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS) on the xylem samples of C. bungei ‘Jinsi’ in February, April, July, October 2022, and January 2023. Results: A total of 10 lignin synthesis–related metabolites were detected: L-phenylalanine, cinnamic acid, p-coumaraldehyde, sinapic acid, p-coumaric acid, coniferaldehyde, ferulic acid, sinapaldehyde, caffeic acid, and sinapyl alcohol (annual total content from high to low). These metabolites were mainly annotated to the synthesis of secondary metabolites and phenylpropane biosynthesis. The annual total content of the 10 metabolites showed the tendency of “decreasing, then increasing, and then decreasing”. Conclusions: C. bungei ‘Jinsi’ is a typical G/S-lignin tree species, and the synthesis of G-lignin occurs earlier than that of S-lignin. The total metabolite content decreased rapidly, and the lignin anabolism process was active from April to July; the metabolites were accumulated, and the lignin anabolism process slowed down from July to October; the total metabolite content remained basically unchanged, and lignin synthesis slowed down or stagnated from October to January of the following year. This reveals the annual dynamic pattern of lignin biosynthesis, which contributes to improving the wood quality and yield of C. bungei ‘Jinsi’ and provides a theoretical basis for its targeted breeding. Full article

Soil salinization, affecting approximately 954 million hectares globally, severely impairs plant growth and agricultural productivity. Apocynum venetum L., a perennial herbaceous plant with ecological and economic value, demonstrates remarkable tolerance to saline and alkali soils. This study investigated the effects of saline (NaCl) and alkali (Na₂CO₃ and NaHCO₃) stress on the growth, anatomical adaptations, and metabolite accumulation of A. venetum (Apocynum venetum L.). Results showed that alkali stress (100 mM Na₂CO₃ and 50 mM NaHCO₃) inhibited growth more than saline stress (NaCl 240 mM), reducing plant height by 29.36%. Anatomical adaptations included a 40.32% increase in the root cortex-to-diameter ratio (100 mM Na₂CO₃ and 50 mM NaHCO₃), a 101.52% enlargement of xylem vessel diameter (NaCl 240 mM), and a 68.69% thickening of phloem fiber walls in the stem (NaCl 240 mM), enhancing water absorption, salt exclusion, and structural support. Additionally, leaf palisade tissue densification (44.68% increase at NaCl 160 mM), along with epidermal and wax layer adjustments, balanced photosynthesis and water efficiency. Metabolic responses varied with stress conditions. Root soluble sugar content increased 49.28% at NaCl 160 mM. Flavonoid accumulation in roots increased 53.58% at Na₂CO₃ 100 mM and NaHCO₃ 50 mM, enhancing antioxidant defense. However, chlorophyll content and photosynthetic efficiency declined with increasing stress intensity. This study emphasizes the coordinated adaptations of A. venetum, providing valuable insights for the development of salt-tolerant crops. Full article

Calcium (Ca²⁺) is a macronutrient essential for the growth, development, yield, and quality of vegetables and fruits. It performs structural, enzymatic, and signaling functions in plants. This review examines Ca²⁺ translocation from soil to the fruit via the plant xylem network, emphasizing the importance of Ca²⁺ compartmentalization within fruit cell organelles in the development of calcium deficiency disorders such as blossom-end rot (BER). The underlying causes of BER and potential control measures are also discussed. Soil-available Ca²⁺, transported by water flow, enters the root apoplast through membrane channels and moves toward the xylem via apoplastic or symplastic routes. The transpiration force and the growth of organs determine the movement of Ca²⁺-containing xylem sap to aerial plant parts, including fruits. At the fruit level, the final step of Ca²⁺ regulation is intracellular partitioning among organelles and cellular compartments. This distribution ultimately determines the fruit’s susceptibility to Ca²⁺-deficiency disorders such as BER. Excessive sequestration of Ca²⁺ into organelles such as vacuoles may deplete cytosolic and apoplastic Ca²⁺ pools, compromising membrane integrity and leading to BER, even when overall Ca²⁺ levels are adequate at the blossom end. Effective BER management requires cultural and physiological practices that promote Ca²⁺ uptake, translocation to the fruit, and appropriate intracellular distribution. Additionally, the use of BER-resistant and Ca²⁺-efficient cultivars can help mitigate this disorder. Therefore, a comprehensive understanding of Ca²⁺ dynamics in plants is critical for managing BER, minimizing production loss and environmental impacts, and maximizing overall crop productivity. Full article

