Bark structure is coordinated with xylem hydraulic properties in branches of five Cupressaceae species.

The properties of bark and xylem contribute to tree growth and survival under drought and other types of stress conditions. However, little is known about the functional coordination of the xylem and bark despite the influence of selection on both structures in response to drought. To this end, we examined relationships between proportions of bark components (i.e. thicknesses of tissues outside the vascular cambium) and xylem transport properties in juvenile branches of five Cupressaceae species, focusing on transport efficiency and safety from hydraulic failure via drought-induced embolism. Both xylem efficiency and safety were correlated with multiple bark traits, suggesting that xylem transport and bark properties are coordinated. Specifically, xylem transport efficiency was greater in species with thicker secondary phloem, greater phloem-to-xylem thickness ratio and phloem-to-xylem cell number ratio. In contrast, species with thicker bark, living cortex and dead bark tissues were more resistant to embolism. Thicker phellem layers were associated with lower embolism resistance. Results of this study point to an important connection between xylem transport efficiency and phloem characteristics, which are shaped by the activity of vascular cambium. The link between bark and embolism resistance affirms the importance of both tissues to drought tolerance.

Microstructural and histochemical analysis of shoots and cones of Juniperus seravschanica (Cupressaceae).

Juniper species contain abundant compounds that are used in the medicine, cosmetic, and wood industry. Furthermore, these components protect the genus against herbivores, pathogens and detrimental abiotic conditions. Stains and specific reagents can be used individually or simultaneously to mark cell shape, arrangement and the material they are made from. Microchemical analyses using specific reagents and stains under light microscopy are helpful for the characterization of chemical compounds present in plant tissues. The autofluorescence of endogenous fluorophores is used to enable their localization in plant cells and tissues. This paper aims to investigate the cytochemical and histochemical traits of the shoots (leaves and stems) and female cones (berries) of Juniperus seravschanica. Light and florescent microscopy techniques were used to analyze the cytology and localization of different compounds for the first time. Microscopy-based histochemical analyses revealed various products in terms of composition and distribution among the shoots and female cones. These specific compounds contained lignin, tannins, polysaccharides, starch, phenolic compounds, chlorophyll, terpenoids, neutral lipids, and proteins. However, the anatomical position of each metabolite and its concentration was different among leaf, stem, and female cone. Phenolic cells of young cones were differentiated into sclereid cells during development. The density of phenolic cells, sclereid cells, and resin glans was higher in female cones than leaves and stems. The high levels of various components can be related to high resistance of the species against biotic and abiotic stresses, confirm its industrial, pharmaceutical and agricultural applications and is useful for identification of diagnostic taxonomic traits. RESEARCH HIGHLIGHTS: Microscopical and histochemical analyses showed various compounds in J. seravschanica The phenolic cells differentiated to sclereid cells during development High levels of idioblasts and various compounds show its high resistance and medicinal role.

Authentication of Platycladus Orientalis Leaves and Its Five Adulterants by Combination of Morphology and Microscopic Characteristics, TLC, and HPLC Analysis.

BACKGROUND: Platycladus orientalis leaves (POL), as the source of the traditional Chinese medicine (TCM) Platycladi Cacumen, has frequently been found to be misused with five adulterants including Chamaecyparis obtusa leaves (COL), Cupressus funebris leaves (CFL), Juniperus virginiana leaves (JVL), Sabina chinensis leaves (SCL), and Juniperus formosana leaves (JFL). OBJECTIVE: The purpose of this study was to distinguish POL (fresh leaves) from its five adulterants (fresh leaves). METHODS: The micromorphological features in terms of transection and microscopic characteristics of POL and adulterants were captured and compared using the an microscope. Both HPLC and TLC methods for the simultaneous determination of six bioactive flavonoids (myricitrin, isoquercitrin, quercitrin, amentoflavone, afzelin, and hinokiflavone) have been developed. RESULTS: There were significant differences in microscopic features of transverse section and powders. The TLC results suggested that the spots of myricitrin in POL were more obvious than those in the five adulterants. The contents of myricitrin and quercitrin, or the total content of flavonoids in POL, determined by HPLC, were significantly higher than those in the adulterants. CONCLUSION: POL was successfully distinguished from its five adulterants by the comparison of morphology, microscopic characteristics, and chemical profiles. HIGHLIGHTS: This research provides a comprehensive morphology, microscopic identification, TLC, and HPLC analysis for authenticating POL and its five adulterants.

