Changes in the physiological activity of parenchyma cells in Dalbergia odorifera xylem and its relationship with heartwood formation.

BACKGROUND: The formation of a tree's heartwood gives the wood properties such as natural decay resistance and aesthetic color, and often directly determines the value of wood products. Regulating the quantity and quality of heartwood is of great importance to the use of wood. However, the mechanism of heartwood formation has been poorly understood. RESULTS: Using Dalbergia odorifera as the study species, the number of starch grains, the morphology of the nuclei, the changes in the content of water and secondary metabolites were observed continuously in the radial direction of the xylem. The results show that from the outer toward inner sapwood, the starch grains are abundant, the length to diameter ratio of the nuclei is decreasing, and the morphology changes from elongated elliptical and then to round. In the outer transition zone, the starch grains begin to decrease abruptly and the nuclei shrink at a slower rate, with a radial width of approximately 2 mm. In the inner transition zone, the heartwood color begins to appear, the starch grains disappear and a few nuclei with reduced fluorescence are present, with a radial width of approximately 1 mm. Heartwood formation after complete disappearance of the nuclei. The moisture content of the heartwood is higher than that of the sapwood, and the inner transition zone is where the content rises. The secondary metabolites of the heartwood begin to accumulate in large quantities in the inner transition zone. CONCLUSION: Based on the physiological changes of parenchyma cells in the xylem, the radial width of the transition zone of Dalbergia odorifera is clearly defined as approximately 3 mm. Both the water and secondary metabolite abrupt changes occur at the final stage of programmed cell death, and neither is a direct cause of programmed cell death in parenchyma cells.

The DNA barcode identification of Dalbergia odorifera T. Chen and Dalbergia tonkinensis Prain.

BACKGROUND: Dalbergia odorifera is a precious tree species with unique economic and medicinal values, which is difficult to distinguish from Dalbergia tonkinensis by traditional identification methods such as morphological characteristics and wood structure characteristics. It has been demonstrated that the identification of tree species can be effectively achieved using DNA barcoding, but there is a lack of study of the combined sequences used as DNA barcodes in the two tree species. In this study, 10 single sequences and 4 combined sequences were selected for analysis, and the identification effect of each sequence was evaluated by the distance-based method, BLAST-based search, character-based method, and tree-based method. RESULTS: Among the single sequences and the combined sequences, the interspecies distance of trnH-psbA and ITS2 + trnH-psbA was greater than the intraspecies distance, and there was no overlap in their frequency distribution plots. The results of the Wilcoxon signed-rank test for the interspecies distance of each sequence showed that the interspecies differences of the single sequences except trnL-trnF, trnH-psbA, and ycf3 were significantly smaller than those of the combined sequences. The results of BLAST analysis showed that trnH-psbA could accurately identify D. odorifera and D. tonkinensis at the species level. In the character-based method, single sequences of trnL-trnF, trnH-psbA with all the combined sequences can be used for the identification of D. odorifera and D. tonkinensis. In addition, the neighbor-joining (NJ) trees constructed based on trnH-psbA and ITS2 + trnH-psbA were able to cluster D. odorifera and D. tonkinensis on two clades. CONCLUSIONS: The results showed that the character-based method with the BLOG algorithm was the most effective among all the evaluation methods, and the combined sequences can improve the ability to identify tree species compared with single sequences. Finally, the trnH-psbA and ITS2 + trnH-psbA were proposed as DNA barcodes to identify D. odorifera and D. tonkinensis.

Function of the R2R3-MYB Transcription Factors in Dalbergia odorifera and Their Relationship with Heartwood Formation.

R2R3-MYB transcription factors (TFs) form one of the most important TF families involved in regulating various physiological functions in plants. The heartwood of Dalbergia odorifera is a kind of high-grade mahogany and valuable herbal medicine with wide application. However, the role of R2R3-MYB genes in the growth and development of D. odorifera, especially their relevance to heartwood formation, has not been revealed. A total of 126 R2R3-MYBs were screened from the D. odorifera genome and named DodMYB1-126 based on their location on 10 chromosomes. The collinearity results showed that purification selection was the main driving force for the evolution of the R2R3-MYB TFs family, and whole genome/fragment replication event was the main form for expanding the R2R3-MYB family, generating a divergence of gene structure and function. Comparative phylogenetic analysis classified the R2R3-MYB TFs into 33 subfamilies. S3-7,10,12-13,21 and N4-7 were extensively involved in the metabolic process; S9,13,16-19,24-25 and N1-3,8 were associated with the growth and development of D. odorifera. Based on the differential transcriptional expression levels of R2R3-MYBs in different tissues, DodMYB32, DodMYB55, and DodMYB89 were tentatively screened for involvement in the regulatory process of heartwood. Further studies have shown that the DodMYB89, localized in the nucleus, has transcriptional activation activity and is involved in regulating the biosynthesis of the secondary metabolites of heartwood by activating the promoters of the structural genes DodI2'H and DodCOMT. This study aimed to comprehensively analyze the functions of the R2R3-MYB TFs and screen for candidate genes that might be involved in heartwood formation of D. odorifera.

Differences in Chemical Constituents between Dalbergia oliveri Heartwood and Sapwood and Their Effect on Wood Color.

The purpose of this study was to characterize and quantify the chemical constituents of heartwood and sapwood of Dalbergia oliveri extract in order to investigate the chemical components that determine the formation of heartwood's color. In this work, the types of pigments in heartwood and sapwood extract were analyzed using UV-Visible (UV) Spectrophotometer, and the main pigment components of heartwood and sapwood extract were identified and quantified using ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS). The results showed that the difference in content of the main components between heartwood and sapwood of Dalbergia oliveri was slight, and the lignin structure between heartwood and sapwood is basically identical; flavonoid pigments were found to be the primary chromophoric components of heartwood and sapwood extract. However, a total of 21 flavonoids were identified in heartwood and sapwood, of which the unique substances to heartwood were vitexin, isorhamnetin, and pelargonidin, and the content of isoliquiritigenin, formononetin, and biochanin A were 253, 37, and 583 times higher in the heartwood than in the sapwood, respectively, which could be the main pigment components affecting the significant color difference between heartwood and sapwood of Dalbergia oliveri. These results will provide a foundation for revealing the underlying mechanism of color difference between heartwood and sapwood and provide a theoretical basis for wood coloring.

Adsorption Property, Kinetic and Equilibrium Studies of Activated Carbon Fiber Prepared from Liquefied Wood by Zncl2 Activation.

Activated carbon fiber was prepared from liquefied wood by chemical activation with ZnCl2 (Z-LWACF) at different impregnation ratios, with a particular focus on its adsorption property, kinetic and isotherm. The characterization and properties of Z-LWACFs were investigated by nitrogen adsorption/desorption, X-ray photoelectron spectroscopy (XPS), methylene blue (MB) and iodine adsorption. Two activation process methods were employed to prepare Z-LWACF and contrasted with others fibers. The results showed that the Z-LWACF obtained by one-step ZnCl2 activation present higher yields and specific surface area than others fibers. Besides, the change of MB adsorption value at different impregnation ratios was consistent with pore structure distribution above 1.5 nm pore size, indicating that larger micropores (1.5 to 2 nm) and mesopores played a major role in the MB adsorption by Z-LWACF. The kinetics of MB adsorption process was found to follow the pseudo-second-order kinetic model and the adsorption rate was controlled by chemisorption. It was also found that MB adsroption by Z-LWACF belonged to monolayer adsorption and Z-LWACF was easy to adsorb MB.