Trees最新文献

The macaw palm (Acrocomia spp.) stands out as a promising species for the sustainable production of vegetable oil due to its wide adaptability and potential use in multiple production chains. This study evaluated 11 genotypes, including parental genotypes and F₁ hybrids, for fruit biometric traits and mesocarp oil content, aiming to identify individuals with greater potential for genetic improvement programs. Analyses were carried out in plant material belonging to the Active Germplasm Bank of Macaw palm of the Federal University of Viçosa. The variables were subjected to analyses of variance, phenotypic correlation, and genetic diversity based on Mahalanobis generalized distance and the Tocher and UPGMA clustering methods. A broad phenotypic and genetic variability was observed among genotypes. Individual A4 exhibited larger fruits with higher mass and a greater pulp yield index, whereas the parent 47 − 1 showed the highest mesocarp oil content (55.31%). High heritability estimates (h² > 50%) and genetic accuracies confirmed the predominance of genetic over environmental effects. The clustering methods revealed three major genetic groups, reflecting the existing intra- and interspecific diversity. The results indicate a high potential for selection gains and reinforce the importance of biometric characterization of fruits and characterization of oil content to identify superior macaw palm genotypes aimed at expanding cultivation and promoting sustainable agro-industrial utilization.

Global warming intensifies high-temperature stress, threatening the growth and heartwood formation of Santalum album L. To elucidate the molecular basis of the heat-stress response, we conducted transcriptomic and metabolomic analyses on sandalwood seedlings under heat stress. Results showed: (1) Transcriptome identified 2,501 and 866 differentially expressed genes (DEGs) in TR0 vs. TR1 and TR1 vs. TR2 respectively (TD stands for metabolome samples, TR stands for transcriptome samples; suffix numbers correspond to sampling time points: 0 = day 0 before stress, 1 = day 1 of stress, 2 = day 3 of stress), mainly involving pathways such as plant hormone signal transduction, endoplasmic reticulum protein processing, heat shock protein regulation, and reactive oxygen species (ROS) clearance; (2) 26,244 and 20,451 metabolic ion features were detected in the positive and negative ion modes (PI and NI), respectively. The number of differentially expressed metabolites (DEMs) increased with stress time, and key metabolites of phenylpropanoid pathway such as 4-Hydroxycinnamic acid changed significantly. (3) Integrated analysis indicated that phenylpropanoid biosynthesis pathway was core response pathway, with high expression of key enzyme genes (PAL, C4H, 4CL). Expression level of the CHS gene (SA08G01315) in the flavonoid branch was significantly induced, which may be involved in antioxidant defense under heat stress. In the lignin branch, HCT transcript levels increased while COMT decreased sharply—a shift potentially linked to the wilting phenotype on day 3. Crucial enzyme genes like CAD were also highly expressed, indicating enhanced lignin monomer biosynthesis potential. Transcription factors (TFs) including ERF and MYB participated in pathway regulation. This study identified candidate key pathways and genes associated with the heat stress response in sandalwood, providing scientific evidence for subsequent variety improvement, domestication, and mechanistic research on plant thermal adaptation.

Key Message

Resin extraction modifies xylogenesis dynamics while maintaining annual xylem increment, inducing anatomical adjustments associated with hydraulically safer xylem traits. Traditional tapping appeared to provide the most balanced trade-off between resin yield and wood formation.

Abstract

Resin extraction in maritime pine (Pinus pinaster Aiton) constitutes a metabolic sink that theoretically competes with cambial activity for carbon resources. To mitigate potential wood formation impacts, shortened tapping periods are often proposed, yet their physiological effect remains unclear. This study investigated the impact of Traditional (March–October) versus Shortened (June–October) resin tapping regimes on annual radial increment, xylogenesis kinetics, and wood anatomy in a stand in central Portugal. Resin extraction did not reduce annual tree-ring width or total tracheid production compared to untapped Control trees. However, tapping altered the phenology of wood formation. While Control trees exhibited a typical Mediterranean bimodal growth pattern with a summer quiescence, tapped trees shifted to a continuous, prolonged period of wood formation, maintaining cambial activity into summer and late autumn to compensate for lower daily cell production rates. Anatomically, resin-tapped trees developed xylem characterized by narrower lumens and thicker cell walls, suggesting possible structural adjustments in xylem formation that may be associated with hydraulic function. The Shortened regime was not associated with clear advantages in resin production or wood formation dynamics. The Traditional method appeared to be the best silviculture option for co-production under the conditions evaluated in this study, with P. pinaster demonstrating sufficient plasticity to sustain both secondary growth and defense through temporal and anatomical adjustments.

Main conclusion

Seven LkMIR396 precursor genes were identified in Larix kaempferi, and their developmental and hormone responsive expression patterns suggest potential involvement in somatic embryogenesis.

