Dalbergia odorifera T. Chen, an economically and medicinally valuable tree, suffers from heartwood shortage due to slow natural formation. Ethylene has emerged as a potent inducer of heartwood formation in D. odorifera, but long-term evidence and mechanisms remain unclear. To bridge this gap, we systematically assessed dynamic changes in morphology, anatomy, metabolomics and antimicrobial properties of ethylene-induced heartwood zone over 1, 3 and 5 years, comparing it with 20-year-old natural heartwood. Results showed that in the ethylene-stimulated zone, heartwood resins were initially deposited at the outermost layer and progressively infiltrated inward until full saturation. The coloration of induced heartwood zone gradually intensified, eventually developing hues and grain patterns resembling natural heartwood by 5 years. Heartwood extracts yield and antimicrobial activity matched natural heartwood after 1 year. Total flavonoid content matched natural heartwood by 3 years, with nine flavonoid components (e.g. naringenin, formononetin) governing color development. While volatile compounds composition matched natural heartwood after 5 years, flavonoid profiles remained distinct, indicating volatile compounds biosynthesis preceded flavonoids. More interestingly, this study proposed a novel hypothesis for heartwood formation: during natural heartwood development, a certain factor (e.g. ethylene) induces a transition zone containing numerous 'micro-zones,' where cell death and heartwood substance deposition progress gradually from the outer to inner layers. This pattern leaves residual sapwood within developing heartwood, effectively resolving the theoretical conflict regarding the presence of living cells in heartwood. Thus, this study not only confirms the long-term feasibility of ethylene-induced heartwood zone formation and its underlying mechanisms, but also proposes a groundbreaking hypothesis that challenges conventional understanding of heartwood formation, laying a crucial foundation for future research on heartwood formation mechanisms and targeted cultivation of high-value tree species.

Phosphorus (P) deficiency is a major nutritional constraint limiting the regeneration and large-scale cultivation of Homalium ceylanicum, a valuable tropical timber species in South and Southeast Asia. To identify an optimal P supply strategy for producing high-quality planting stock, we assessed the growth performance, photosynthetic characteristics, and nutrient status of one-year-old H. ceylanicum seedlings in response to exponential P fertilization at six levels: 0 (control), 25, 50, 100, 200 and 300 mg P per seedling. Seedlings supplied with 50 mg P per seedling performed best, with height, leaf biomass, and leaf area increasing by 57.5%, 152.0%, and 164.7%, respectively, relative to the unfertilized control. These enhancements were paralleled by significant improvements in net photosynthetic rate, chlorophyll content, photosystem II (PSII) photochemical efficiency, and gas exchange, indicating that enhanced photosynthetic carbon assimilation contributed to growth promotion. At the whole-plant level, this coordinated improvement in growth and photosynthesis was accompanied by a 171.04% increase in nitrogen (N) accumulation without inducing excessive P accumulation. In contrast, P supply above 100 mg per seedling reduced seedling height and root collar diameter, suppressed whole-plant biomass accumulation, and disrupted nutrient balance through excessive P accumulation and antagonistic effects on N and K (potassium). Vector analysis further confirmed 50 mg P per seedling as the optimal nutrient-loading dose, achieving effective P loading without inducing N or K excess or nutrient imbalance. In conclusion, exponential P fertilization at 50 mg P per seedling is a targeted nutritional strategy for producing high-quality planting stock, thereby supporting the plantation forestry of H. ceylanicum.