Rubber tree (Hevea brasiliensis Muell. Arg.) is a major tropical cash crop in southern China, with Hainan and Yunnan provinces being the main planting areas. In July 2023, bark cracking and gumming were observed on the trunks of mature rubber trees in Haikou City, Hainan Province, leading to xylem rot, which severely impacted the healthy growth of the rubber trees. The present study was conducted to confirm the pathogenicity of the patho-gen associated with stem gummosis disease, characterize it using morphological and mo-lecular tools, and devise field management strategies. Pathogenicity testing showed that this strain induced symptoms similar to those of natural outdoor infestation. Based on morphological study and molecular analyses of internal transcribed spacer (ITS), transla-tion elongation factor 1 alpha (TEF1-α), and β-tubulin 2 (TUB2) sequences, the causal agent was identified as Lasiodiplodia theobromae. Field trials demonstrated that an inte-grated fungicide approach—combining trunk application of Bordeaux mixture with root irrigation using citric acid–copper 6.4% + chelated copper-ammonium 15% at both 0.1% and 0.2% concentration—effectively suppressed stem gummosis disease incidence in rub-ber trees. To the best of our knowledge, this is the first report of L. theobromae causing stem gummosis on rubber tree in China. The findings of this study can provide valuable infor-mation for the management strategies and understanding of this disease. Full article

Vegetation growth is influenced not only by current climatic conditions but also by growth-enhancing signals and preceding climate factors. Taking the dominant species, Juniperus seravschanica Kom, in Tajikistan as the research subject, this study combines tree-ring width data with early xylem growth season data (from the start of xylem growth to the first day of the NDVI peak month), simulated using the Vaganov–Shashkin (V-S) model, a process-based tree-ring growth model. This study aims to explore the effects of vegetation growth carryover (VGC) and lagged climatic effects (LCE) on tree rings and the early xylem growth season at two different scales by integrating tree-ring width data and xylem phenology simulations. A vector autoregression (VAR) model was employed to analyze the response intensity and duration of VGC and LCE. The results show that the VGC response intensity in the early xylem growth season is higher than that of tree-ring width. The LCE duration for both the early xylem growth season and tree-ring width ranges from 0 to 11 (years or seasons), with peak LCE response intensity observed at a lag of 2–3 (years or seasons). The persistence of the climate lag effect on vegetation growth has been underestimated, supporting the use of a lag of 0–3 (years or seasons) to study the long-term impacts of climate. The influence of VGC on vegetation growth is significantly stronger than that of LCEs; ultimately indicating that J. seravschanica adapts to harsh environments by modulating its growth strategy through VGC and LCE. Investigating the VGC and LCE of multi-scale xylem growth indicators enhances our understanding of forest ecosystem dynamics. Full article

Climate models forecast warmer winter conditions, which could lead to an earlier spring xylem phenology in trees. Localized stem heat experiments mimic this situation and have shown that stem warming leads to an earlier cambial resumption in evergreen conifers. However, there are still few comprehensive studies comparing the responses to stem heating in coexisting conifers and hardwoods, particularly in drought-prone regions where temperatures are rising. We addressed this issue by comparing the responses (xylem phenology, wood anatomy, growth, and sapwood concentrations of non-structural carbohydrates—NSCs) of two pines (the Eurosiberian Pinus sylvestris L., and the Mediterranean Pinus pinaster Ait.) and a ring-porous oak (Quercus pyrenaica Willd.) to stem heating. We used the Vaganov-Shashkin growth model (VS model) to simulate growth phenology considering several emission scenarios and warming rates. Stem heating in winter advanced cambial phenology in P. pinaster and Q. pyrenaica and enhanced radial growth of the three species 1–2 years after the treatment, but reduced the transversal lumen area of earlywood conduits. P. sylvestris showed a rapid and high growth enhancement, whereas the oak responded with a 1-year delay. Heated P. pinaster and Q. pyrenaica trees showed lower sapwood starch concentrations than non-heated trees. These results partially agree with projections of the VS model, which forecasts earlier growth onset, particularly in P. pinaster, as climate warms. Climate-growth correlations show that growth may be enhanced by warm conditions in late winter but also reduced if this is followed by dry-warm growing seasons. Therefore, forecasted advancements of xylem onset in spring in response to warmer winters may not necessarily translate into enhanced growth if warming reduces the hydraulic conductivity and growing seasons become drier. Full article