Abstract

MicroRNA396 (miR396) is a highly conserved small RNA that regulates plant growth and development by targeting GROWTH-REGULATING FACTOR (GRF) transcription factors. However, its functions in gymnosperms, particularly conifers, remain poorly understood. In this study, seven precursor genes of LkMIR396 were cloned and identified from Larix kaempferi, all of which form typical stem-loop structures and produce three distinct mature Lk-miR396 sequences. The LkMIR396 family exhibited rapid and differential responses to exogenous hormones in embryogenic cell masses, with jasmonic acid (JA) strongly suppressing expression of all members. Heterologous overexpression of Lkpre-MIR396b1 in Arabidopsis thaliana significantly reduced rosette leaf area, length, and width accompanied by reduced expression of several predicted AtGRF targets. This effect may be achieved by attenuation of cytokinin (CK) signaling and activation of the JA pathway, as revealed by integrated transcriptome and metabolome analysis. During somatic embryogenesis, LkMIR396 family members showed low expression levels at early stages and a significant increase during the cotyledon stage (21–28 days), suggesting a potential association in cotyledon development. These results support the functional compatibility and possible conservation of the miR396–GRF regulatory module across seed plants. However, the direct functions of LkMIR396 during L. kaempferi somatic embryogenesis remain to be experimentally validated. This study provides a foundation for understanding the evolution and potential developmental functions of the miR396 family in conifers and identifies candidate regulatory relationships for future functional investigation.

Key Message

Post-wildfire salvage logging did not significantly impact the physiological recovery of resprouts in four evergreen hardwood tree species, suggesting salvage logging can be an effective post-fire management practice in mixed evergreen forests.

Abstract

Wildfires are threatening forest recovery worldwide due to climate change driven increases in severity and frequency. An important consideration for recovery is the post-fire land management practices, such as salvage logging, which can act as a secondary disturbance in forest communities. While much research has been done on certain forest types following wildfire and salvage logging (e.g., economically valuable conifer forests), mixed evergreen hardwood systems are extremely understudied. Here we investigated the impact of high severity wildfire and post-fire salvage logging on the physiological recovery of four resprouting evergreen tree species: Pacific madrone (Arbutus menziesii), tanoak (Notholithocarpus densiflorus), coast live oak (Quercus agrifolia), and California bay (Umbellularia californica). We collected water potential, hydraulic, anatomical and leaf data on resprouts occurring at the intact and salvage logged sites, in addition to microclimate data, over a period of two years. We found few significantly different trait effects as a result of salvage logging, suggesting a robust recovery ability of these tree species to repeated disturbance events.

Monitoring stem radial intra-annual growth dynamics is a useful approach for characterising tree growth responses to climate change. In the Mediterranean there have been only a few studies reporting growth responses of cork oak (Quercus suber L.) to seasonal water shortages. In this study, we focused on direct monitoring of intra-annual radial growth of mature cork oaks over nine complete years, under a 10-year cork harvesting cycle. Band dendrometers were used to assess growth seasonality in two contrasting sites regarding dryness. We hypothesised that summer dormancy and growth bimodality could vary between sites as they are strongly dependent on environmental conditions. Also, we hypothesised that within sites, growth bimodality intensity might vary over the years following cork harvesting disturbance. Our results revealed that growth bimodality was dominant at the drier site, with trees experiencing growth constraints under high temperatures and lower precipitation at short timescales. In contrast, trees at the wetter site exhibited a consistent summer growth, with high plasticity and responsiveness in their growth phenology, revealing the ability to acclimate in longer timescales. The coupling effects of cork harvesting and growth patterns enhanced the trees’ site-dependent growth strategies. At drier site, trees´ complacent radial growth responses maintain constant growth phenological phases, e.g., timings, and achieve higher peaks with higher growth rates, mainly in the spring (yearly growth range between 9.2 mm.yr^− 1 and 4.4 mm.yr^− 1). At the wetter site, tree’s growth drastic responses are due to varying growth timings and highly sensitive growth peaks and rates (yearly growths ranged between 17.5 mm.yr^− 1 and 5.2 mm.yr^− 1).

Land-use change and climate warming favour the expansion of shrubs in alpine environments, with implications for ecosystem functioning and biogeochemical cycles. Thus, we estimated canopy transpiration and canopy conductance of a Pinus mugo and an adjacent Alnus alnobetula stand on a south-facing steep slope in 2,130 m a.s.l. within the treeline ecotone of the Central Austrian Alps throughout one investigation period. For each species, canopy transpiration was estimated by means of sap flow measurements which were scaled up to the stand canopy level. Independent of species, soil water content hardly affected sap flow density, indicating that P. mugo and A. alnobetula are extremely tolerant to limited topsoil water availability. By contrast, sap flow density was strongly correlated with solar radiation and vapour pressure deficit (VPD), while canopy conductance declined with increasing VPD. Our estimated canopy transpiration averaged 2.4 ± 0.1 mm d⁻¹ in P. mugo and 3.0 ± 0.1 mm d⁻¹ in A. alnobetula. The corresponding values for canopy conductance were 37 ± 2 and 42 ± 2 mm s⁻¹, respectively. The observation that, within the treeline ecotone on Mt. Patscherkofel, canopy transpiration of P. mugo and A. alnobetula stands is noticeably higher than that of adjacent low-stature vegetation and isolated trees should be considered when forecasting potential effects of climate and land-use change on the water balance of the treeline ecotone.