Agarwood is a valuable resinous aromatic substance known to have healing properties. Only plants in the Thymelaeace family, specifically the genera Aquilaria and Gyrinops, produce it to defend themselves from insect, bacterial, and fungal attacks. Over-harvesting of natural agarwood has given rise to different artificial agarwood induction techniques. However, the contribution of endophytic microorganisms in this process remains largely unknown. Herein, we employed fire drills and fire drill + brine treatments and investigated their impact on metabolite constituents and endophytes over time. Gas chromatography-mass spectrometry was used to examine the metabolites, and 16 S and ITS amplicon sequencing were applied to check for endophytes. Metabolites from each treatment were related to 16 S and ITS amplicon sequencing results from different times to find out what effect the treatments had and what role endophytes played in making agarwood. Fire drills with 50-80 ml of 0.4 mmol brine treatment resulted in the highest production of essential oil from agarwood, whereas fire drills with 50-80 ml of 4.0 mmol brine treatment produced the highest number of metabolites. Agarwood fragrant compounds such as chromones, sesquiterpenes, and agarotetrol were prominent among the differentially expressed metabolites and were positively associated with the abundance of bacterial endophytes Acidobacteriota, Chlamydiae, Bacteroidota, and Actinobacteria; and the fungal endophytes Rozellomycota, Basidiomycota, Aphelidiomycota, and Mortierellomycota. Saprotrophs and pathogens were prevalent in the treatment groups; however, with time, their proportion declined as Symbiotroph's proportion inclined, indicating successive roles of these fungi in agarwood induction and propagation. Among them, Acidobacteriota, Chlamydiae, Bacteroidota, and Actinobacteria bacterial; and Rozellomycota, Basidiomycota, Aphelidiomycota, and Mortierellomycota fungal endophytes are correlated with enhanced levels of essential agarwood fragrances such as Chromones, Sesquiterpenes, and Agarospirol. Our results show how important bacterial and fungal endophytes are for making agarwood. They also show how these endophytes change when interacting with the host plant after a fire drill and a brine treatment. A moderate brine concentration (0.4 mmol) following a fire drill can thus be employed as a sustainable agarwood production practice.

Drought has been found to affect the size and color of precious heartwood of Dalbergia odorifera, but the mechanism remains unclear. For this purpose, we performed the measurement of heartwood size, color and flavonoid content and composition in a 15-year-old mixed plantation of D. odorifera and Santalum album that had been subjected to two levels of rainfall exclusion and control treatments for 7 years, and carbon isotope labeling and anatomical observation in 2-year-old potted D. odorifera seedlings exposed to two levels of drought and control treatments. The field experiment showed that drought had significant effects on heartwood size and color of D. odorifera. More starch was depleted in the transition zone (TZ) in drought than in control. Drought significantly decreased the values of color parameters and increased the contents of total flavonoids, glycitein, fisetin, chrysin and claussequinone, and total flavonoids, glycitein, fisetin, chrysin and claussequinone were significantly negatively correlated with L* and b*. The pot experiment showed that during longitudinal transport of nonstructural carbohydrate (NSC), the dilution factor of 13C abundance in the inner bark sap in severe drought (SD) was twice as much as that in control. The inner bark thickness and transverse area of sieve tubes in SD were significantly lower than those in control. Our findings further confirm that drought promotes the heartwood formation of D. odorifera, and discuss interspecific variations in the response of heartwood formation to drought. Drought enhances the exchange transport of NSC between phloem and xylem by reducing the transverse area of sieve tubes, thus causing more NSC to be transported into xylem, and drought also promotes the depletion of starch in the TZ to produce more heartwood. Drought darkens the heartwood color by increasing the contents of total flavonoids, glycitein, fisetin, chrysin and claussequinone in heartwood. To our knowledge, this is the first study addressing the physiological and biochemical mechanism of drought regulating heartwood formation.

