Sinensis Trees Research Articles

3D documentation and classification of incense tree Aquilaria sinensis (Lour.) Spreng. wounds by photogrammetry and its potential conservation applications.

In recent years, illegal felling of and damage to the incense tree Aquilaria sinensis (Lour.) Spreng. have been reported in Hong Kong. Their native populations are under increasingly severe threat. Therefore, the development of a standard and efficient method to classify and document wounds on vulnerable trees is urgently needed for conservation purposes. In this study, photogrammetry was used to document wounds in A. sinensis through 3D modeling. A total of 752 wound records from 484 individual A. sinensis trees from Hong Kong were included to establish a new wound classification system. Our major findings include a novel standardized procedure for photogrammetric documentation and a wound classification system. The results of this study will facilitate A. sinensis conservation, by enhancing wound documentation and information transfer to law enforcement and education.

Salty treatment increased bioactive compounds accumulation during agarwood development in Aquilaria sinensis trees

To compare the bioactive compounds in agarwood induced by different methods in Aquilaria sinensis(Lour.) Gilg trees, a two dimensional thin layer chromatograph(2D-TLC) combined with effect directive analysis(EDA) was developed. Three antioxidants were found by 2D-TLC-DPPH and further identified as 2-(2-phenylethyl) chromones(PECs) with LC-MS/MS. The 3 antioxidants decreased along agarwood formation and their compositions in drilling induced agarwood differed with those in microbe culture induced agarwood. Further study showed NaCl treatment promoted antioxidants accumulation in agarwood induced by drilling or hot drilling. Hot drilling combined with salty stimulation was most efficient in some chemicals accumulation, which were identified as PECs with antioxidant, tyrosinase or β-glucosidase inhibiting activities by 2D-TLC-EDA-LC-MS/MS. This study provided a 2D-TLC-EDA-LC-MS/MS method for bioactive compounds screen and qualification of agarwood. Based on this method, non-conventional methods were found to accelerate the accumulation of some bioactive PECs in A. sinensis trees.

Effects of Different Levels of Physical Damage Combined with Fungal Induction on Agarwood Formation

As wild Aquilaria sinensis resources are exhausted and protected, China has established a huge number of plantations of Aquilaria trees and developed artificial induction techniques. However, the current output and quality of artificial induction technology have not yet met the expected results. It has been found that high-oil-containing agarwood may contain particular fungal stains associated with agarwood production. To enhance the quality of agarwood, we recovered and characterized three highly active fungi from high-oil-containing agarwood and inoculated them onto A. sinensis trees using two traditional physical methods. The results showed that fungi extracted from high-oil-containing agarwood can effectively increase the yield and quality of agarwood. During the agarwood formation process, parenchyma cells, xylem rays, and axial parenchyma cells in the xylem gradually undergo apoptosis, thereby promoting the expansion of the color range of agarwood. Nine months after the treatment, the alcohol-soluble extract content in agarwood reached the standard specified in the Chinese Pharmacopoeia (10%), and the proportions of sesquiterpenes and chromones in each treatment were 55.82%, 58.31%, 62.65%, 70.97%, and 13.71%, respectively. These results indicate that fungal induction has a positive impact on the quality of agarwood. In addition, compared to drilling and fungus combined induction, “burning holes and fungi” combined induction demonstrates better results and can further improve the yield and quality of agarwood.

Isolation and screening of fungi for enhanced agarwood formation in Aquilaria sinensis trees.

Agarwood is a resinous heartwood of Aquilaria sinensis that is formed in response to mechanical wounding. In the present study pre-treatment of Aquilaria sinensis was carried out, and then the dominant fungi were isolated and purified from the surface and electroshock holes of trees. The isolated Trichoderma sp. and Neurospora sp. were then screened for resistance against benzyl acetone and then inoculated into healthy Aquilaria sinensis trees. After six months, the agarwood was collected for analysis. The chemical composition of incense was analyzed using gas chromatography-mass spectroscopy, and 82 chemical constituents were identified. Agarwood products formed by using Trichoderma sp. and Neurospora sp. consisted of 50.22% and 48.71% ether extracts, respectively, which surpassed the 10% threshold specified by the Chinese Pharmacopoeia. Similarly, relative aromatic contents in the two agarwood products were 30.1% and 32.86%, while proportions of sesquiterpene constituents were 10.21% and 11.19%, respectively. These two agarwood-specific chemical constituents accounted for a large proportion of the total chemical composition, which showed that the generated agarwood was of good quality. The results of the study revealed that both Trichoderma sp. and Neurospora sp. were able to effectively induce agarwood production in Aquilaria sinensis trees in 6 months. This study expands the library of fungi that promote the production of agarwood from Aquilaria sinensis trees.