Complete mitochondrial genome of Thuja sutchuenensis and its implications on evolutionary analysis of complex mitogenome architecture in Cupressaceae.

BACKGROUND: The complex physical structure and abundant repeat sequences make it difficult to assemble the mitogenomes of seed plants, especially gymnosperms. Only approximately 33 mitogenomes of gymnosperms have been reported. However, as the most widely distributed and the second largest family among gymnosperms, Cupressaceae has only six assembled mitogenomes, including five draft mitogenomes and one complete mitogenome, which has greatly hindered the understanding of mitogenome evolution within this large family, even gymnosperms. RESULTS: In this study, we assembled and validated the complete mitogenome of Thuja sutchuenensis, with a size of 2.4 Mb. Multiple sequence units constituted its complex structure, which can be reduced to three linear contigs and one small circular contig. The analysis of repeat sequences indicated that the numbers of simple sequence repeats increased during the evolutionary history of gymnosperms, and the mitogenome of Thuja sutchuenensis harboured abundant extra-long repeats (more than 5 kb). Additionally, the longest repeat sequence identified in these seven gymnosperms also came from the mitogenome of Thuja sutchuenensis, with a length of up to 47 kb. The analysis of colinear blocks and gene clusters both revealed that the orders of mitochondrial genes within gymnosperms was not conserved. The comparative analysis showed that only four tRNAs were shared by seven gymnosperms, namely, trnD-GUC, trnE-UUC, trnI-CAU and trnY-GUA. Furthermore, four genes have undergone potential positive selection in most gymnosperm species, namely, atp8, ccmB, mttB and sdh4. CONCLUSION: We successfully assembled the second complete mitogenome within Cupressaceae and verified that it consisted of multiple sequence units. Our study also indicated that abundant long repeats may contribute to the generation of the complex conformation of the mitogenome of Thuja sutchuenensis. The investigation of Thuja sutchuenensis's mitogenome in our study provides new insight into further understanding the complex mitogenome architecture within gymnosperms.

Anti-Amyloidogenic Effects of Metasequoia glyptostroboides Fruits and Its Active Constituents.

Alzheimer's disease (AD) is a serious neurodegenerative brain disease that interferes with daily life. The accumulation of beta-amyloid (Aß), along with oxidative stress-inducing neurocellular apoptosis, has been considered one of the causes of AD. Thus, the purpose of this study is to find natural products that can reduce Aß accumulation. The ethanol extract of Metasequoia glyptostroboides Hu & Cheng fruits (Cupressaceae) significantly reduced the aggregation of Aß into oligomers and fibrils determined by Thioflavin T (ThT) assay. The solvent-partitioned ethyl acetate layer was further separated based on the bioassay-guided isolation method combined with the ThT assay. As a result, five compounds were isolated and elucidated as taxoquinone (1), sugiol (2), suginal (3), sandaracopimarinol (4), and sandaracopimaradien-19-ol (5) by comparing NMR data with references. All the compounds significantly reduced the aggregation of Aß and enhanced the disaggregation of pre-formed Aß aggregates in a dose-dependent manner. Furthermore, the inhibition of Aß aggregation by the compounds protected PC12 cells from Aß aggregate-induced toxicity. Among the five compounds, sandaracopimarinol (4) and sandaracopimaradien-19-ol (5) were the most effective. These results suggest that M. glyptostroboides and isolated five compounds have a potential for further study to be developed as anti-AD agents.

Cupressus arizonica Greene: Phytochemical Profile and Cosmeceutical and Dermatological Properties of Its Leaf Extracts.