In recent years, some new “Qi-Nan” clones of Aquilaria sinensis with the characteristics of easy induction and high-quality agarwood have been obtained, through the cultivation and propagation of grafted seedlings. These clones are used for the intensive production of high-quality agarwood. The speed of resin formation and yield are crucial for the development of the agarwood industry. The differences in yield and chemical composition among different Qi-Nan clones and induction times are worth investigating. While the chemical composition differences between Qi-Nan and ordinary A. sinensis have been extensively studied, the effects of induction time coupled with different Qi-Nan clones on the chemical composition of Qi-Nan agarwood remain insufficiently explored. This study compared the changes in the chemical composition of four “Qi-Nan” clones of A. sinensis after 6, 12, and 24 months of induction through GC-QTOF-MS, the chemical composition and structure types of the four “Qi-Nan” clones were mainly 2-(2-phenylethyl)chromone derivatives (PECs) and Sesquiterpenoids (SESs), with the prolongation of induction time, the content of SESs increased, while the content of PECs decreased. Both the differences among clones and the induction time of “Qi-Nan” agarwood influence its chemical composition, which in turn affects the quality of the agarwood. Among these factors, induction time has a greater impact on the production of PECs in agarwood. The prolongation of induction significantly enhanced the yield of “Qi-Nan” agarwood and exhibited an inducing effect on the production of 2-(2-phenylethyl) chromone and 2-(2-4 phenylethyl)chromone. Compared with the agarwood obtained after 6 and 12 months of induction, the agarwood of “Qi-Nan” after 24 months of induction exhibited superior quality. The induction time for high-quality agarwood from the XGY clone was shorter (12 months) compared to the RH, YYZ, and AS clones (24 months). The study underscores that optimizing induction time and selecting suitable “Qi-Nan” clones can significantly enhance agarwood yield, quality, and production efficiency.

Agarwood is the resinous part of the injured tree of the Aquilaria species of the Thymelaeceae family, Qi-Nan is a type of agarwood that forms easily and benefits from a shortened inducing time, noted for features like its substantial resin, (2-phenylethyl) chromone and 2-[2-(4-methoxyphenyl) ethyl] chromone content. Although the content of agarotetrol in Qi-Nan is very low, it is still an important indicator for the agarwood quality. A validated method was developed to precisely quantify both agarotetrol and two aforementioned chromones, as well as ethanal extracts, within Qi-Nan to explore how the inducing time (half a year, one year, and two years) and different clones (YYZ, AS, RH, XGY) affect agarwood quality. Different clones and inducing time both have significant effects on agarwood quality. The agarwood quality of Qi-Nan does not necessarily improve with a longer inducing time. YYZ, AS, and RH clones reached to the best agarwood quality after two years of induction. The ethanol extracts content was among 46.82 ~ 48.59%, two chromones were among 10.57% ~ 14.05% after two years of induction. However, for XGY clone, the quality of agarwood after one year of induction was better than that after two years, which reached to the highest ethanol extracts (51.49%) and two chromones content reached to 12.43% and 12.91% after one year of induction. Therefore, for different clones of Qi-Nan, harvesting should be conducted at different time of induction for agarwood formations, which has theoretical implications for the cultivation and industrial development of cultivated Qi-Nan agarwood.

In recent years, some new Qi-Nan clones of Aquilaria sinensis, which have the characteristics of easily induced and high-quality agarwood, have been selected and propagated by grafting seedlings. To date, research on the grafting of Qi-Nan seedlings is limited. In this study, the effects of grafting on physiological characteristics and endophytic fungi of seedlings within a short period after grafting were studied by means of histochemical observations, physiological index determinations and Illumina sequencing. The results showed that the grafting healing time of ordinary A. sinensis was at least 10 days shorter than that of Qi-Nan, according to the degree of lignification of callus, and the tissue basis for the healing was the interxylary phloem. The MDA content of Qi-Nan peaked earlier than that of ordinary A. sinensis. The contents of JA and ABA peaked earlier in ordinary A. sinensis, and the SA content was significantly higher than that of Qi-Nan at 20–40 days; on average, it was 17.33% higher than that of Qi-Nan. A total of 5 phyla, 28 classes, 84 orders, 197 families, 489 genera and 842 species of endophytic fungi were identified before and after grafting. After grafting, the abundance and diversity of endophytic fungi in ordinary A. sinensis and Qi-Nan decreased, and the endophytic fungi were significantly different before and after grafting. In ordinary A. sinensis, before grafting, Dothideomycetes was the dominant class, and after grafting, Sordariomycetes was the dominant class. The dominant class of Qi-Nan before and after grafting was Dothideomycetes. The dominant genus of ordinary A. sinensis before grafting was Devriesia, and after grafting, it was Fusarium; that of Qi-Nan before grafting was Hyweljonesia and after grafting was Arthopyrenia. Functional genes of the endophytic fungi were mostly related to carbohydrate metabolism and energy metabolism, which may be the reason why endophytic fungi promote agarwood formation in Aquilaria trees. The findings suggest that the healing of the grafting interface in A. sinensis seedlings was the result of multiple factors, and endophytic fungi of Qi-Nan scion changed after grafting.

