Heartwood Formation Research Articles

Effect of Perforation Dyeing Technique on Color Difference, Colorfastness, and Basic Density of Living Red-Heart Chinese Fir

Red-heart Chinese fir is an excellent geographic provenance of Cunninghamia lanceolata, with high-value red heartwood. However, the formation of red heartwood is usually slow. To quickly cultivate red-heart Chinese fir, we studied perforation dyeing technology on living trees that were 7 years old and efficient in high-value red heartwood formation. Reactive dye (%), penetrant (%), KH2PO4 (%), and pH were selected as influencing factors, and an orthogonal test (L9(3)4) was used. The results showed that the total color difference between the experimental and CK groups ranged from 13.74 to 26.86 NBS, which was a significant visual perception (above 12 NBS). The total color difference before and after soaking in water for 6 h ranged from 2.30 to 5.12 NBS, which belonged to the detectable and identifiable value of the human eye (2~5 NBS). After the injection of the dye liquid, the wood basic density (WBD) was significantly affected after one year. After a comprehensive analysis of wood color difference, colorfastness, and WBD of the orthogonal test, the best dyeing process of juvenile red-heart Chinese fir was reactive dye: 0.8%, penetrant: 0.05%, KH2PO4: 0.3%, and pH: 3.5. The results of this study can provide a reference to improve the value of red-heart Chinese fir, a fast-cultivated, high-value decorative wood material.

Drought could promote the heartwood formation in Dalbergia odorifera by enhancing the transformation of starch to soluble sugars

ABSTRACT The heartwood of Dalbergia odorifera T. Chen (D. odorifera) is highly valuable. It was speculated that drought could promote heartwood formation in D. odorifera. To test this hypothesis, we artificially simulated conditions of low and high soil moisture content and investigated whether D. odorifera trees living in habitats with contrasting soil water conditions display distinct heartwood formation. Besides, we performed a preliminary study to explore the possible mechanism of drought affecting heartwood formation in D. odorifera in terms of non-structural carbohydrates (NSC). Higher heartwood formation percentage and heartwood size were observed in drought-treated trees. The heartwood density of drought-treated trees was significantly greater than that of control and the oil content of heavy drought-treated heartwood was significantly higher than that of the other treatments. None of water treatments had a significant effect on the essential oil components of heartwood. Furthermore, the effects of water treatments on the total amount of NSC were very limited; however drought treatments enhanced the transformation of starch to soluble sugars compared to control. This study confirmed the hypothesis that drought could promote the heartwood formation in D. odorifera, not by changing the total amount of NSC but by changing the component proportion of NSC.

Assessment of Variations in Growth, Bark thickness and Heartwood Content of Different Populations of Redsanders (<i>Pterocarpus santalinus</i>) in Karnataka

Red sanders is one of the highly valued tree species in the world, native to south parts of Eastern Ghats (Andhra Pradesh and Tamil Nadu). As the success of any tree improvement depends upon the amount of variations found in heritable traits of populations and is basis for future genetic improvement, the present study was carried out to assess the variations in growth traits, bark, sap- and heartwood of different populations of red sanders in Karnataka. Hullikere (43 years), K.Settihalli (47 years), Jharakabande (32 years), Nallal (42 years), Yeshwanpur -A (42 years) and Yeshwanpur-B (42 years) in Karnataka. Significant variability found in growth traits viz., girth, straightness, tree height and sap- and heartwood content of the Red sanders. Time of heartwood formation varies within and between trees as well as between the populations. Both content and colour of heartwood vary even in the trees of same girth in a stand. No heartwood was found in trees which had girth <37, <41, <44, <46 and <48cm at breast height in Jharakabande, Hullikere and Yeshwanpur-B, Yeshwanpur A, Nallal and K.Settihalli plantations, respectively. The heartwood formation was not depicted any trend with tree size and age of trees in the Redsanders populations.