Barrier zone formation and development in the stems of Aquilaria sinensis (Thymelaeaceae) and the effect on agarwood formation

Summary Barrier and reaction zones are core parts of compartmentalization in trees. However, little is known about the relationship between them. Here, agarwood and barrier zone formation in Aquilaria sinensis trees were studied for the first time using compartmentalization theory. The main results were as follows: (1) Wounding methods had a very important influence on the occurrence of barrier zones in A. sinensis. (2) The barrier zone development process was divided into three phases based on the morphological features. (3) The agarwood resin mainly accreted during the barrier zone lag and division phases; then, after the barrier zone entered the differentiation phase, the resin no longer accreted and even tended to degrade. (4) In the application of the whole-tree agarwood-inducing technique, the barrier zone generally began to appear 10 months after the technique treatment, and the barrier zones were more severe in the lower part of the stem. (5) Considering the agarwood yield, agarwood resin filling degree and ethanol-soluble extract content, the serious barrier zone indeed reduced the agarwood productivity. This study is important for revealing the agarwood and barrier zone formation mechanism in Aquilaria trees. It also provides a good research model for considering the high economic value of agarwood when studying compartmentalization.

Wound-Induced Temporal Reprogramming of Gene Expression during Agarwood Formation in Aquilaria sinensis.

Agarwood is a resinous heartwood of Aquilaria sinensis that is formed in response to mechanical wounding. However, the transcriptional response of A. sinensis to mechanical wounding during the agarwood formation process is still unclear. Here, three five-year-old A. sinensis trees were mechanically damaged by a chisel, and time-series transcriptomic analysis of xylem tissues in the treated area (TA) was performed at 15 (TA1), 70 (TA2) and 180 days after treatment (TA3). Samples from untreated areas at the corresponding time points (UA1, UA2, UA3, respectively) were collected as controls. A total of 1862 (TA1 vs. UA1), 961 (TA2 vs. UA2), 1370 (TA3 vs. UA3), 3305 (TA2 vs. TA1), 2625 (TA3 vs. TA1), 2899 (TA3 vs. TA2), 782 (UA2 vs. UA1), 4443 (UA3 vs. UA1) and 4031 (UA3 vs. UA2) genes were differentially expressed (DEGs). Functional enrichment analysis showed that DEGs were significantly enriched for secondary metabolic processes, signal transduction and transcriptional regulation processes. Most of the genes involved in lignin biosynthesis were more abundant in the TA groups, which included phenylalanine ammonia-lyase, 4-coumarate CoA ligase, cinnamate 4-hydroxylase, caffeoyl-CoA O-methyltransferase and cinnamoyl-CoA reductase. DEGs involved in sesquiterpene biosynthesis were also identified. Hydroxymethylglutaryl-CoA synthase, 3-hydroxy-3-methylglutaryl-coenzyme A reductase, phosphomevalonate kinase and terpene synthase genes were significantly increased in the TA groups, promoting sesquiterpene biosynthesis in the wounded xylem tissues. The TF-gene transcriptomic networks suggested that MYB DNA-binding, NAM, WRKY, HLH and AP2 TFs co-expressed with genes related to lignin and sesquiterpene synthesis, indicating their critical regulatory roles in the biosynthesis of these compounds. Overall, our study reveals a dynamic transcriptional response of A. sinensis to mechanical wounding, provides a resource for identifying candidate genes for molecular breeding of agarwood quality, and sheds light on the molecular mechanisms of agarwood formation in A. sinensis.