For many decades, natural resources have traditionally been employed in skin care. Here, we explored the phytochemical profile of the aqueous and ethanolic leaf extracts of Cupressus arizonica Greene and assessed their antioxidant, antiaging and antibacterial activities in vitro. Liquid chromatography-mass spectrometry (LC-MS/MS) analysis led to the tentative identification of 67 compounds consisting mainly of phenolic and fatty acids, diterpene acids, proanthocyanidins and flavonoid and biflavonoid glycosides. The aqueous extract demonstrated substantial in vitro antioxidant potential at FRAP and DPPH assays and inhibited the four target enzymes (collagenase, elastase, tyrosinase, and hyaluronidase) engaged in skin remodeling and aging with IC50 values close to those of the standard drugs. Moreover, the aqueous extract at 25 mg/mL suppressed biofilm formation by Pseudomonas aeruginosa, a bacterial pathogen causing common skin manifestations, and decreased its swarming and swimming motilities. In conclusion, C. arizonica leaves can be considered a promising candidate for potential application in skin aging.

Bioactive Dimeric Diterpenoids from Taiwania cryptomerioides (Hayata) and Their Biological Activities.

Taiwania cryptomerioides Hayata is an endangered relict plant belonging to Taxodiaceae, and it is also an endemic plant to China. The decay-resistant of Taiwania timber can provide highly quality wood for building and furniture. Plenty of regenerative of leaves of T. cryptomerioides also has been used as a resource for the discovery of new dimeric diterpenoids. In a search for structurally diverse dimeric diterpenoids and potent bioactive isolates, ten new heterodimeric diterpenoids, taiwaniadducts K-T (1-4, 6, 8-11, and 14), along with five known ones (5, 7, 12, 13, and 15), were isolated from the leaves of T. cryptomerioides. These new compounds were defined by comprehensive spectroscopic analyses, putative biosynthetic pathways, and the values of optical. Biologically, anti-multidrug resistance (MDR) activities of compounds were evaluated. Compounds 4 and 10 exerted a 9.18-fold potentiation effect on bortezmib (BTZ) susceptibility at a tested concentration (20 µM) better than the positive control verapamil. The research of the leaves of T. cryptomerioides not only added the new data to the structural diversity and activities of dimeric diterpenoids but also could provide support for the medical and industrial application of the leaves of this endangered relict plant.

Biological activities of organic extracts and specialized metabolites from different parts of Cryptomeria japonica (Cupressaceae) - A critical review.

Forest operations and wood industry generate large amounts of residues that are discarded in the field and cause environmental pollution. However, these biomass residues are still raw materials to obtain value-added products, such as essential oils, organic/aqueous extracts and resins that are among the great natural sources of bioactive metabolites. Thus, in recent years, the scientific community is giving special attention to their valorization. To date, different uses of biomass residues have been proposed, such as a source of renewable energy, fertilizers, animal feed and bioactive molecules. In this context, Cryptomeria japonica biomass residues (e.g., bark and its exudate, heartwood, sapwood, leaves, cones and roots) represent a source of diverse specialized metabolites (e.g., sesqui-, di-, tri- and sesquarterpenes, flavonoids, lignans and norlignans) with potential application in different fields, particularly in the agrochemical, food, cosmeceutical, pharmaceutical, phytomedicine and esthetic, due to their valuable multi-bioactivities determined over the last decades. Thus, this review provides an overview of the reported biological activities of organic extracts/fractions and their specialized metabolites obtained from different parts of C. japonica, in order to encourage the alternative uses of C. japonica wastes/byproducts, and implement a sustainable and circular bioeconomy.

Chemical composition of essential oil from female cones of Cupressus arizonica Greene.