The changes of extractive contents of youngSwietenia mahagoni(L.) Jacq trees during heartwood formation

AbstractWe investigated the distribution of extractive, phenolic, and polysaccharides content of youngS. mahagonitrees aged 1 to 5 years. The wood powder materials in two vertical positions (bottom and top) were successively extracted using n-hexane, methanol, and hot water solutions. The results showed that there was a significant interaction between the tree age and axial position in all parameters. The methanol and total extractive content decreased significantly from 1 to 3-year-old at the top part. In contrast, the amount of hot water and total extractive increased significantly from 3 to 4-year-old trees at the bottom part. Furthermore, a significant increase was also found at the bottom heartwood for hexane, methanol, and the total extractive from 4 to 5-year-old trees. The reverse trend was observed in the polar fractions (methanol and hot water) at the top of the trees. Generally, the extractive pattern tends to decrease from bottom to top with the highest proportion of methanol extract (70% based on the total extractive weight), and it increased from sapwood to heartwood. The total phenolic content (TPC) and total soluble polysaccharides (TSP) generally increase with tree age (except for TSP from 2 to 3-year-old trees at the top part). The high content of TPC in the heartwood and TSP in the sapwood indicated the process of heartwood formation. In addition, a drastic decrease in the methanol extract and TSP at the age of 3 years at the top indicated that the TSP was transferred from top to bottom for the heartwood formation at the bottom part of 4-year-old trees.

Morphological and molecular features of stain fungi infecting rubberwood (Hevea brasiliensis)

Abstract. Nandika D, Arinana, Salman ABA, Putri JY. 2021. Morphological and molecular features of stain fungi infecting rubberwood (Hevea brasiliensis). Biodiversitas 22: 5408-5416. In the southeast Asia region, particularly Indonesia, Thailand, and Malaysia, rubberwood (Hevea brasiliensis Muell. Arg.) has been widely used as a raw material in various industries particularly furniture manufacturing. However, rubberwood is highly susceptible to fungal attack due to its lack of heartwood formation. A laboratory study was conducted to investigate the morphological and molecular features of stain fungi infecting rubberwood. A total of five isolates of stain fungi belonging to three genera were identified based on internal transcribed spacer (ITS) and morphological features. All isolates belong to Order Eurotiales with each genus being Paecilomyces, Aspergillus, and Penicillium. The highest growth rate on wood samples was shown by Aspergillus chevalieri section Aspergillus and Paecilomyces maximus or P. formosus with values of 86.57% and 86.22%, respectively. All of the stain fungi genera caused varied level of discoloration on wood samples with dark grayish and very dark grayish as the more frequent color found. Quantitatively, the highest discoloration was shown by A. chevalieri section Aspergillus (?E = 27.60) and P. maximus or P. formosus (?E = 16.69). These species can be considered as newly stain fungi recorded infecting rubberwood in Indonesia. In addition, discoloration caused by these two stain fungi was the worst.

Heartwood and Sapwood Variation and Development in Chenshan Red-Heart Chinese Fir (Cunninghamia lanceolata (Lamb.) Hook)

Abstract Chenshan red-heart Chinese fir is a provenance of Cunninghamia lanceolata, with high-value red heartwood, which is widely used in high-quality furniture and construction. Yet, there is still little information on heartwood development of this tree for high-value decorative timber, which is essential to improve one's plantation management strategy. Here, we investigated the horizontal and vertical variation of heartwood and sapwood and simulated heartwood formation process using stem analysis method. We selected 15 sample trees from five plots of 20 m × 30 m in Chenshan red-heart Chinese fir plantations (9, 15, 26, 29, and 34 years old, respectively). The results showed that Chenshan red-heart Chinese fir stems began to form heartwood when the xylem diameter reached 4 to 8 cm. The heartwood diameter and area, as well as the sapwood area, all increased in the different-aged Chenshan red-heart Chinese firs with increasing xylem diameter and decreased with increasing tree height. As tree height increased, the red heartwood formation rate declined at all ages. Relationship analysis showed that xylem diameter was the most important factor influencing heartwood formation. Red heartwood rate at breast height could be modeled by logistic models. We concluded that heartwood formation began at about 7 years old, and the formation rate increased until peaking at 60 percent at 40 years old. In conclusion, it will be imperative to prolong the Chenshan red-heart Chinese fir rotation period from the currently common 25 years to about 40 years to achieve the maximum sustainable yield of high-value decorative timber.