Agarwood is a highly sought-after resinous wood for use in medicine, incense, and perfume production. However, the process of agarwood formation is slow. In this study, the induction of agarwood formation in three-year-old Aquilaria sinensis “Qinan” trees through treatment with ethephon, hydrogen peroxide, sodium chloride, distilled water, and wounding was investigated. The results showed that the starch content significantly decreased and that the soluble sugar content significantly increased during the process of agarwood formation, with no significant difference between the different treatment groups. The net photosynthetic rate significantly decreased. Except for the sodium chloride treatment, the total antioxidant capacity and the contents of flavonoids and phenols significantly increased during the process of agarwood formation. The essential oil yield of the ethephon and hydrogen peroxide treatment groups was significantly higher than that of the other treatment groups, with the highest essential oil yield in the ethephon treatment group. Compared to the control group, salt treatment produced the lowest essential oil yield of agarwood. The results indicate that appropriate concentrations of ethephon and hydrogen peroxide can promote the formation of agarwood in A. sinensis “Qinan”.

The plastid is an essential organelle for its role in photosynthesis and energy production and its genomic information is always employed as important evolutionary markers to explore the relationship among species. Agarwood (Aquilaria), prized for its aromatic blend, finds extensive use in various cultures as incense and perfume. Despite its high economic importance, the phylogenetic status among Aquilaria based on plastomes remains ambiguous due to the lack of available plastomic resources. To bridge this knowledge gap, 22 Aquilaria plastomes were newly sequenced, similar variation patterns in this genus were determined, including a shared 16 bp extension of the rps19 gene and seven highly variable regions. The analysis highlighted the highest prevalence of the A/T motif among simple sequence repeats in these plastomes. Further phylogenetic analysis revealed Aquilaria's phylogenetic implications with an expanded dataset. This comprehensive plastomic resource not only enhances our understanding of Aquilaria evolution but also presents potential molecular markers for DNA barcoding.

Recently, some new Qi-Nan clones of Aquilaria sinensis (Lour.) Spreng which intensively produces high-quality agarwood have been identified and propagated through grafting techniques. Previous studies have primarily focused on ordinary A. sinensis and the differences in composition when compared to Qi-Nan and ordinary A. sinensis. There are few studies on the formation mechanism of Qi-Nan agarwood and the dynamic changes in components and endophytic fungi during the induction process. In this paper, the characteristics, chemical composition, and changes in endophytic fungi of Qi-Nan agarwood induced after 1 year, 2 years, and 3 years were studied, and Qi-Nan white wood was used as the control. The results showed that the yield of Qi-Nan agarwood continued to increase with the induction time over a period of 3 years, while the content of alcohol extract from Qi-Nan agarwood reached its peak at two years. During the formation of agarwood, starch and soluble sugars in xylem rays and interxylary phloem are consumed and reduced. Most of the oily substances in agarwood were filled in xylem ray cells and interxylary phloem, and a small amount was filled in xylem vessels. The main components of Qi-Nan agarwood are also chromones and sesquiterpenes. With an increasing induction time, the content of sesquiterpenes increased, while the content of chromones decreased. The most abundant chromones in Qi-Nan agarwood were 2-(2-Phenethyl) chromone, 2-[2-(3-Methoxy-4-hydroxyphenyl) ethyl] chromone, and2-[2-(4-Methoxyphenyl) ethyl] chromone. Significant differences were observed in the species of the endophytic fungi found in Qi-Nan agarwood at different induction times. A total of 4 phyla, 73 orders, and 448 genera were found in Qi-Nan agarwood dominated by Ascomycota and Basidiomycota. Different induction times had a significant effect on the diversity of the endophytic fungal community in Qi-Nan. After the induction of agarwood formation, the diversity of Qi-Nan endophytic fungi decreased. Correlation analysis showed that there was a significant positive correlation between endophytic fungi and the yield, alcohol extract content, sesquiterpene content, and chromone content of Qi-Nan agarwood, which indicated that endophytic fungi play a role in promoting the formation of Qi-Nan agarwood. Qi-Nan agarwood produced at different induction times exhibited strong antioxidant capacity. DPPH free radical scavenging activity and reactive oxygen species clearance activity were significantly positively correlated with the content of sesquiterpenes and chromones in Qi-Nan agarwood.

