How tree species have modified the potentially toxic elements distributed in the developed soil-plant system in a post-fire site in highly industrialized region.

The biogeochemical cycles of trace elements are changed by fire as a result of the mineralization of organic matter. Monitoring the accumulation of trace elements in both the environment and the tree biomass during the post-fire (PF) forest ecosystem regeneration process is important for tree species selection for reforestation in ecosystems under anthropogenic pressure. We analyzed the soil concentrations of different groups of potentially toxic elements (PTEs), including beneficial (Al), toxic (Cd, Cr, Pb), and microelements (Cu, Mn, Ni, Zn), and their bioaccumulation in the tree species (Pinus sylvestris, Betula pendula, Alnus glutinosa) biomass introduced after a fire in a forest weakened by long-term emissions of industrial pollutants. The results indicated no direct threat from the PTEs tested at the PF site. The tree species introduced 30 years ago may have modified the biogeochemical cycles of the PTEs through different strategies of bioaccumulation in the belowground and aboveground biomass. Alder had relatively high Al concentrations in the roots and a low translocation factor (TF). Pine and birch had lower Al concentrations in the roots and higher TFs. Foliage concentrations and the TF of Cd increased from alder to pine to birch. However, the highest concentration and bioaccumulation factor of Cd was found in the alder roots. The concentrations of Cr in the foliage and the Cr TFs in the studied species increased from pine to birch to alder. Higher concentrations of Cu and Ni were found in the foliage of birch and alder than of pine. Among the species, birch also had the highest Pb and Zn concentrations in the roots and foliage. We found that different tree species had different patterns of PTE phytostabilization and ways they incorporated these elements into the biological cycle, and these patterns were not dependent on fire disturbance. This suggests that similar patterns might also occur in more polluted soils. Therefore, species-dependent bioaccumulation patterns could also be used to design phytostabilization and remediation treatments for polluted sites under industrial pressure.

Discovery of a new bacterium, Microbacterium betulae sp. nov., in birch wood associated with hypersensitivity pneumonitis in woodworkers.

A Gram-positive, aerobic, rod-shaped mesophilic bacterium was isolated from birch wood, referred to as the AB strain. Allergological tests suggest that this strain may cause allergic alveolitis in sawmill workers. Employing a polyphasic taxonomic approach, the AB strain's 16S rRNA gene sequence showed high similarity to Microbacterium barkeri and M. oryzae, with 97.25% and 96.91%, respectively, a finding supported by rpoB and gyrB sequence analysis. Further genome sequence comparison with the closely related M. barkeri type strain indicated a digital DNA-DNA hybridization value of 25.5% and an average nucleotide identity of 82.52%. The AB strain's cell wall peptidoglycan contains ornithine, and its polar lipids comprise diphosphatidylglycerol, phosphatidylglycerol, and unidentified glycolipids. Its major fatty acids include anteiso C15:0, anteiso C17:0, and iso C16:0, while MK-10 is its predominant respiratory quinone. Comprehensive analysis through 16S rRNA, whole-genome sequencing, phenotyping, chemotaxonomy, and MALDI-TOF MS profiling indicates that the AB strain represents a new species within the Microbacterium genus. It has been proposed to name this species Microbacterium betulae sp. nov., with ABT (PCM 3040T = CEST 30706T) designated as the type strain.

Carbon quantum dots from carbohydrate-rich residue of birch obtained following lignin-first strategy.

Carbon quantum dots (CQDs) were successfully synthesized from carbohydrate-rich residue of birch obtained following the lignin-first strategy. The optical and physicochemical properties of the CQDs were studied, along with their potential for photocatalytic pollutant degradation. By combining solvothermal and chemical oxidation methods, the product yield of CQDs from carbohydrate-rich residue reached 8.1 wt%. Doping nitrogen enhances the graphitization of CQDs and introduces abundant amino groups to the surface, thereby boosted the quantum yield significantly from 8.9 % to 18.7 %-19.3 %. Nitrogen-doped CQDs exhibited efficient photocatalytic degradation of methylene blue, reaching 37 % within 60 min, with a kinetic degradation rate of 0.00725 min-1. This study demonstrates that carbohydrate-rich residue obtained from lignin-first strategy are ideal precursors for synthesizing CQD with high mass yield and quantum yield by combining solvothermal treatment and chemical oxidation methods, offering a novel approach for the utilization of whole biomass components following the lignin-first strategy.

Effects of industrial pollution and ambient air temperature on larval performance and population dynamics of Eriocrania leafminers (Lepidoptera).