Characteristic quality analysis for biologically induced agarwood columns in Aquilaria sinensis

Current artificial agarwood-inducing techniques yield low quality and quantities of agarwood. On account of unclear agarwood formation mechanism there's still no high-efficiency agarwood inducing method globally spread. In this study, a complete agarwood column was taken out of the live tree trunk at 6 months post-treatment by a novel agarwood-inducing method (Agar-Bit) in cultivated Aquilaria sinensis trees, and was first divided into 8 parts (A1-4, B1-4) involving agarwood layer (A part) and brown inner layer (B part) according to its color and length for analysis. These eight parts were analyzed microscope observation, 6 chromones' contents and characteristic chromatograms by HPLC (high performance liquid chromatography), GC-MS (gas chromatography-mass spectrometer) with to determine chemical changes. Other quality characteristics, TLC (thin-layer chromatography) and alcohol soluble extraction content, were also determined. Our results showed that resin changed with A to B part and microstructure changed with length. Six chromones in the eight parts varied with layers. Result of characteristic chromatograms showed that both A and B parts contained six characteristic peaks. Volatile component distributed mainly in A part, but important chromones were also detected in B parts. Results from TLC and alcohol soluble extraction content also showed that B part contained characteristic compounds of agarwood. In addition, some compounds in the essential oil detected by GC-MS in A part produced by Agar-Bit were similar to that found in natural agarwood, compounds in B parts were similar to BC agarwood, as were the results for the TLC and alcohol soluble extraction content. In conclusion, the chemical distribution obtained here from Agar-Bit could provide some clues to optimize high production and high efficiency stimulating method for whole tree full of resin in Aquilaria sinensis and to reveal the subtle agarwood formation mechanism throughout a whole trunk.

The key odor-active components differed in cultured agarwood from two germplasms of Aquilaria. sinensis trees

To tentatively identify the key odor-active components and compare the odor profiles of cultured agarwood from ordinary and Qi-Nan Aquilaria. sinensis trees, headspace solid-phase microextraction gas chromatography-olfactometry-mass spectrometry (HS-SPME-GC–O–MS) coupled with aroma extraction dilution analysis (AEDA) were used to analyze ordinary(OA)and Qi-Nan agarwood(QNA) compared to non-resinous whitewood. From the 61 odorants found in agarwood, 20 key odor-active components were screened with flavor dilution (FD)≥ 3. Among them, FDs of cis-Eudesm-6-en-11-ol，(E)-isovalencenal and guaiol in OA were higher than those in QNA, which explained for the odor profile of stronger floral and sweet attributes in OA group at ambient temperature. When temperature became higher, low molecular weight aromatic compounds increased greatly and further differed OA and QNA. For the 2-(2-Phenylethyl) chromone derivatives(PECs)in QNA and OA were distinct and consequently pyrolyzed into different aromatic compounds. The results strongly suggested QNA and OA maintained different odor-active components, which lead to their own unique odor profiles.

Comparative Morphological, Anatomical and Physiological Analyses Explain the Difference of Wounding-Induced Agarwood Formation between Ordinary Agarwood Nongrafted Plants and Five Grafted Qi-Nan Clones (Aquilaria sinensis)

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.

Comparative transcriptome analysis reveals different defence responses during the early stage of wounding stress in Chi-Nan germplasm and ordinary Aquilaria sinensis

BackgroundAgarwood is a valuable Chinese medicinal herb and spice that is produced from wounded Aquilaria spp., is widely used in Southeast Asia and is highly traded on the market. The lack of highly responsive Aquilaria lines has seriously restricted agarwood yield and the development of its industry. In this article, a comparative transcriptome analysis was carried out between ordinary A. sinensis and Chi-Nan germplasm, which is a kind of A. sinensis tree with high agarwood-producing capacity in response to wounding stress, to elucidate the molecular mechanism underlying wounding stress in different A. sinensis germplasm resources and to help identify and breed high agarwood-producing strains.ResultsA total of 2427 and 1153 differentially expressed genes (DEGs) were detected in wounded ordinary A. sinensis and Chi-Nan germplasm compared with the control groups, respectively. KEGG enrichment analysis revealed that genes participating in starch metabolism, secondary metabolism and plant hormone signal transduction might play major roles in the early regulation of wound stress. 86 DEGs related to oxygen metabolism, JA pathway and sesquiterpene biosynthesis were identified. The majority of the expression of these genes was differentially induced between two germplasm resources under wounding stress. 13 candidate genes related to defence and sesquiterpene biosynthesis were obtained by WGCNA. Furthermore, the expression pattern of genes were verified by qRT-PCR. The candidate genes expression levels were higher in Chi-Nan germplasm than that in ordinary A. sinensis during early stage of wounding stress, which may play important roles in regulating high agarwood-producing capacity in Chi-Nan germplasm.ConclusionsCompared with A. sinensis, Chi-Nan germplasm invoked different biological processes in response to wounding stress. The genes related to defence signals and sesquiterepene biosynthesis pathway were induced to expression differentially between two germplasm resources. A total of 13 candidate genes were identified, which may correlate with high agarwood-producting capacity in Chi-Nan germplasm during the early stage of wounding stress. These genes will contribute to the development of functional molecular markers and the rapid breeding highly of responsive Aquilaria lines.