The hydrodistilled volatile essential oils extracted from the female cones of Cupressus arizonica Greene that harvested in winter and spring seasons were analysed for their chemical composition by using gas chromatography-mass spectrometry (GC/MS). Twenty-four and seventeen components were identified, accounting for winter (95.5%) and spring (96.9%) of the total oils volume, respectively. Monoterpenoids (winter 93.7% and spring 95.0%) dominated the identified components in the essential oils, followed by a small portion of sesquiterpenoids (winter 1.8% and spring 1.9%). Monoterpene hydrocarbons (MH) (winter 90.9% and spring 94.9%) were the principal subclasses of components with α-pinene (winter 42% and spring 72%), ß-myrcene (winter 18.5% and spring 7.7%), δ-3-carene (winter 11.3% and spring 5.1%), limonene (9.4% for winter), and ß-pinene (5.3% for spring) as main constituents. Limonene (9.4%), camphor (0.2%), exo-methylcamphenilol (0.2%), terpinene-4-ol (0.6%), ß-citronellol (0.9%), and bornyl acetate (0.3%) were representative of the monoterpene hydrocarbon and oxygen-containing monoterpenoids (OM) in winter essential oil.

Carbon sequestration characteristics of two plantation forest ecosystems with different lithologies of karst.

In karst regions, the majority of studies have focused on ecosystem carbon sequestration in the same lithology, but no studies in different lithologies. In this study, actual measurements were used to reveal carbon sequestration characteristics of two plantation forest ecosystems (Bodinieri cinnamon and Cupressus funebris) with different lithologies of karst. The results showed that the tree layer showed the highest vegetation biomass, carbon content, carbon density, and ratio of aboveground biomass to belowground biomass. The carbon density of B. cinnamon plantation and C. funebris plantation was high in dolomite and in limestone respectively. The soil quality and carbon density of bare ground and plantation varied across different lithologies. The carbon density of various ecosystem components was in the order of vegetation>soil>litterfall. The carbon density and net carbon density of plantation varied across different lithologies. In B. cinnamon plantation, the carbon sequestration rate of vegetation and ecosystem was high in dolomite, moderate in limestone, and low in dolomitic sandstone. In Cupressus funebris plantation, the carbon sequestration rate was in the order of limestone>dolomite>dolomitic sandstone. These findings revealed that lithology is an important factor affecting ecosystem carbon pools, and plantation ecosystems have low biomass and low carbon density in karst areas.

Miocene Cupressinoxylon from Gökçeada (Imbros), Turkey with Protophytobia cambium mining and the study of ecological signals of wood anatomy.

Premise: The recognition of the Miocene Climate Optimum (MCO) in terrestrial palaeoenvironments of the Eastern Mediterranean is restricted to Lesbos and Lemnos Islands, Greece. This area is significant for its wood microfossils. A recently-discovered fossil wood assemblage from Gökçeada (Imbros) Island, Turkey, including tree species similar to the Greek findings, is thought to have an early Miocene age. Here, we revise the age of the latter plant fossiliferous locality, re-evaluate the area for the study of MCO for the terrestrial palaeoecosystems of the Eastern Mediterranean and the nomenclature errors referring to the occurrence of fossil wood. We present the plant-insect-environment interactions using detailed anatomical descriptions, of an extinct conifer and its extinct cambium miner feeding traces observed in its secondary xylem. Methods: Three thin sections were prepared with standard palaeoxylotomical techniques from a small section of the silicified wood; the sections were observed under a light microscope. The anatomy of the conifer and its damage patterns were compared with those of extant and fossil Cupressaceae and Agromyzidae, respectively. Pivotal results: The common anatomical features of the studied wood specimen and Hesperocyparis macrocarpa (Hartw.) Bartel and a shared characteristic (the number of the cross-field pits - a feature we consider of diagnostic value) with Xanthocyparis vietnamensis Farjon & T.H. Nguyên led to its assignment to the Hesperocyparis-Xanthocyparis-Callitropsis clade. The detailed study of the wound scars and anatomical abnormalities, the anatomical-environmental associations, and structural-functional reactions follow the identification of the wood's anatomy sensu Carlquist providing decisive results. Conclusions: Based on the distinctive characteristics presented, we identify our macrofossil as Cupressinoxylon matromnense Grambast, a stem or an extinct lineage of the Hesperocyparis-Xanthocyparis vietnamensis-Callitropsis nootkatensis clade with feeding traces of the fossil cambium miner of the genus Protophytobia Süss (Diptera: Agromyzidae), and anatomical damage and reaction tissue on adventitious shoots. The use of Protopinaceae and Pinoxylon F. H. Knowlton from the eastern Mediterranean are re-evaluated and corrections are provided. The age of the studied plant fossiliferous locality in Gökçeada is revised as middle Miocene, allowing the proposal of an eastern Mediterranean MCO hotspot, including Lesbos, Lemnos, and Gökçeada (Imbros) Islands.