Grapevine (Vitis vinifera) is a key crop in Mediterranean agriculture, now increasingly threatened by Xylella fastidiosa subsp. Fastidiosa (Xff), the causal agent of Pierce’s disease. This study investigated: (1) the diversity of culturable fungal endophytes in the xylem sap of naturally Xff-infected grapevines, and (2) the interaction between Xff and the pathogenic fungus Sclerotinia sclerotiorum identified in the sap. The xylem sap was collected from Cabernet Sauvignon vines in Mallorca, Spain, and fungal communities were characterized using culture-dependent methods. Both beneficial fungi (e.g., Aureobasidium pullulans, Rhodotorula mucilaginosa) and pathogenic species (e.g., S. sclerotiorum, Cladosporium sp., Alternaria alternata, and the Phoma complex) were isolated from both Xff-positive and Xff-negative plants, indicating similar community profiles. Although limited by small sample size, these findings offer preliminary evidence of complex ecological interactions between Xff and the xylem-associated mycobiota, with potential implications for grapevine health and disease development under varying environmental and management conditions. Further experiments under controlled conditions revealed that grapevines co-inoculated with Xff and S. sclerotiorum showed increased disease severity, suggesting a synergistic interaction. These preliminary results highlight the complex interplay between Xff and the fungal endophytic microbiome, which may modulate grapevine susceptibility depending on environmental and management conditions. Full article

Wood is an important raw material for industrial applications. Its fiber-specific genetic modification provides an effective strategy to alter wood characteristics in tree breeding. Here, we performed a cross-analysis of previously reported single-cell RNA sequencing and the AspWood database during wood formation to identify potential xylem fiber-dominant expressing genes in poplar. As a result, 32 candidate genes were obtained, and subsequently, we further examined the expression of these genes in fibers and/or vessels of stem secondary xylem using the laser capture microdissection technique and RT-qPCR. Analysis identified nine candidate genes, including PtrFLA12-2, PtrIRX12, PtrFLA12-6, PtrMYB52, PtrMYB103, PtrMAP70, PtrLRR-1, PtrKIFC2-3, and PtrNAC12. Next, we cloned the promoter regions of the nine candidate genes and created promoter::GUS transgenic poplars. Histochemical GUS staining was used to investigate the tissue expression activities of these gene promoters in transgenic poplars. In one month, transgenic plantlets grown in medium showed intensive GUS staining signals that were visible in the leaves and apical buds, suggesting substantial expression activities of these gene promoters in plantlets predominantly undergoing primary growth. In contrast, for three-month-old transgenic poplars in the greenhouse with predominantly developed secondary stem tissues, the promoters of seven of nine candidate genes, including PtrMYB103, PtrIRX12, and PtrMAP70, showed secondary xylem fiber-dominant GUS signals with considerable spatial specificity. Overall, this study presents xylem fiber-dominant promoters that are well-suited for specifically expressing genes of interest in wood fibers for forest tree breeding. Full article

Plant-specific WUSCHEL (WUS)-related homeobox (WOX) family of transcription factors are involved in apical meristem maintenance, embryogenesis, lateral organ development, and hormone signaling. Among the members of this family, WOX1 is known to play essential roles in many species. However, the function of the peony ‘Feng Dan’ (Paeonia ostii L.) WOX1 (PoWOX1) remains unknown. The initial bioinformatic analysis revealed that PoWOX1 belongs to the modern clade of the WOX gene family and has a highly conserved homeodomain (HD), the WUS motif, the STF-box, and the MAEWEST/WOX4-box. Subsequent heterologous overexpression in Arabidopsis thaliana revealed that PoWOX1 promotes root growth, early shoot initiation, and flowering. The root vascular tissues, especially the arrangement and size of xylem cells, were different between the PoWOX1-overexpressing transgenics and the wild-type plants, and the pericycle cells adjacent to the xylem divided more easily in the transgenics than in the wild type. Furthermore, under in vitro conditions, the transgenic leaf explants exhibited more callus induction and differentiation than the wild-type leaf explants. Thus, the study’s findings provide novel insights into the role of PoWOX1 in promoting root development and callus tissue induction and differentiation, serving as a reference for developing an efficient regeneration system for the peony. Full article