Identification of sesquiterpene synthase genes in the genome of Aquilaria sinensis and characterization of an α-humulene synthase

Sesquiterpenes are the major pharmacodynamic components of agarwood, a precious traditional Chinese medicine obtained from the resinous portions of Aquilaria sinensis trees that form in response to environmental stressors. To characterize the sesquiterpene synthases responsible for sesquiterpene production in A. sinensis, a bioinformatics analysis of the genome of A. sinensis identified six new terpene synthase genes, and 16 sesquiterpene synthase genes were identified as type TPS-a in a phylogenetic analysis. The expression patterns for eight of the sesquiterpene synthase genes after treatment with various hormones or hydrogen peroxide were analyzed by real-time quantitative PCR. The results suggest that 100 μM methyl jasmonate, ethephon, ( ±)-abscisic acid or hydrogen peroxide could be effective short-term effectors to increase the expression of sesquiterpene synthase genes, while 1 mM methyl salicylate may have long-term effects on increasing the expression of specific sesquiterpene synthase genes (e.g., As-SesTPS, AsVS, AsTPS12 and AsTPS29). The expression changes in these genes under various conditions reflected their specific roles during abiotic or biotic stresses. Heterologous expression of a novel A. sinensis sesquiterpene synthase gene, AsTPS2, in Escherichia coli produced a major humulene product, so AsTPS2 is renamed AsHS1. AsHS1 is different from ASS1, AsSesTPS, and AsVS, for mainly producing α-humulene. Based on the predicted space conformation of the AsHS1 model, the small ligand molecule may bind to the free amino acid by hydrogen bonding for the catalytic function of the enzyme, while the substrate farnesyl diphosphate (FPP) probably binds to the free amino acid on one side of the RxR motif. Arg450, Asp453, Asp454, Thr457, and Glu461 from the NSE/DTE motif and D307 and D311 from the DDxxD motif were found to form a polar interaction with two Mg2+ clusters by docking. The Mg2+-bound DDxxD and NSE/DTE motifs and the free RXR motif are jointly directed into the catalytic pocket of AsHS1. Comparison of the tertiary structural models of AsHS1 with ASS1 showed that they differed in structures in several positions, such as surrounding the secondary catalytic pocket, which may lead to differences in catalytic products. Based on the results, biosynthetic pathways for specific sesquiterpenes such as α-humulene in A. sinensis are proposed. This study provides novel insights into the functions of the sesquiterpene synthases of A. sinensis and enriches knowledge on agarwood formation.

Substrate pH Influences the Nutrient Absorption and Rhizosphere Microbiome of Huanglongbing-Affected Grapefruit Plants

The substrate pH directly affects nutrient availability in the rhizosphere and nutrient uptake by plants. Macronutrients such as nitrogen, potassium, calcium, magnesium, and sulfur are highly available at pH 6.0–6.5, while micronutrients become less available at higher, alkaline pH (pH > 7.0). Recent research has indicated that low pHs can enhance nutrient uptake and improve sweet orange (Citrus sinensis) tree health. We designed a study to understand the influence of a wide range of substrate pH values on plant size and biomass, nutrient availability, leaf gas exchange, and rhizosphere microbiome of grapefruit (Citrus paradisi) affected by Huanglongbing (HLB). Two-year-old “Ray Ruby” grapefruit plants grafted on sour orange (Citrus aurantium) rootstock were cultivated indoors in 10-cm wide × 40-cm tall pots with peat:perlite commercial substrate (80:20 v/v). We tested two disease statuses [HLB-free or healthy (negative, HLB–) and HLB-affected (positive, HLB+)] and six substrate pH values (4, 5, 6, 7, 8, 9) in a 2 × 6 factorial arranged on a complete randomized design with four replications. The canopy volume of HLB+ plants was 20% lower than healthy plants, with pHs 7 and 9 resulting in 44% less canopy volume. The root and shoot ratio of dry weight was 25.8% lower in HLB+ than in healthy plants. Poor root growth and a decrease in fibrous roots were found, especially in pH 5 and 6 treatments in HLB+ plants (p < 0.0001). The disease status and the substrate pHs influenced the leaf nutrient concentration (p < 0.05). High substrate pH affects nutrient availability for root uptake, influencing the nutrient balance throughout the plant system. pH values did not affect plant photosynthesis, indicating that pH does not recover HLB+ plants to the photosynthetic levels of healthy plants—even though high pH positively influenced internal CO2. There were collectively over 200 rhizobacterial identified by the 16S rRNA gene sequencing in individual phylogenetic trees. Most rhizobacteria reads were identified in pH 9. Our results indicated no effect of substrate pHs on the plant disease status induced by enhanced nutrient uptake.