Prunus sibirica is a pioneer species for establishing soil-water conservation forests. The study investigated root growth and development in P. sibirica plantation forests to reveal the nutrient flow and material cycling rules during the growth process. Using four diameter classes, total excavation was employed to quantify root biomass and spatial distribution, while anatomical structure and physiological indices were measured to assess adaptation features. Significant differences (P < 0.05) were found in the spatial biomass distribution, anatomical structure, antioxidant enzyme activity, and osmotic adjustment among the different diameter classes of P. sibirica roots. Root biomass increased with diameter class. Significant positive correlations were identified among tree height, basal diameter, and total root biomass. Three-dimensional mapping of coarse root distribution revealed that as diameter class increased, the horizontal distribution range gradually expanded and vertical penetration deepened, exhibiting pronounced spatial asymmetry. Anatomical analysis showed that within the same diameter class, xylem diameter, phloem thickness, periderm thickness, and vascular cambium thickness all increased with root diameter. The large-diameter class of P. sibirica root systems had high levels of antioxidant enzymes and osmoregulatory substances. Root antioxidant enzyme activity, osmoregulatory substance concentration, and membrane stability decreased with increasing soil depth, while root vigor increased. These results suggest the large-diameter class of P. sibirica root systems has a high root absorption capacity and can accumulate more organic matter, making them more resilient to adverse conditions.

Key message

There is a robust linear relationship between the proportionality coefficients of the Montgomery and Montgomery–Koyama–Smith equations.

Abstract

The Montgomery equation (ME) assumes a proportional relationship between individual leaf area and the product of leaf length and width, whereas the Montgomery–Koyama–Smith equation (MKSE) assumes a proportional relationship between the total leaf area per shoot and the product of the sum of individual leaf widths and maximum leaf length. Given the developmental homology between petals and leaves, the ME and MKSE are hypothesized to also apply to petal and corolla areas. However, prior studies have neglected the potential link between their respective proportionality coefficients. To validate the ME and MKSE for calculating individual petal area (A) and total corolla area per flower (A_T), and to test the correlation between the ME and MKSE proportionality coefficients (k for ME and k_KS for MKSE), we measured 2700 petals from 540 flowers across nine Malus cultivars. Goodness of fit was assessed using the root-mean-square error (RMSE) and the coefficient of determination (r²). The ME and MKSE were validated for all nine cultivars, effectively predicting A and A_T with high precision (as gauged by low RMSE and high r²). Importantly, a statistically significant one-to-one (isometric) scaling relationship was observed between k and k_KS. The isometric relationship between the two proportionality coefficients provides a quantitative link between individual petal geometry and whole-corolla structure, significantly simplifying the non-destructive estimation of corolla area (and potentially shoot-level total leaf area).

Accurate estimation of forest aboveground carbon stock (FCS) in moso bamboo (Phyllostachys edulis) forests is of great significance for climate change mitigation, forest management, and achievement of carbon neutrality goals. This can be possible when there exist comprehensive models developed with the important enviromental factors. However, previous studies largely rely on the models dominated by stand structural variables, which are insufficient to fully capture the effects of topography, soil, and climate factors. Moreover, systematic evaluation of performance differences among modeling approaches under progressive multi-factor coupling, as well as their ability to characterize the distributional features of FCS, remain limited, thereby constraining model interpretability and generalizability. Based on the sample plot-level survey data from moso bamboo forests across eight provinces, this study developed five FCS models with different combinations of explanatory variables. After confirming the absence of multicollinearity among predictors, the fitting and predictive performances of traditional ordinary least squares (OLS) regression and machine learning methods, including random forest (RF) and support vector machine (SVM), were systematically evaluated. The results showed that the gradual inclusion of topographic, soil, and climatic factors led to the moderate improvements in the fitting accuracy of OLS models, whereas machine learning models, particularly the RF model, exhibited substantially higher explanatory power, prediction accuracy, and stability under multi-factor coupling conditions (R² > 0.564). These models were more effective in capturing complex nonlinear relationships between FCS and multiple driving factors. Variable importance analysis indicated that stand structural factors, especially basal area and mean stand height, were the dominant determinants of FCS. Topography (elevation), soil (bulk density and soil rock fragment content), and climatic (degree-days above 18 °C and Hargreaves reference evaporation) factors played important regulatory roles through nonlinear relationships. The relative contributions of topographic, soil, and climatic factors ranged from 3.82% to 15.16%, 9.55% to 17.89%, and 3.42% to 23.32% to the models, respectively, with climatic factors exerting a stronger influence than soil factors. This study addresses the limitations of traditional FCS estimation models in representing environmental heterogeneity and nonlinear processes in the complex forest ecosystems and large scale applications. The findings demonstrate that the multi-factor coupling models based on stand structures, integrated with multidimensional environmental information and implemented using machine learning approaches, such as random forest, provide the effective means to enhance the stability and accuracy of regional-scale forest aboveground carbon stock estimation.