Chemical Constituents of the Leaves of Thujopsis dolabrata and Their Cytotoxicity.

Five podophyllotoxin derivatives (1-5), two diterpenoids (6 and 7), three diterpenoid xylosides (8-10), a flavanonol glycoside (11), flavonol (12), and biflavonoid (13) were isolated from the leaves of Thujopsis dolabrata (Cupressaceae). Compounds 1, 6, and 8 were named (-)-ß-isopeltatin, epi-nootkastatin 2, and acetoxyanticopalol 15-O-ß-D-xylopyranoside, respectively. The structures of the isolated compounds were determined based on a detailed analysis of NMR spectroscopic data and through chromatographic and spectroscopic analyses following specific chemical transformations. The isolated compounds (1-5 and 7-11) were evaluated for their cytotoxicity toward HL-60 human promyelocytic leukemia cells and Caki-1 human kidney carcinoma cells. The podophyllotoxin derivatives (1-5) exhibited cytotoxicity against both HL-60 and Caki-1 cells with IC50 values ranging from 0.00069 to 5.4 µM, and the diterpenoid derivatives (7-10) demonstrated cytotoxicity against HL-60 cells with IC50 values ranging from 4.5 to 11 µM. HL-60 cells treated with 8 exhibited apoptosis characteristics, such as accumulation of sub-G1 cells and nuclear chromatin condensation.

Phylogeny and evolution of Cupressaceae: Updates on intergeneric relationships and new insights on ancient intergeneric hybridization.

After the merger of the former Taxodiaceae and Cupressaceae s.s., currently the conifer family Cupressaceae (sensu lato) comprises seven subfamilies and 32 genera, most of which are important components of temperate and mountainous forests. With the exception of a recently published genus-level phylogeny of gymnosperms inferred from sequence analysis of 790 orthologs, previous phylogenetic studies of Cupressaceae were based mainly on morphological characters or a few molecular markers, and did not completely resolve the intergeneric relationships. In this study, we reconstructed a robust and well-resolved phylogeny of Cupressaceae represented by all 32 genera, using 1944 genes (Orthogroups) generated from transcriptome sequencing. Reticulate evolution analyses detected a possible ancient hybridization that occurred between ancestors of two subclades of Cupressoideae, including Microbiota-Platycladus-Tetraclinis (MPT) and Juniperus-Cupressus-Hesperocyparis-Callitropsis-Xanthocyparis (JCHCX), although both concatenation and coalescent trees are highly supported. Moreover, divergence time estimation and ancestral area reconstruction indicate that Cupressaceae very likely originated in Asia in the Triassic, and geographic isolation caused by continental separation drove the vicariant evolution of the two subfamilies Cupressoideae and Callitroideae in the northern and southern hemispheres, respectively. Evolutionary analyses of some morphological characters suggest that helically arranged linear-acicular leaves and imbricate bract-scale complexes represent ancestral states, and the shift from linear-acicular leaves to scale-like leaves was associated with the shift from helical to decussate arrangement. Our study sheds new light on phylogeny and evolutionary history of Cupressaceae, and strongly suggests that both dichotomous phylogenetic and reticulate evolution analyses be conducted in phylogenomic studies.

Anti-mosquito properties of Pelargonium roseum (Geraniaceae) and Juniperus virginiana (Cupressaceae) essential oils against dominant malaria vectors in Africa.