Transcriptomic and physiological analysis reveals interplay between salicylic acid and drought stress in citrus tree floral initiation.

Salicylic acid (SA) and drought stress promote more flowering in sweet orange. The physiological response and molecular mechanism underlying stress-induced floral initiation were discovered by transcriptome profiling. Numerous flowering-regulated genes were identified, and ectopically expressed CsLIP2A promotes early flowering in Arabidopsis. Floral initiation is a critical developmental mechanism associated with external factors, and citrus flowering is mainly regulated by drought stress. However, little is known about the intricate regulatory network involved in stress-induced flowering in citrus. To understand the molecular mechanism of floral initiation in citrus, flower induction was performed on potted Citrus sinensis trees under the combined treatment of salicylic acid (SA) and drought (DR). Physiological analysis revealed that SA treatment significantly normalized the drastic effect of drought stress by increasing antioxidant enzyme activities (SOD, POD, and CAT), relative leaf water content, total chlorophyll, and proline contents and promoting more flowering than drought treatment. Analysis of transcriptome changes in leaves from different treatments showed that 1135, 2728 and 957 differentially expressed genes (DEGs) were revealed in response to DR, SD (SA + DR), and SA (SA + well water) treatments in comparison with the well watered plants, respectively. A total of 2415, 2318 and 1933 DEGs were expressed in DR, SD, and SA in comparison with water recovery, respectively. Some key flowering genes were more highly expressed in SA-treated drought plants than in DR-treated plants. GO enrichment revealed that SA treatment enhances the regulation and growth of meristem activity under drought conditions, but no such a pathway was found to be highly enriched in the control. Furthermore, we focused on various hormones, sugars, starch metabolism, and biosynthesis-related genes. The KEGG analysis demonstrated that DEGs enriched in starch sucrose metabolism and hormonal signal transduction pathways probably account for stress-induced floral initiation in citrus. In addition, a citrus LIPOYLTRANSFERSAE 2A homologous (LIP2A) gene was upregulated by SD treatment. Ectopic expression of CsLIP2A exhibited early flowering in transgenic Arabidopsis. Taken together, this study provides new insight that contributes to citrus tree floral initiation under the SA-drought scenario as well as an excellent reference for stress-induced floral initiation in woody trees.

Transcriptomic Response of Huanglongbing-Infected Citrus sinensis Following Field Application of a Microbial Fermentation Product.

Huanglongbing (HLB) is considered the most destructive disease in Citrus production and threatens the future of the industry. Microbial-derived defense elicitors have gained recognition for their role in plant defense priming. This work assessed a 5% (V/V) microbial fermentation application (MFA) and its role in the elicitation of defense responses in HLB-infected Citrus sinensis trees following a foliar application with a pump sprayer. Using a PCR detection method, HLB infection levels were monitored in healthy and infected trees for 20months. Nutrient analysis assessed N, P, K, Ca, Mg, Mn, Zn, Fe, B, and Cu concentrations in the trees. MFA significantly increased Cu concentrations in treated trees and resulted in the stabilization of disease index (DI) in infected trees. Initial real-time qPCR analysis of defense-associated genes showed a significant increase in pathogenesis-related protein 2 (PR2) and phenylalanine ammonia lyase (PAL) gene expression in healthy and HLB-infected trees in response to MFA. Gene expression of PR2 and PAL peaked 6h post-microbial fermentation application during an 8-h sampling period. A transcriptomic assessment using GeneChip microarray of the hour 6 samples revealed differential expression of 565 genes when MFA was applied to healthy trees and 909 genes when applied infected citrus trees when compared to their respective controls. There were 403 uniquely differentially expressed genes in response to MFA following an intersectional analysis of both healthy and infected citrus trees. The transcriptomic analysis revealed that several genes associated with plant development, growth, and defense were upregulated in response to MFA, including multiple PR genes, lignin formation genes, ROS-related genes, hormone synthases, and hormone regulators. This study provides further evidence that MFA may play an important role as a plant elicitor in an integrated pest management strategy in citrus and other agronomically important crops.

