Oak radial growth responses to summer climate are primarily structured by water-balance dynamics and shaped by environmental context and species drought tolerance. Global warming is increasingly altering climate constraints on forest growth, particularly for widespread and ecologically important tree taxa such as oak, which dominate many temperate forests and provide critical ecosystem functions. However, the relative importance of different summer climatic drivers and the mechanisms underlying their effects on oak radial growth remain poorly synthesized across the Northern Hemisphere. Employing a multilevel meta-analytic approach, we systematically quantified the associations between summer climatic variables (temperature, precipitation, and the Standardized Precipitation Evapotranspiration Index (SPEI)) and oak radial growth based on 241 effect sizes from 60 publications, while also evaluating the moderating roles of leaf habit, drought tolerance, region, proxy type, seasonal timing (month), and SPEI timescale. Results indicated that summer temperature was negatively associated with oak radial growth, whereas summer precipitation and SPEI showed positive associations. Precipitation sensitivity was strongest in June, while the pooled SPEI effect across reported timescales was the strongest among the three climatic factors and increased with SPEI timescale. SPEI responses also varied geographically and with species-level drought tolerance, highlighting the context dependence of oak sensitivity to summer water availability. Overall, these findings emphasize the importance of water availability for oak radial growth during the summer growing season and provide a quantitative basis for understanding its climate sensitivity under future warming.
Urban greening trees reduce atmospheric fine particulate matter (PM), including black carbon (BC) particles, by rigidly retaining them on their leaves due to the leaf epicuticular wax and leaf surface microstructure. This study investigated the relationship between the interspecific difference in the amount of BC particles retained on the leaves, and leaf chemical and physical characteristics of mature Lithocarpus edulis and Ilex rotunda trees in an urban area of Tokyo, Japan. From May to November 2023, the amount of leaf epicuticular wax and leaf surface roughness of L. edulis were consistently higher than those of I. rotunda. This is because the leaves of L. edulis exhibited a thick-flat epicuticular wax layer on the adaxial surface and a considerably rough abaxial surface with trichomes located within cracks of film-shaped wax. From May to July, the leaf BC amounts of L. edulis were higher than those of I. rotunda. However, the leaf BC amounts of I. rotunda were higher than those of L. edulis in October and November. We developed an assessment index of leaf epicuticular wax hydrophobicity (HwLS) based on the chemical composition (e.g., alkanes) of the wax per unit leaf surface area (LSA). Throughout the experimental period, the HwLS showed a strong positive correlation with the leaf BC amount of both tree species. This study is the first to reveal that both leaf chemical and physical characteristics regulate the ability of mature urban greening trees to retain atmospheric BC particles on the leaves. The hydrophobicity of leaf epicuticular wax and leaf surface area regulate the ability of urban greening trees to retain atmospheric black carbon particles on the leaves.
Emerging technologies facilitated effective crossdating of silver maple tree rings, revealing synchronous growth patterns and highlighting the dendrochronological potential of this species. Silver maple (Acer saccharinum L.) is a fast-growing, flood-tolerant species common in bottomland forests of eastern North America. Tree-ring research on silver maple is limited due to the species’ relatively short lifespan and reputation for indistinct rings. Here, we investigated crossdating and growth patterns of silver maple trees from 12 sites along the Upper Mississippi River floodplain. Crossdating this species was challenging due to the presence of false, micro, and locally absent rings. Despite these challenges, we successfully developed 12 silver maple chronologies by combining traditional dendrochronological methods with high-resolution imaging of specimens and an image-based approach to measuring rings and annotating anatomical features. Silver maple trees exhibited high growth variability, robust site-level crossdating (0.50–0.68 mean interseries correlations), and a common regional growth signal, including wide marker rings that were synchronous among sites and coincided with major flood events in the Upper Mississippi River (1965, 1986, 1993, 2001, 2011). The chronologies developed here may have a variety of ecological and management applications, including accurate determination of tree age and analyses of growth response to flooding. Our study demonstrates the considerable dendrochronological potential of silver maple from this region.
In Camellia sinensis 'Aijiao Oolong', from the bud stage to the full-bloom stage, amino acids (especially theanine) significantly increased, whereas catechins and alkaloids decreased. Transcriptomic analysis revealed extensive developmental-stage-associated changes in 8 hormone-related signaling pathways, among which auxin signaling contained the largest number of DEGs. As reproductive, non-leaf organs of tea plants, tea flowers are rich in bioactive substances and possess great potential for high-value utilization. However, the mechanisms underlying flower development in the distinctive oolong tea cultivar Aijiao Oolong remain unclear. This study integrated targeted metabolomics and transcriptomics to analyze tea flowers at the bud and full-bloom stages. The sum of the 25 quantified free amino acids was 35.26 mg/g at the full-bloom stage, 1.66-fold that at the bud stage (21.28 mg/g). 18 quantified free amino acids showed significantly higher contents at the full-bloom stage, whereas aspartic acid showed a significantly lower content and six amino acids showed no significant difference. Theanine was the most abundant quantified free amino acid and increased from 8.84 to 13.98 mg/g. In contrast, the sums of the nine quantified catechins and three quantified purine alkaloids were lower at the full-bloom stage. Transcriptomic analysis identified 122 DEGs associated with 8 hormone-related signaling pathways. Among them, auxin signaling contained the largest number of DEGs and exhibited extensive transcriptional changes, suggesting that auxin-related signaling may be prominently involved in flower development. Integrated pathway analysis indicated that changes in nitrogen and amino-acid metabolism were associated with higher amino-acid contents, whereas changes in flavonoid and purine metabolism were associated with lower catechin and caffeine contents. These findings provide an integrated view of developmental-stage-associated metabolic and transcriptional changes in Aijiao Oolong tea flowers, providing insights into flower development and the potential high-value utilization of tea flowers.
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