Variations in heartwood formation and wood density as a function of age and plant spacing in a fast-growing eucalyptus plantation

Abstract The heartwood formation process is little known in fast growing plantation woods. Therefore, the aims of this study were to determine how planting spacing and tree age affect the formation and proportion of heartwood and sapwood, as well as the density of eucalyptus wood. Trees from a eucalyptus clonal plantation (Eucalyptus grandis × E. urophylla hybrid) cultivated in three spacings (3 × 1, 3 × 2 and 3 × 3 m) were sampled at 14, 27, 32, 53, 64 and 76 months of age. Heartwood percentage was quantified with Dimethyl yellow indicator, while the wood density was determined by X-ray densitometry. The heartwood percentage, wood volume, heartwood density and wood density were correlated with the different growth rates. The heartwood formation process started between 32 and 53 months, regardless of spacing. The heartwood proportion doubled with increasing age in the widest spacing and increased about four times in 3 × 1 and 3 × 2 m spacing. The planting spacing influenced the growth rates of the trees, but did not affect the heartwood and sapwood percentage or density. The greatest increase in density values occurred between the first year of growth (14 months) and the beginning of heartwood formation (53 months).

Lignification and cell wall thickening of ray parenchyma cells in Scots pine sapwood

Abstract Scots pine exhibits variations in ray anatomy, which are poorly understood. Some ray parenchyma cells develop thick and lignified cell walls before heartwood formation. We hypothesized that some stands and trees show high numbers of lignified and thick-walled parenchyma cells early in the sapwood. Therefore, a microscopic analysis of Scots pine sapwood from four different stands in Northern Europe was performed on Safranin — Astra blue-stained tangential micro sections from outer and inner sapwood areas. Significant differences in lignification and cell wall thickening of ray parenchyma cells were observed in the outer sapwood between all of the stands for the trees analyzed. On a single tree level, the relative lignification and cell wall thickening of ray parenchyma cells ranged from 4.3% to 74.3% in the outer sapwood. In the inner sapwood, lignification and cell wall thickening of ray parenchyma cells were more frequent. In some trees, however, the difference in lignification and cell wall thickening between inner and outer sapwood was small since early lignification, and cell wall thickening was already more common in the outer sapwood. Ray composition and number of rays per area were not significantly different within the studied material. However, only one Scottish tree had a significantly higher number of ray parenchyma cells per ray. The differences discovered in lignification and cell wall thickening in ray parenchyma cells early in the sapwood of Scots pine are relevant for wood utilization in general and impregnation treatments with protection agents in particular.

Variation of Chemical Components in Sapwood, Transition Zone, and Heartwood of Dalbergia odorifera and Its Relationship with Heartwood Formation

Heartwood has a high economic value because of its natural durability, beautiful color, special aroma, and richness in active ingredients used in traditional Chinese medicine. However, the mechanism of heartwood formation remains unclear. Dalbergia odorifera was selected as the object of research to analyze this variation in the chemical composition of sapwood, transition zone, and heartwood as well as to elucidate the relationship between this variation and the formation of heartwood. The variation of secondary metabolites was analyzed using gas chromatography-mass spectrometry and ultra-high performance liquid chromatography–mass spectrometry, the variation of lignin was analyzed using Fourier transform infrared spectroscopy and ultraviolet visible spectrophotometry, and the variation law of mineral elements was analyzed using atomic absorption spectrophotometry. The results demonstrated that contents of characteristic secondary metabolites in Dalbergia odorifera were mainly distributed in heartwood (84.3–96.8%), increased from the outer to inner layers of the xylem, and sudden changes occurred in the transition zone (the fourth growth ring). The Dalbergia odorifera lignin can be identified as typical “syringyl–guaiacyl (S–G)” lignin, and the color darkened from the outside to the inside. The results demonstrated that there were more benzene rings and conjugated C=O structures in the heartwood. Additionally, the variation of minerals in the xylem was related to elemental types; the average concentrations of Mg, Ca, Fe and Sr were higher in the heartwood than in the sapwood, whereas the concentrations of K and Zn were higher in the sapwood than in the heartwood owing to the reabsorption of elements. The concentrations of Na and Cu were similar in the heartwood and sapwood. The composition and structural characteristics of secondary metabolites, lignin, and mineral elements in the three typical xylem regions (sapwood, transition zone and heartwood) of Dalbergia odorifera changed. The most abrupt change occurred in the narrow xylem transition zone, which is the key location involved in heartwood formation in Dalbergia odorifera.