Structural analysis of silicon carbide prepared from two types of carbon sources

Silicon carbide (SiCcs and SiCdk) powders have been prepared from Murzuq silica sand (fine silica) as a silica source(Mws), citrus Sinensis tree branches (cs), and dates kernels (dk) taken as carbon sources for industrial applications. The sol–gel method was employed to prepare the samples. The samples were calcinated in a bath containing silica/carbon mixture for 6 h. The X-ray diffraction (XRD) results revealed that both samples with different carbon sources contained three polytypes of 6H, 21R, and 3C-SiC. The morphology of the samples has been measured using the field emission scanning microscope (FE-SEM). Large particles accompanied by thin rod-like structures with average lengths between 0.3 and 2 μm were observed for the SiCcs sample. The morphology of the SiCdk sample showed large particles and some holes. Raman spectra of both samples showed peaks located at 1356 cm−1 and 1596 cm−1 related to D and G peaks, respectively.

Insights into the phase evolution-composition-structural aspect of silicon carbide powders preparing from nature silica sands of south Libya

The silicon carbide (SiC) powders were prepared from four types of silica sands taken as a silica source. These sand samples were collected from Alhasawneh Mountain, Murzuq city, Sebha city and Zalaf region located in the southern of Libya. Here, the carbon source was citrus sinensis tree branches and the sol-gel method was used for preparing the samples. The calcination process was performed by immersing SiC samples in a bath containing silica/carbon mixture (∼600 °C) for 6 h. The X-ray diffraction (XRD) results confirmed the formation of three polytypes of 6H, 3C and 21R–SiC. The cell parameter values of SiC samples were very close to the actual value. Excluding in the 21R phase, a slight increasing in the cell parameter c value of 53.08, 53.49, 53.82, 53.30 Å was observed for SiCAlhasawneh Mountain, SiCMurzuq sand, SiCSebha Sand and SiCZalaf sand samples, respectively. The particle morphology was measured using a field emission scanning electron microscopy (FE- SEM). The SiCAlhasawneh Mountain sample showed larger particles sizes with irregular shapes. The irregular particle with large holes (from 0.5 to few microns) was observed in the SiCMurzuq sand sample. The SiCSebha Sand sample contains a few hexagonal flakes ∼179 nm in diameter. The SiCZalaf sand sample showed irregular particles with an average size of 138 nm. Raman spectra of all samples showed D and G bands at 1360 cm−1 and 1600 cm−1, respectively. The weak peak at 798 cm−1 corresponded to the transverse optical (TO) mode that appeared in SiCZalaf sand sample. The results showed that it is possible to use natural silica sands and silica/carbon bath method for synthesis of SiC product with low cost and inexpensive materials to be used in many applications of industrials.

The Effect of Irrigation Rate on the Water Relations of Young Citrus Trees in High-Density Planting

The availability and proper irrigation scheduling of water are some of the most significant limitations on citrus production in Florida. The proper volume of citrus water demand is vital in evaluating sustainable irrigation approaches. The current study aims to determine the amount of irrigation required to grow citrus trees at higher planting densities without detrimental impacts on trees’ water relation parameters. The study was conducted between November 2017 and September 2020 on young sweet orange (Citrus sinensis) trees budded on the ‘US-897’ (Cleopatra mandarin x Flying Dragon trifoliate orange) citrus rootstock transplanted in sandy soil at the Southwest Florida Research and Education Center (SWFREC) demonstration grove, near Immokalee, Florida. The experiment contained six planting densities, including 447, 598, and 745 trees per ha replicated four times, and 512, 717, and 897 trees per ha replicated six times. Each density treatment was irrigated at 62% or 100% during the first 15 months between 2017 and 2019 or one of the four irrigation rates (26.5, 40.5, 53, or 81%) based on the calculated crop water supplied (ETc) during the last 17 months of 2019–2020. Tree water relations, including soil moisture, stem water potential, and water supplied, were collected periodically. In addition, soil salinity was determined. During the first year (2018), a higher irrigation rate (100% ETc) represented higher soil water contents; however, the soil water content for the lower irrigation rate (62% ETc) did not represent biological stress. One emitter per tree regardless of planting density supported stem water potential (Ψstem) values between −0.80 and −0.79 MPa for lower and full irrigation rates, respectively. However, when treatments were adjusted from April 2019 through September 2020, the results substantially changed. The higher irrigation rate (81% ETc) represented higher soil water contents during the remainder of the study, the lower irrigation rate (26.5% ETc) represents biological stress as a result of stem water potential (Ψstem) values between −1.05 and −0.91 MPa for lower and higher irrigation rates, respectively. Besides this, increasing the irrigation rate from 26.5% to 81%ETc decreased the soil salinity by 33%. Although increasing the planting density from 717 to 897 trees per hectare reduced the water supplied on average by 37% when one irrigation emitter was used to irrigate two trees instead of one, applying an 81% ETc irrigation rate in citrus is more efficient and could be managed in commercial groves.