In recent years, plantations of Aquilaria sinensis in China have been dominated by Qi-nan, yet there remains limited research on the growth evaluation and breeding of these clones. In this study, a multi-point joint variance analysis, an additive main effect and multiplicative interaction (AMMI) model, a weighted average of absolute scores (WAASB) stability index, and a genotype main effect plus a genotype-by-environment interaction (GGE) biplot were used to comprehensively analyze the yield, stability, and suitable environment of 25 3-year-old Qi-Nan clones from five sites in southern China. The results showed that all the growth traits exhibited significant differences in the clones, test sites, and interactions between the clones and test sites. The phenotypic variation coefficient (PCV) and genetic variation coefficient (GCV) of the clones’ growth traits at the different sites ranged from 16.56% to 32.09% and 5.24% to 27.06%, respectively, showing moderate variation. The medium–high repeatability (R) of tree height and ground diameter ranged from 0.50 to 0.96 and 0.69 to 0.98, respectively. Among the clones, Clones G04, G05, G10, G11 and G13 showed good growth performance and could be good candidates for breeding. Environmental effects were found to be the primary source of variation, with temperature and light primarily affecting growth, while rainfall influenced survival and preservation rates. Yangjiang (YJ) was found to be the most suitable experimental site for screening high-yield and stable clones across the different sites, whereas the tree height and ground diameter at the Chengmai (CM) site were significantly higher than at the other sites, and the Pingxiang (PX) and Zhangzhou (ZZ) sites showed poor growth performance. The findings suggest that Qi-nan clones are suitable for planting in southern China. There were also abundant genetic variations in germplasm resources for the Qi-nan clones. The five selected clones could be suitable for extensive planting. Therefore, large-scale testing is necessary for determining genetic improvements in Qi-nan clones, which will be conducive to the precise localization of their promotion areas.

为探究降雨量和林分类型差异对植被多样性的影响,选取海南省年降雨量明显差异的3个地区设置植被多样性研究试验.经过2014—2019年连续5 a的调查发现,试验区天然林中现存植物种类共计45科58属61种,桉树人工林中有26科37属39种,芒果人工林、马占相思人工林、橡胶人工林由于频繁的人为经营管理,其植被多样性相对较低;不同降雨量地区天然林的物种多样性指数差异显著(P<0.05),桉树人工林则差异不显著;天然林和桉树人工林物种丰富度指数(R)随降雨量的增加而增加,天然林乔木层、灌木层的Shannon-Wiener多样性指数(H)、Simpson多样性指数(D)、Pielou均匀度指数(Jsw)随着降雨量增加而减小,草本层则与之相反;桉树人工林灌木层、草本层的Shannon-Wiener多样性指数、Simpson多样性指数、Pielou均匀度指数则随降雨量增加而增加;物种多样性指数的时间动态变化在天然林和桉树人工林灌木层和草本层波动明显,乔木层的变化则较为平稳.通过分析表明,降雨量是造成地区物种多样性差异的主要原因,与天然林相比,桉树人工林乔木层生态位的缺失是造成其植被多样性较低的主要原因,其他经济林分加之频繁的铲草施肥等人为经营措施而导致物种多样性更低.基于此,营建人工混交林或异龄林改造现有纯林促进人工林乔木层生态位的释放,同时改变其他经济林分经营模式是提高人工林物种多样性的关键.