Extractives elucidation of Taiwania cryptomerioides sapwood

Taiwania (Taiwania cryptomerioides Hayata) has long been regarded as a living fossil from the Tertiary period of Mesozoic Era for its distinguished yellowish-red color with purplish-pink streaks presented in its heartwood. With this elegant appearance that matches the color “red” for good fortune in the Taiwanese culture, Taiwania is supposed to be a popular wood in Taiwan where it is a native species of. Extractives contribute to the properties of wood. It is a fascinating subject to investigate extractives biosynthesis in the process of heartwood formation. Up to date, there is no phytochemistry study of Taiwania sapwood. In this study, three new sesquiterpenoids, Taiwania A (1), Taiwania B (2), and Taiwania C (3), together with 75 known compounds in the Taiwania sapwood. The structures of extractives were determined by analysis of spectroscopic data and comparison with the literatures. This study supported secondary reaction lignans could be found in sapwood that confirmed our previous research on the Taiwania-type of heartwood formation.

Physiological changes during heartwood formation induced by plant growth regulators in Dalbergia odorifera (Leguminosae)

Abstract There is a need to better understand and promote formation of ‘Jiang Xiang’, the highly valuable heartwood of Dalbergia odorifera T. Chen. Plant growth regulators are the most widely used and generally most effective promoters of heartwood formation. However, to date no method has been proved effective for D. odorifera as little is known about biochemical and physiological change during heartwood development. Four potential heartwood induction substances viz. ethephon, methyl jasmonate, salicylic acid and abscisic acid solutions were injected into the trunk of D. odorifera to determine the effect on heartwood formation and related physiological responses. Non-structural carbohydrates, wood properties, essential oil and histochemical and structural observation were assessed in the post-treatment period. As also observed in the formation of natural heartwood, growth regulator-induced Jiang Xiang production was accompanied by sapwood dehydration, non-structural carbohydrates consumption and synthesis of heartwood specific substances. These substances were synthesized in the ray and axial parenchyma and than transported into the vessels through the pits. As the heartwood substances accumulated, basic density and essential oil content increased gradually, thereby Jiang Xiang was finally produced. In this process, physiological parameters of discoloured sapwood gradually evolved to resemble those of natural heartwood. Ethephon-induced Jiang Xiang was closest to natural heartwood and its density, essential oil content, composition and relative amounts met the standards for high-quality Jiang Xiang, while the other inducers had unsatisfactory induction effects. This study supports the hypothesis that ethephon could be applied to induce formation of Jiang Xiang in D. odorifera.

A transcriptomic view to wounding response in young Scots pine stems

We studied the stress response of five-year-old Scots pine xylem to mechanical wounding using RNA sequencing. In general, we observed a bimodal response in pine xylem after wounding. Transcripts associated with water deficit stress, defence, and cell wall modification were induced at the earliest time point of three hours; at the same time, growth-related processes were down-regulated. A second temporal wave was triggered either at the middle and/or at the late time points (one and four days). Secondary metabolism, such as stilbene and lignan biosynthesis started one day after wounding. Scots pine synthesises the stilbenes pinosylvin and its monomethyl ether both as constitutive and induced defence compounds. Stilbene biosynthesis is induced by wounding, pathogens and UV stress, but is also developmentally regulated when heartwood is formed. Comparison of wounding responses to heartwood formation shows that many induced processes (in addition to stilbene biosynthesis) are similar and relate to defence or desiccation stress, but often specific transcripts are up-regulated in the developmental and wounding induced contexts. Pine resin biosynthesis was not induced in response to wounding, at least not during the first four days.