Chemical Constituents and Anti-Inflammatory Effect of Incense Smoke from Agarwood Determined by GC-MS

Agarwood is generally used to make incense sticks in China and Southeast Asia. It emits smoke with a pleasant odor when burned. There are few reports on the chemical components of smoke generated by burning or heating agarwood. The agarwoods were produced by the whole-tree agarwood-inducing technique (AWIT), agarwood induced by axe wounds (AAW), burning-chisel-drilling agarwood (BCDA), wood of Aquilaria sinensis trees (AS), respectively. Herein, we used GC-MS to analyze the chemical constituents of incense smoke generated from AWIT, AAW, BCDA, AS, and the extracts of sticks from agarwood produced by the whole-tree agarwood-inducing technique (EAWIT), and 484 compounds were identified. A total of 61 chemical constituents were shared among AWIT, AAW, and BCDA. The experimental data showed that aromatic compounds were the main chemical constituents in agarwood smoke and that some chromone derivatives could be cracked into low-molecular-weight aromatic compounds (LACs) at high temperature. Furthermore, agarwood incense smoke showed anti-inflammatory activities by inhibiting lipopolysaccharide- (LPS-) induced TNF-α and IL-1α release in RAW264.7 cells.

Evaluation of physical, anatomical, and biometric characteristics of Citrus sinensis trees in longitudinal and transverse axes of stem

Three healthy Citrus sinensis (orange) trees in Babol, Iran, were randomly selected and cut. Two discs of 5 cm thickness were prepared along the tree (breast height and crown). In the transverse direction, the test specimens were cut 2 × 2 cm to 3 cm from the pith to the bark sequentially and examined. The biometric and physical properties were measured, and microscopic sections of wood near the bark were studied using light microscopy according to the International Association of Wood Anatomists’ (IAWA) List. Anatomical examination of the C. sinensis wood showed that the species was a diffuse porous hardwood, with indistinct growth rings, simple perforation plates, alternate intervessel pits, and banded parenchyma. The basic density and oven-dry density increased from the pith towards the tree bark and from the bottom of the tree towards the crown. There was a significant difference in both the transverse and longitudinal directions of the C. sinensis tree in terms of fiber length, fiber lumen diameter, fiber diameter, and cell wall thickness. The mean fiber length, fiber diameter, fiber lumen diameter, and cell wall thickness were 0.76 mm, 23.64 µm, 9.23 µm, and 14.41 µm, respectively.

Using genetic markers to identify the origin of illegally traded agarwood-producing Aquilaria sinensis trees

Because of high market demand, agarwood-producing trees are frequently illegally traded in Asia and are usually priced high if they are cut from natural forests. In China, some of these traded Aquilaria sinensis trees are declared to be from natural population(s) and are said to produce agarwood “easily and fast”. To distinguish the origins and genetic differences of natural populations from cultivated ones, we used genetic markers, microsatellites and single nucleotide polymorphisms (SNP) to compare them to trees from both cultivated and known natural origin trees. Our microsatellite results revealed that the illegally traded trees were genetically close to cultivated trees, indicating that they were of cultivated origin. By separating SNPs into genic (in genic regions) and nongenic categories representing functional and non-functional SNPs, our results revealed that the genic SNP markers did not detect more genetic differences between the illegally traded A. sinensis trees and cultivated ones than the nongenic SNP markers did, indicating that they are not functionally discernable from the cultivated trees. Our study revealed that sources labelled as natural by poachers might not have natural origins, which is especially true for agarwood-producing species given their limited natural populations and their long and extensive cultivation history. Our results may reduce the public’s desire for natural agarwood from A. sinensis and other agarwood-producing species and benefit the legal agarwood trade.