BACKGROUND: More than 90% of malaria cases occur in Africa where the disease is transmitted by Anopheles gambiae and Anopheles arabiensis. This study evaluated the anti-mosquito properties of Juniperus virginiana (JVO) and Pelargonium roseum (PRO) essential oils (EOs) against larvae and adults of An. gambiae sensu lato (s.l.) from East Africa in laboratory and semi-field conditions. METHODS: EOs was extracted from the aerial green parts of Asian herbs by hydrodistillation. Their constituents were characterized by gas chromatography-mass spectrometry (GC-MS). Larvicidal activities of JVO, PRO, and PRO components [citronellol (CO), linalool (LO), and geraniol (GO)] were investigated against An. gambiae sensu stricto (s.s.). The percentage of knockdown effects and mortality rates of all oils were also evaluated in the adults of susceptible An. gambiae s.s. and permethrin-resistant An. arabiensis. RESULTS: GC-MS analyses identified major constituents of JVO (sabinene, dl-limonene, ß-myrcene, bornyl acetate, and terpinen-4-ol) and PRO (citronellol, citronellyl formate, L-menthone, linalool, and geraniol). Oils showed higher larvicidal activity in the laboratory than semi-field trials. The LC50 values for JVO/PRO were computed as 10.82-2.89/7.13-0.9 ppm and 10.75-9.06/13.63-8.98 ppm in laboratory and semi-field environments, respectively at exposure time of 24-72 h. The percentage of knockdown effects of the oils were also greater in An. gambiae s.s. than in An. arabiensis. Filter papers impregnated with JVO (100 ppm) and PRO (25 ppm) displayed 100% mortality rates for An. gambiae s.s. and 3.75% and 90% mortality rates, for An. arabiensis populations, respectively. Each component of CO, LO, and GO exhibited 98.13%, 97.81%, and 87.5%, respectively, and a mixture of the PRO components indicated 94.69% adult mortality to permethrin-resistant An. arabiensis. CONCLUSIONS: The findings of this study show that PRO and its main constituents, compared to JVO, have higher anti-mosquito properties in terms of larvicidal, knockdown, and mortality when applied against susceptible laboratory and resistant wild populations of An. gambiae s.l. Consequently, these oils have the potential for the development of new, efficient, safe, and affordable agents for mosquito control.

Comparative analyses of six complete chloroplast genomes from the genus Cupressus and Juniperus (Cupressaceae).

Cupressaceae is a conifer family distributed around the world. Cupressus and Juniperus are the main genera of the Cupressaceae family and have important medicinal value. This leads to confusion between Cupressus and Juniperus due to similar morphologies. Here, the complete cp genomes of two Cupressus (C. duclouxiana and C. funebri) and four Juniperus (J. chinensis, J. gaussenii J. pingii and J. procumbens) were sequenced. The results revealed that the length of the cp genomes ranged from 126,996 bp to 129,959 bp, with 119 genes comprising 82 protein-coding genes, 33 transfer RNAs and 4 ribosomal RNAs. All chloroplast genomes of Cupressus and Juniperus lost whole IR regions, which is consistent with gymnosperm cp genome studies. In addition, the number of SSRs per species ranged from 54 to 73 and was dominated by mononucleotide repeats. In the six cp genomes of Cupressus and Juniperus, five highly divergent regions, including accD, accD-rpl2, ycf1, ycf2 and rrn23-rrn4.5, can be used as DNA barcodes of interspecific relationships and potential genetic markers. We compared the gene selection pressures (C. chengiana as reference species), and 6 genes underwent positive selection, the majority of which were related to photosynthesis. Phylogenetic results showed that the monophyly of Cupressus and Juniperus supported most bootstrap support. Cupressus funebris and J. chinensis were resolved to be early diverging species within Cupressus and Juniperus, and the two genera were sister groups to each other. This research revealed a new understanding of the structural pluralism and phylogenetic relationships of Cupressaceae cp genomes. These results will facilitate comprehension of the complexity and diversity of conifer cp genomes.