Elicitors Modulate Young Sandalwood (Santalum album L.) Growth, Heartwood Formation, and Concrete Oil Synthesis.

Five chemical elicitors––6-benzyladenine (BA), ethephon (ETH), methyl jasmonate (MeJA), hydrogen peroxide (H2O2) and calcium chloride (CaCl2)––were used to treat 1- and 5-year-old sandal trees (Santalum album L.) to assess their effects on growth, heartwood formation and concrete oil synthesis. The results showed that some newly formed branches in stems that were induced by BA and ETH displayed leaf senescence and developed new smaller and light-green leaves. The relative percentage of concrete oil from the heartwood of water-treated trees (0.65%) was significantly lower than that from trees treated with 4 mM H2O2 (2.85%) and 4 mM BA (2.75%) within one year. Four mM BA, H2O2 and CaCl2 induced a significantly higher level of sesquiterpenoids than heartwood treated with 2 mM of these elicitors. Four mM MeJA induced significantly less sesquiterpenoids than heartwood treated with 2 mM MeJA. Morphological, physiological, and chromatographic–spectrometric technologies were integrated to trace the potential function of these exogenously applied chemical elicitors. The results may have important applications and provide a better understanding of the molecular mechanism of heartwood formation and hardening in young sandalwood trees.

PHYSIOLOGICAL, BIOCHEMICAL AND MOLECULAR GENETIC ASPECTS OF HEARTWOOD FORMATION MECHANISMS

Heartwood is a physiologically inactive part of the xylem, which is formed as a result of parenchymal cell death and is characterized by the accumulation of extractives that prevent wood from biodegradation. The review summarizes the latest information about the anatomical and biochemical features of heartwood genesis, describes its major stages in the main stand-forming species, and examines the biological role of heartwood. Special attention is given to recent advancements in the study of the genes encoding key enzymes of carbohydrate and phenolic metabolism, hormone metabolism, and some transcription factors that are overexpressed during heartwood formation. The review presents original hypotheses that consider heartwood formation as a form of tissue aging and compare it to programmed cell death.

Allometry rather than abiotic drivers explains biomass allocation among leaves, stems and roots of Artemisia across a large environmental gradient in China

Abstract Biomass allocation patterns reflect the adaptive strategies of plants growing in different environments, which is a central issue in comparative plant ecology and evolution. However, the factors underpinning specific allocation patterns across organs and the existence of general rules governing allocation remain contentious. Optimal partitioning theory (OPT) states that plants can respond to resource availability by allocating relatively more biomass to the organ that captures the most limiting resources to optimize growth. In contrast, allometric partitioning theory (APT) postulates that biomass allocation among organs is a power function of plant size independently of environmental variation. As phylogenetic and growth form constraints (e.g. formation of inert heartwood in tree clades) may also affect biomass allocation, comparison among and within closely related taxa of rather similar growth form may enable a more direct testing of which of these two theories prevails. To test whether OPT or APT was prevalent at wide geographical scale, we investigated biomass allocation patterns among leaves, stems and roots of 1,022 plants of 62 Artemisia species (Asteraceae) collected along broad climate (annual mean temperature range: −4.9 to 18.0°C, annual mean precipitation range: 193–1,668 mm) and soil gradients (soil carbon content range: 1.6–15.4 kg C m−2) in central and eastern China. There were strong allometric relationships among leaf mass (ML), stem mass (MS) and root mass (MR) at both interspecific and intraspecific levels. Moreover, the interspecific and intraspecific patterns were not different from general patterns for pooled plants, that is, ML/MR and ML/MS, but not MS/MR, generally decreased with plant size. However, the three organ mass ratios were not responsive to broad climatic or soil gradients after the effect of plant size was removed. Synthesis. Our results generally support APT instead of OPT, suggesting that Artemisia plants have evolved an allometric strategy rather than relying on adjustment of allocation among organs to adapt to the broadly varying environments at the regional scale. For follow‐up research, we hypothesize that the strong allometric constraints on biomass allocation should depend on strong physiological adaptive responses of the different organs of Artemisia to environmental gradients.

