The distribution of vessels in broadleaf timber, is directly related to water transport efficiency and safety. Here, I tested the hypothesis that vessel characteristics depend on cambial age (CA) and flow path-length (PL) within the tree rather than solely on CA by measuring vessel hydraulic diameter (VD), vessel frequency (VF), theoretical specific hydraulic conductivity (k _s), and theoretical implosion resistance (VIR) in every growth ring of birch (Betula platyphylla Roth.) tree root, trunk, and branch samples. The effects of CA and PL were analyzed using a linear mixed model. Differences in the vessel characteristics are significant between CA, between PL, and between the interaction of CA and PL. VD decreased linearly and VF increased nonlinearly with PL. The PL explained 59.3 and 67.3 % of the longitudinal variation in VD and VF, respectively. k _s decreased nonlinearly and VIR increased linearly with PL. The PL explained 25.6 and 43.3 % of the longitudinal variation in k _s and VIR, respectively. Radial changes were evident above ground, VD increased, and VF decreased with CA for the first 10–20 years and remained constant thereafter. k _s exhibited a logarithmic increase and VIR exhibited logarithmic decrease with CA. Variable radial patterns were observed below ground. The CA explained 30.9–98.8 %, 23.7–96.9 %, 42.9–96.8 %, and 50.9–98.5 % of the radial variation in VD, VF, k _s, and VIR, respectively. The results suggest that vessel characteristic changes are determined by CA and PL. While growing, trees adjust their vessels to maximize water transport efficiency and ensure mechanical safety.

Real-time quantitative PCR (RT-qPCR) has a high sensitivity and strong specificity, and is widely used in the analysis of gene expression. Selecting appropriate internal reference genes is the key to accurately analyzing the expression changes of target genes by RT-qPCR. To find out the most suitable internal reference genes for studying the gene expression in Broussonetia papyrifera under abiotic stresses (including drought, salt, and ZnSO₄ treatments), seven different tissues of B. papyrifera, as well as the roots, stems, and leaves of B. papyrifera under the abiotic stresses were used as test materials, and 15 candidate internal reference genes were screened based on the transcriptome data via RT-qPCR. Then, the expression stability of the candidate genes was comprehensively evaluated through the software geNorm (v3.5), NormFinder (v0.953), BestKeeper (v1.0), and RefFinder. The best internal reference genes and their combinations were screened out according to the analysis results. rRNA and Actin were the best reference genes under drought stress. Under salt stress, DOUB, HSP, NADH, and rRNA were the most stable reference genes. Under heavy metal stress, HSP and NADH were the most suitable reference genes. EIF3 and Actin were the most suitable internal reference genes in the different tissues of B. papyrifera. In addition, HSP, rRNA, NADH, and UBC were the most suitable internal reference genes for the abiotic stresses and the different tissues of B. papyrifera. The expression patterns of DREB and POD were analyzed by using the selected stable and unstable reference genes. This further verified the reliability of the screened internal reference genes. This study lays the foundation for the functional analysis and regulatory mechanism research of genes in B. papyrifera.

Euonymus microcarpus (Oliv.) Sprague, is a species of evergreen shrub of the genus Euonymus, family Celastraceae. Here, we extracted the genomic DNA from the leaves of E. microcarpus and constructed a paired-end library. The chloroplast genome of E. microcarpus was generated with the high-throughput sequencing by the illumina Hiseq X Ten platform and de novo assembly. The chloroplast genome had a quadripartite structure, containing a long single copy region with a size of 85,386 bp and a short single copy region with a size of 18,456 bp, separated by two inverted repeat regions of 26,850 bp. The chloroplast genome contained 133 genes identified in total, including 87 potential protein-coding genes, 38 transfer RNA genes, and eight ribosomal RNA genes. A total of 282 simple sequence repeats and 63 long repeats were found. Furthermore, the phylogenetic relationships inferred that E. microcarpus is sister to E. japonicus and E. schensianus. A comparison of the structure of the chloroplast genomes of eight Euonymus species suggests a nucleotide variability of the junction sites and a higher divergence of non-coding regions, compared to the coding regions. The original findings of the study serves as a good reference for chloroplast genome assembly and a valuable foundation for the genetic diversity and evolution of E. microcarpus.

Wood can store carbon and help mitigate global climate change. Carbon density (CD), the basis for measuring and analyzing C storage, is the product of wood density (WD) and C concentration, which are dependent on wood structure, cellulose concentration (CC), hemicellulose concentration (HC), and lignin concentration (LC). However, little attention has been paid to the C concentration of cellulose, hemicellulose, and lignin, which are fundamental factors in C storage and affect the credibility of accurate CD estimates. In order to disentangle the CD drives, WD, C concentration, CC, HC, and LC of the branch, stem, and root were quantified for five Rosaceae species from temperate forests in Northeastern China. The species were Sorbus alnifolia (Sieb.et Zucc.) K. Koch, Pyrus ussuriensis Maxim., Malus baccata (L.) Borkh., Crataegus pinnatifida var. major N. E. Brown, and Padus racemosa (Linn.) Gilib. The WD, CC, HC, and LC differed among species and tree organs, with the highest variability for the HC. The structural carbon concentration (SCC) was lower than the organic carbon concentration (OCC) and even the Intergovernmental Panel on Climate Change (IPCC) default value of 45%, with a maximum deviation of 2.6%. CD differed dramatically among species and tree organs. Based on SCC calculations, the highest CD was found in Sorbus alnifolia root (0.27 × 10⁶ g/m³), while the lowest was found in Padus racemosa branch (0.22 × 10⁶ g/m³). The results suggest that when estimating CD accurately at species level, it is important to consider not only WD but also structural carbohydrates and lignin concentration, providing important information on C fluxes and long-term C sequestration for forests. The study findings provide valuable insights into CD variations among tree species and organs and are valuable for forest management and policy development to improve carbon sequestration.