Incomplete lineage sorting and local extinction shaped the complex evolutionary history of the Paleogene relict conifer genus, Chamaecyparis (Cupressaceae).

Inferring accurate biogeographic history of plant taxa with an East Asia (EA)-North America (NA) is usually hindered by conflicting phylogenies and a poor fossil record. The current distribution of Chamaecyparis (false cypress; Cupressaceae) with four species in EA, and one each in western and eastern NA, and its relatively rich fossil record, make it an excellent model for studying the EA-NA disjunction. Here we reconstruct phylogenomic relationships within Chamaecyparis using > 1400 homologous nuclear and 61 plastid genes. Our phylogenomic analyses using concatenated and coalescent approaches revealed strong cytonuclear discordance and conflicting topologies between nuclear gene trees. Incomplete lineage sorting (ILS) and hybridization are possible explanations of conflict; however, our coalescent analyses and simulations suggest that ILS is the major contributor to the observed phylogenetic discrepancies. Based on a well-resolved species tree and four fossil calibrations, the crown lineage of Chamaecyparis is estimated to have originated in the upper Cretaceous, followed by diversification events in the early and middle Paleogene. Ancestral area reconstructions suggest that Chamaecyparis had an ancestral range spanning both EA and NA. Fossil records further indicate that this genus is a relict of the "boreotropical" flora, and that local extinctions of European species were caused by global cooling. Overall, our results unravel a complex evolutionary history of a Paleogene relict conifer genus, which may have involved ILS, hybridization and the extinction of local species.

Persistence of airborne tree pollen from the Cupressaceae family during the last decade in the city of Bahia Blanca.

Airborne pollen is a major contributor to allergic respiratory diseases. However, the literature on patterns and seasonality of specific pollen types mainly comes from northern hemisphere and developed regions, limiting our ability to extrapolate these findings to other geographical locations. With this research letter, our aim is to contribute to the current knowledge of aerobiology by analyzing the decade-long patterns of airborne tree pollen in the city of Bahia Blanca, Argentina. In general, we found late winter to early spring as the period with the highest Cupressaceae pollen counts. In 2020, the average pollen count during July through September was 78.81 (SD 79.70), the highest recorded during the last 10 years. These months had varying pollen concentrations from moderate (15-89 grains/m3 of air) to high (90-1499 grains/m3 of air). Regardless of such variation, August had consistently been the month with the highest peak concentrations from 2010 to 2020 (61.2, SD 57.3), followed by September (27.1, SD 20.3). We did not find any month with very high (˃1500 grains/m3 of air) peak concentration. Further studies need to be done to expand our knowledge on aerobiology to characterize specific pollen sub-types and determine the exact allergenic potential of airborne pollen in different regions.

Persistence of airborne tree pollen from the Cupressaceae family during the last decade in the city of Bahia Blanca

Airborne pollen is a major contributor to allergic respiratory diseases. However, the literature on patterns and seasonality of specific pollen types mainly comes from northern hemisphere and developed regions, limiting our ability to extrapolate these findings to other geographical locations. With this research letter, our aim is to contribute to the current knowledge of aerobiology by analyzing the decade-long patterns of airborne tree pollen in the city of Bahia Blanca, Argentina. In general, we found late winter to early spring as the period with the highest Cupressaceae pollen counts. In 2020, the average pollen count during July through September was 78.81 (SD 79.70), the highest recorded during the last 10 years. These months had varying pollen concentrations from moderate (15–89 grains/m3 of air) to high (90–1499 grains/m3 of air). Regardless of such variation, August had consistently been the month with the highest peak concentrations from 2010 to 2020 (61.2, SD 57.3), followed by September (27.1, SD 20.3). We did not find any month with very high (˃1500 grains/m3 of air) peak concentration. Further studies need to be done to expand our knowledge on aerobiology to characterize specific pollen sub-types and determine the exact allergenic potential of airborne pollen in different regions (AU)