Sandalwood is one of the most expensive woods in the world and is well known for its long-lasting and distinctive aroma. In our study, chromosome-level genome assemblies for two sandalwood species ( Santalum album and S antalum yasi ) were constructed by integrating NGS short reads, RNA-seq, and Hi-C libraries with PacBio HiFi long reads. The S. album and S. yasi genomes were both assembled into 10 pseudochromosomes with a length of 229.59 Mb and 232.64 Mb, containing 21,673 and 22,816 predicted genes and a repeat content of 28.93% and 29.54% of the total genomes, respectively. Further analyses resolved a Santalum -specific whole-genome triplication event after divergence from ancestors of the Santalales lineage Malania , yet due to dramatic differences in transposon content, the Santalum genomes were only one-sixth the size of the Malania oleifera genome. Examination of RNA-seq data revealed a suite of genes that are differentially expressed in haustoria and might be involved in host hemiparasite interactions. The two genomes presented here not only provide an important comparative dataset for studying genome evolution in early diverging eudicots and hemiparasitic plants but will also hasten the application of conservation genomics for a lineage of trees recovering from decades of overexploitation.

[目的]探究盐胁迫对土沉香中沉香四醇及2-(2-苯乙基)色酮的诱导作用.[方法]在传统冷钻和火钻的基础上增加盐(质量分数26％NaCl)胁迫,设冷钻、冷钻+盐、火钻、火钻+盐4个处理,结香10个月后,使用体积分数95％乙醇对各处理沉香样品进行超声提取得到醇提物,采用气相色谱-质谱(GC-MS)联用法对沉香的化学成分进行定性分析,使用超高效液相色谱串联三重四级杆质谱仪(UPLC-MS-MS),测定其中沉香四醇及2-(2-苯乙基)色酮的绝对含量.[结果]①冷钻和火钻结合盐处理后,沉香醇提物含量均不同程度提升,其中冷钻+盐处理醇提物含量较冷钻处理提高21.43％,火钻+盐处理醇提物含量较火钻处理提高64.86％.②与冷钻和火钻处理相比,加盐处理后沉香中化合物种类总数未增加,冷钻和冷钻+盐处理化合物种类为35种,火钻和火钻+盐处理化合物种类为46种;冷钻+盐处理倍半萜类和色酮类物质种类与冷钻处理相比均未增加,火钻+盐处理倍半萜类化合物较火钻处理增加1种,色酮类化合物较火钻处理增加4种;加盐处理后沉香中倍半萜类物质相对含量减少,色酮类物质相对含量增加,冷钻处理、冷钻+盐处理、火钻处理、火钻+盐处理沉香中倍半萜类物质相对含量分别为88.67％,75.34％,56.72％和54.31％,色酮类物质相对含量分别为8.74％,20.96％,27.05％和43.24％.③冷钻+盐处理沉香中沉香四醇、2-(2-苯乙基)色酮含量分别为1.08和0.14 mg/g,是冷钻处理(0.37和0.01 mg/g)的2.92和13.18倍;火钻+盐处理沉香中沉香四醇、2-(2-苯乙基)色酮含量分别为2.93和0.68 mg/g,是火钻处理(1.22和0.07 mg/g)的2.42和9.90倍.[结论]盐胁迫显著提升了沉香醇提物含量,增加了火钻处理的倍半萜类和色酮类物质种类,且对沉香四醇和2-(2-苯乙基)色酮的产生有诱导作用.