Domestication provides the key to conservation of Santalum yasi – a threatened Pacific sandalwood

ABSTRACT Santalum yasi is a high-value hemiparasitic tree endemic to Fiji, Niue and Tonga. It has been overexploited for its oil-yielding heartwood and is now threatened. Remaining stands lack genetic diversity and are likely to be suffering from inbreeding depression, although the species still has significant genetic diversity overall. We argue that the best way to conserve this species is through an active domestication program that will adequately sample and conserve the genetic base in ex situ and circa situm plantings. The approach to S. yasi tree-breeding can be characterised as a low-input strategy involving the early use of molecular markers for population parameter determination. Long-term success will have strong interdependent links with the conservation of the remaining genetic resources. A strategy based on recurrent selection and breeding for key traits—including heartwood volume and oil yield per year, oil quality and environmental adaptability related to cyclone resistance and the tolerance of pests and diseases—is recommended. The establishment of genetic conservation stands based on collections of the species throughout its natural range in Fiji and Tonga has commenced. Challenges associated with the conservation and domestication of S. yasi are discussed. These include the advanced age required before oil characterisation can be undertaken; the need to assess genotype–host-plant interactions; and the need for comparatively sophisticated equipment and destructive harvesting to carry out oil assessments. Capacity development of professional staff in the Pacific Islands is an additional prerequisite for implementing an effective strategy. Research into the variation and heritability of heartwood formation and oil characteristics, and a better understanding of the breeding biology of S. yasi and geneflow between it and exotic Indian sandalwood (S. album), are high priorities. It will be more than a decade—probably around 20 years—before S. yasi individuals in planned, well-designed trial plantings have sufficient heartwood development to enable oil-trait assessment. Establishment of such trials is an immediate priority. In addition to this long-term activity, we recommend a simple interim strategy that promotes high genetic diversity of seedling-based planting stock. This can be implemented using a combination of gene conservation stands, progeny trials that can be culled to seedling seed orchards, and genetically diverse community-based seed stands. The strategy will both provide a safeguard against the further loss of diversity and promote wide outcrossing. Releasing fragmented populations from inbreeding depression is expected to increase general vigour.

Changes in Non-Structural Carbohydrates, Wood Properties and Essential Oil During Chemically-Induced Heartwood Formation in Dalbergia odorifera.

The highly valuable heartwood of Dalbergia odorifera T. Chen, known as Jiang Xiang in traditional Chinese medicine, is formed very slowly, and there is a need to better understand the process and promote heartwood formation. Chemical induction is considered to be one of the promising methods to induce heartwood formation. However, to date no method has been proved effective for D. odorifera as little is known about biochemical and physiological changes during heartwood development. Three potential heartwood induction substances viz. acetic acid, sodium chloride, and hydrogen peroxide solutions were injected into the trunk of D. odorifera to determine the effect on heartwood formation and physiological activity. Non-structural carbohydrates, lipids, wood properties, and essential oil were assessed in the post-treatment period. As also observed in the formation of natural heartwood, chemical-induced Jiang Xiang production was accompanied by sapwood dehydration, non-structural carbohydrates consumption, and synthesis of heartwood substances. As the heartwood substances accumulated, basic density and essential oil content increased gradually, thereby Jiang Xiang was finally produced. In this process, physiological parameters of discolored sapwood gradually evolved to resemble those of natural heartwood. Hydrogen peroxide-induced Jiang Xiang was closest to natural heartwood, and the essential oil components met the standards for high-quality Jiang Xiang, while the induction effects of acetic acid and sodium chloride were unsatisfactory. Thus, this study indicates that hydrogen peroxide has the potential to induce Jiang Xiang production in Dalbergia odorifera.