In this study, cucumber seedlings were treated with Scenedesmus obliquus at different concentrations (0.25, 0.50, 0.75, 1 g·L⁻¹) under saline–alkali stress (60 mM and 90 mM). The effects of Scenedesmus obliquus on the repair of cucumber seedlings under saline–alkali stress were explored from physiological and morphological perspectives by measuring growth physiological indices and observing microstructure. It provides a cytological basis for the development of microalgae biofertilizer. The results showed that the addition of Scenedesmus obliquus effectively alleviated the physiological and structural damage in cucumber seedlings caused by saline–alkali stress, with the best mitigation effect at 0.75 g·L⁻¹. More specifically, the addition of Scenedesmus obliquus significantly improved seedling fresh weight and plant height under saline–alkali stress, increased stem vascular vessel diameter, thickened vessel walls, reduced structural damage, the structural recovery of mitochondria, nuclei, and other organelles in the phloem; The results showed that root xylem vessel distribution became more centralized, vessel diameter decreased, and wall thickness decreased, with other changes similar to those in the stem; The number and volume of mesophyll cells increased, chloroplast morphology recovered, and chlorophyll content rose, effectively alleviating the impact of saline–alkali stress on photosynthesis. MDA content decreased, mitigating oxidative damage caused by saline–alkali stress. Full article

To understand the mechanisms underlying species assemblage along salt gradients in intertidal zones, we measured the xylem hydraulic vulnerability curves (HVCs), leaf water potential (ψ), stomatal conductance (g_s), specific leaf area (SLA), and wood density (WD) for six mangrove species of Avicennia marina, Bruguiera gymnorrhiza, Aegiceras corniculatum, Kandelia obovata, Sonneratia apetala, and Sonneratia caseolaris. We found the following: (1) A. marina and B. gymnorhiza had the most negative P₅₀ (water potential at which 50% of hydraulic conductivity was lost), while S. caseolaris and S. apetala had the least negative P₅₀, indicating different resistance to embolism in xylem; (2) P₅₀ and P₈₈ (water potential at which 88% of hydraulic conductivity was lost) declined with increasing salinity from the onshore to offshore species, as their water regulation strategy meanwhile transitioned from isohydry to anisohydry; (3) B. gymnorhiza had smaller SLA but larger hydraulic safety margin (HSM), implying potentially higher capacity of water retention in leaves and lower risk of hydraulic failure in xylem. These results suggest that hydraulic traits play an important role in shaping the salt-driven niche segregation of mangroves along intertidal zones. Our research contributes to a more comprehensive understanding of the hydraulic physiology of mangroves in salt adaption and may facilitate a general modeling framework for examining and predicting mangrove resilience to a changing climate. Full article

Lead (Pb) contamination in Moso bamboo forests poses a challenge in terms of sustainable development and raises concerns about the safety of bamboo shoots for consumption. However, the physiological impacts of Pb stress on Moso bamboo growth and the molecular mechanisms governing its adaptive responses remain poorly understood. This study comprehensively investigated the physiological and transcriptomic responses of Moso bamboo to Pb stress. The results showed that low concentrations (1–10 µM) of Pb stress had minimal adverse effects on biomass accumulation and the photochemical quantum yield of PSII in Moso bamboo. However, at a high Pb concentration (50 µM), the growth of roots was significantly inhibited, while Pb accumulation in the roots and shoots reached 15,611 mg·kg⁻¹ and 759 mg·kg⁻¹, respectively. The uptake of Pb was increased as the external Pb concentration increased, but the xylem loading of Pb reached saturation at 57.79 µM after six-hour exposure. Pb was mainly localized in the epidermis and pericycle cells in the roots, where the thickening of cell walls in these cells was found after Pb treatment. Transcriptomic profiling identified 1485 differentially expressed genes (DEGs), with significant alterations in genes associated with metal cation transporters and cell wall synthesis. These findings collectively indicate that Moso bamboo is a Pb-tolerant plant, characterized by a high accumulation capacity and efficient xylem loading. The tolerance mechanism likely involves the transcriptional regulation of genes related to heavy metal transport and cell wall biosynthesis. Full article