ObjectiveAquilaria sinensis ‘Qi Nan’ clones belong to Aquilaria sinensis, which has the characteristics of easier induced agarwood, and different strains of A. sinensis ‘Qi Nan’ clones have different environmental adaptability to the same region. In order to understand the growth status of 26 A. sinensis ‘Qi Nan’ clones in Chaozhou, Guangdong, and then select excellent A. sinensis ‘Qi Nan’ clones suitable for promotion and cultivation.Method26 A. sinensis ‘Qi Nan’ clones were used as research materials for this study. The growth traits and photosynthetic physiological characteristics of the 1-year-old experimental forest were investigated, and the differences and correlations between various indicators among different strains were analyzed. Cluster analysis method were used to screen for the clones with excellent growth performance.ResultThere were significant differences in seedling height, preservation rate, ground diameter, crown width, and photosynthetic physiological indicators among the 26 A. sinensis ‘Qi Nan’ clones. The variation range of preservation rate was 44.4%-92.2%, with the highest preservation rate of Diao YW and the lowest of Xiang SYH having; The variation range of seedling height was 103-174 cm, the variation range of ground diameter was 18.5-36.1 mm, and the variation range of crown width was 43-94 cm. The values of seedling height, ground diameter, and crown width in Jin SY were the highest, while it was the lowest in Bo LZ. Correlation analysis showed a highly significant positive correlation between ground diameter and seedling height (P < 0.01), and a significant positive correlation between ground diameter and crown diameter (P < 0.05), and a highly significant positive correlation between crown diameter and survival rate (P < 0.01). Cluster analysis clustered 26 A. sinensis ‘Qi Nan’ clones into three categories. The second category had the best growth, with survival rates and seedling heights above 83.3% and 144 cm, respectively, including Diao YW, Lan BS, Jin SZ, Jin SY, and Xiang J. The third category had the worst growth, with preservation rates and seedling heights below 64% and 130 cm, respectively, including Xiang SYH, Xi GY, You YZ, Hong GJY and Bo LZ. The first category had a moderate growth, with survival rates and seedling heights between the second and third categories.ConclusionDiao YW, Lan BS, Jin SZ, Jin SY and Xiang J from 26 A. sinensis ‘Qi Nan’ clones with fast growth rates and high survival rates in this study, which were suitable for promotion and planting in Chaozhou.

为筛选适合广东潮州地区推广种植的优良奇楠沉香品系Aquilaria sinensis'Qi Nan',选择已推广种植的13个品系,测定定植1年后树高、地径、冠幅和保存率等生长指标.结果表明:不同奇楠沉香品系间保存率差异达极显著水平(P<0.001),蓝宝石、金丝油、凹身对试验区的环境适应能力较强,保存率较高,西瓜叶、波浪仔保存率较低,在该地适应能力较差.不同品系的树高、地径、冠幅和高径比的差异均极显著(P<0.001).通过系统聚类分析,可分为3个类群,A类群为金丝油,生长速度较快,B类群为红骨尖叶和波浪仔,生长缓慢,其他品系为C类,生长速度适中.综合早期生长性状,金丝油生长速度快,保存率高,适应性强,适合在潮州地区推广种植;红骨尖叶和波浪仔,保存率低,生长速度慢,不宜于潮州地区大面积推广种植.

ObjectiveTo screen out a method which can not only effectively promote the agarwood formation, but also ensure the growth of Aquilaria sinensis tree.MethodIn this study, 12 kinds of treatments that belong to three categories (T1, T2 and T3) of plant growth regulator mixture (MeJA, ABA, 6-BA and ETH) (T1), inorganic salts mixture (NaCl, FeCl2 and NaHSO3) (T2) and fungi (Trichoderma atroviride, Fusarium solani, Botryosphaeria rhodina, Lasiodiplodia theobrome) (T3) were used to manually instill 8-year-old A. sinensis tree. The following indexes, contained that the growth of tree (diameter at breast height (DBH), height and crown width) and the agarwood formation (alcohol-soluble extractive content, maximum area and length) were analyzed.ResultIn terms of growth, all treatments had significant effect on the growth of DBH, and had no significant effect on tree height and crown width. Among them, the mass concentrations of T1 components at 1, 0.01, 0.5 and 0.05 mg·g-1 (3, treatment number, the same below), T2 components at 3, 20, 10 mg·g-1 (7) and B. rhodina (11) had the least effect on the growth of DBH. In terms of agarwood formation, the alcohol-soluble extract content of agarwood increased significantly when the mass concentrations of T1 components were 0.5, 1, 0.05, 1 mg·g-1 (2), T2 components were 1, 2.5, 5 mg·g-1 (6), respectively, and the fungi was F. solani in T3 (10). At the same time, the agarwood area and the length of No.6 and No.10 treatments were the highest among groups. The correlation analysis of each index showed that there was a negative correlation between the growth and agarwood formation indexes of A. sinensis under different treatment conditions. The result of principal component weighted analysis showed that the comprehensive scores of No.6 and 10 treatments ranked first and second respectively, which not only effectively induced agarwood formation, but also had little impact on the growth of A. sinensis tree.ConclusionTwelve methods of artificial induction can promote the agarwood formation of A. sinensis trees, but slow down the growth of trees, so agarwood formation is the result of the tradeoff between tree growth and defense.