Identification of Three Monofunctional Diterpene Synthases with Specific Enzyme Activities Expressed during Heartwood Formation in Western Redcedar (Thuja plicata) Trees.

Upon harvest, Western redcedar (WRC; Thuja plicata) trees have a high incidence and extent of heartwood rot. While monoterpenoids and lignans have been linked to rot resistance in this species, other specialized metabolites, such as diterpenes, are likely to contribute to rot resistance. Here we report the cloning and functional assessment of three putative diterpene synthase (TpdiTPS) genes expressed during heartwood formation in WRC. The predicted proteins of the three genes lack either of the two catalytically independent active sites typical of most diTPS, indicating monofunctional rather than bifunctional activity. To identify potential catalytic activities of these proteins, we expressed them in genetically engineered Escherichia coli strains that produce four potential substrates, geranylgeranyl diphosphate (GGDP), ent, syn, and normal stereoisomers of copalyl diphosphate (CDP). We found that TpdiTPS3 used GGDP to produce CDP. TpdiTPS2 used normal CDP to produce levopimaradiene. TpdiTPS1 showed stereoselectivity as it used normal CDP to produce sandaracopimaradiene and syn-CDP to produce syn-stemod-13(17)-ene. These genes and protein enzymatic activities have not been previously reported in WRC and provide an opportunity to assess their potential roles in heartwood rot resistance in this economically important species.

The chromosome-level draft genome of Dalbergia odorifera.

Background Dalbergia odorifera T. Chen (Fabaceae) is an International Union for Conservation of Nature red-listed tree. This tree is of high medicinal and commercial value owing to its officinal, insect-proof, durable heartwood. However, there is a lack of genome reference, which has hindered development of studies on the heartwood formation.FindingsWe presented the first chromosome-scale genome assembly of D. odorifera obtained on the basis of Illumina paired-end sequencing, Pacific Biosciences single-molecule real-time sequencing, 10x Genomics linked reads, and Hi-C technology. We assembled 97.68% of the 653.45 Mb D. odorifera genome with scaffold N50 and contig sizes of 56.16 and 5.92 Mb, respectively. Ten super-scaffolds corresponding to the 10 chromosomes were assembled, with the longest scaffold reaching 79.61 Mb. Repetitive elements account for 54.17% of the genome, and 30,310 protein-coding genes were predicted from the genome, of which ∼92.6% were functionally annotated. The phylogenetic tree showed that D. odorifera diverged from the ancestor of Arabidopsis thaliana and Populus trichocarpa and then separated from Glycine max and Cajanus cajan.ConclusionsWe sequence and reveal the first chromosome-level de novo genome of D. odorifera. These studies provide valuable genomic resources for the research of heartwood formation in D. odorifera and other timber trees. The high-quality assembled genome can also be used as reference for comparative genomics analysis and future population genetic studies of D. odorifera.

UPLC-ESI-MS/MS-Based Widely Targeted Metabolomics Analysis of Wood Metabolites in Teak (Tectona grandis).

The properties of teak wood, such as natural durability and beautiful color, are closely associated with wood extractives. In order to further understand the performance differences between teak heartwood and sapwood, we analyzed the chemical components of extractives from 12 wood samples using an ultrahigh-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS)-based metabolomics approach. In total, 691 metabolites were identified, and these were classified into 17 different categories. Clustering analysis and principal component analysis of metabolites showed that heartwood samples could be clearly separated from sapwood samples. Differential metabolite analysis revealed that the levels of primary metabolites, including carbohydrates, amino acids, lipids, and nucleotides, were significantly lower in the heartwood than in the sapwood. Conversely, many secondary metabolites, including flavonoids, phenylpropanoids, and quinones, had higher levels in the heartwood than in the sapwood. In addition, we detected 16 specifically expressed secondary metabolites in the heartwood, the presence of which may correlate with the durability and color of teak heartwood. Our study improves the understanding of differential metabolites between sapwood and heartwood of teak, and provides a reference for the study of heartwood formation.