Regulation of abscisic acid (ABA) biosynthesis helps plants adapt to drought stress, but the underlying molecular mechanisms are largely unclear. Here, a drought-induced transcription factor XsAGL22 was isolated from yellowhorn (Xanthoceras sorbifolium Bunge). Yeast one-hybrid and electrophoretic mobility shift assays indicated that XsAGL22 can physically bind to the promoters of the ABA biosynthesis-related genes XsNCED6 and XsBG1, and a dual-luciferase assay showed that XsAGL22 activates the promoters of the later two genes. Transient overexpression of XsAGL22 in yellowhorn leaves also increased the expression of XsNCED6 and XsBG1 and increased cellular ABA levels. Finally, heterologous overexpression of XsAGL22 in poplar increased ABA content, reduced stomatal aperture and increased drought resistance. Our results suggest that XsAGL22 is a powerful regulator of ABA biosynthesis and plays a critical role in drought resistance in plants.

Agarwood is the dark resinous heartwood of injured ordinary Aquilaria sinensis (OA). Recently, some new clones of A. sinensis (Qi-Nan) that intensively produce high-quality agarwood were selected and cultivated by grafted clonal seedlings. However, very little is known about their agarwood formation mechanism, and it is unclear whether the current method of distinguishing Qi-Nan from OA by observing its leaf apparent morphology is scientifically reliable. In this study, the differences between OA and Qi-Nan clones in agarwood formation and their correlation with morphological, anatomical and physiological characteristics were investigated in two types of A. sinensis trees. After the mechanical injury, agarwood yield and essential oil content in agarwood of Qi-Nan were significantly higher than that of OA. There was no significant difference in leaf shape parameters between Qi-Nan and OA, but Qi-Nan showed higher specific leaf weight, total leaf chlorophyll, leaf nitrogen content and net photosynthetic rate. A xylem anatomical analysis showed that Qi-Nan had significantly smaller vessel wall thickness, greater ray cell wall thickness and larger interxylary phloem area than OA. Moreover, Qi-Nan had a greater consumption of non-structural carbohydrates than OA. Agarwood yield and oil content in agarwood showed significantly positive correlations with leaf photosynthetic capacity, the wall thickness of xylem ray cell, interxylary phloem area, starch utilization rate of trees, and a significantly negative correlation with the wall thickness of xylem vessel of trees. In brief, Qi-Nan has a stronger photosynthetic basis to supply more carbon sources, a more efficient xylem structural basis for agarwood production and a higher carbon source utilization rate, leading to a higher agarwood yield and oil content. It is not reliable to distinguish Qi-Nan from OA simply by observing leaf apparent morphology.

Santalum album is a semi parasitic plant and its growth is often restricted due to a lack of a host or water during plantation establishment. In this study, the effects of water and the host on the growth of S. album seedlings were studied in pot culture. The results showed that the net photosynthetic rate and height of S. album seedlings decreased significantly under drought stress. Compared with the seedlings of S. album grown without a host, the host could significantly increase the growth of S. album seedlings. The contents of soluble sugar and proline in S. album leaves increased significantly under drought stress. Drought stress resulted in a significant accumulation of malondialdehyde, increments of antioxidant enzymes activity, and non-enzymatic antioxidant substances. Antioxidant capacity was stronger and malondialdehyde content was lower in the seedling leaves of S. album with a host than in the seedlings without a host. RNA-seq was used to analyze the transcription expression profiles of S. album leaves and the results were consistent with the physiological data. These results indicate that the host can promote the seedling growth of S. album and it can increase the antioxidant capacity and osmotic adjustment substance content of the seedlings of S. album, alleviating the damage caused by drought.