Pollution is an integral part of global environmental change, yet the combined and interactive effects of pollution and climate on terrestrial ecosystems remain inadequately understood. This study aims to explore whether pollution alters the impacts of ambient air temperature on the population dynamics of herbivorous insects. Between 1995 and 2005, we studied populations of two closely related moths, Eriocrania semipurpurella and E. sangii, at eight sites located 1 to 64 km from a large copper­nickel smelter in Monchegorsk, Russia. We found that pollution and temperature influence the performance of Eriocrania larvae mining in the leaves of mountain birch, Betula pubescens var. pumila, through multiple pathways. This is evident from the unconsistent changes observed in larval and frass weight, mine area, and leaf size. We found increases in both leaf quality and larval weight with decreasing pollution levels at both spatial and temporal scales and attributed these to the impact of sulphur dioxide, rather than trace elements (nickel and copper). The quality of birch leaves increased with spring (May) temperatures, enabling Eriocrania larvae to achieve greater weight while consuming less biomass. During the larval growth period (early June to early July), Eriocrania larvae increased their consumption with rising temperatures, presumably to compensate for increased metabolic expenses. Contrary to our expectations, the per capita rate of population change did not correlate with larval weight and did not vary along the pollution gradient. Nevertheless, we detected interactive effects of pollution and climate on the rate of population change. This rate decreased with rising winter temperatures in slightly polluted and unpolluted sites but remained unchanged in heavily polluted sites. We conclude that pollution disrupts mechanisms regulating the natural population dynamics of Eriocrania moths.

Cryptic diploid lineage of Betula ermanii at its southern boundary populations in Japan.

Polyploidy is thought to enable species diversification and adaptation to extreme environments. Resolving the ecological differences between a taxon's ploidy levels would therefore provide important insights into local adaptation and speciation. The genus Betula includes many polyploids, but estimates of their phylogenetic relationships and evolutionary history are uncertain because of cryptic lineages and species. As one of the southern boundary populations of Betula ermanii in Japan has been shown to have distinctive genetic characteristics and traits, the differences in ploidy levels between three southern boundary and various other Japanese B. ermanii populations were investigated using flow cytometry. Leaf and seed morphologies were also compared. Apart from individuals in southern boundary populations, all those sampled were tetraploid. Individuals from the southern boundary populations were mostly diploid, apart from a few from lower altitude Shikoku populations, which were tetraploid. Leaf and seed morphologies differed between tetraploids and diploids. Diploid individuals were characterized by leaves with a heart-shaped base and many leaf teeth, and seeds with relatively longer wings. The diploid populations could be considered a cryptic relict lineage of B. ermanii, and there is a possibility that this lineage is a diploid ancestor of B. ermanii and a relict population of the Sohayaki element. Further investigation of the Japanese Betula phylogenetic relationships would enable an informed discussion of taxonomic revisions.

Modulation of Bronchial Epithelial Barrier Integrity by Low Molecular Weight Components from Birch Pollen.

Pollen, in addition to allergens, comprise low molecular weight components (LMC) smaller than 3 kDa. Emerging evidence indicates the relevance of LMC in allergic immune responses. However, the interaction of birch pollen (BP)-derived LMC and epithelial cells has not been extensively studied. We investigated epithelial barrier modifications induced by exposure to BP LMC, using the human bronchial epithelial cell line 16HBE14o-. Epithelial cell monolayers were apically exposed to the major BP allergen Bet v 1, aqueous BP extract or BP-derived LMC. Barrier integrity after the treatments was monitored by measuring transepithelial electrical resistance at regular intervals and by using the xCELLigence Real-Time Cell Analysis system. The polarized release of cytokines 24 h following treatment was measured using a multiplex immunoassay. Epithelial barrier integrity was significantly enhanced upon exposure to BP LMC. Moreover, BP LMC induced the repair of papain-mediated epithelial barrier damage. The apical release of CCL5 and TNF-α was significantly reduced after exposure to BP LMC, while the basolateral release of IL-6 significantly increased. In conclusion, the results of our study demonstrate that BP-derived LMC modify the physical and immunological properties of bronchial epithelial cells and thus regulate airway epithelial barrier responses.

A putative Na+/H+ antiporter BpSOS1 contributes to salt tolerance in birch.

White birch (Betula platyphylla Suk.) is an important pioneer tree which plays a critical role in maintaining ecosystem stability and forest regeneration. The growth of birch is dramatically inhibited by salt stress, especially the root inhibition. Salt Overly Sensitive 1 (SOS1) is the only extensively characterized Na+ efflux transporter in multiple plant species. The salt-hypersensitive mutant, sos1, display significant inhibition of root growth by NaCl. However, the role of SOS1 in birch responses to salt stress remains unclear. Here, we characterized a putative Na+/H+ antiporter BpSOS1 in birch and generated the loss-of-function mutants of the birch BpSOS1 by CRISPR/Cas9 approach. The bpsos1 mutant exhibit exceptional increased salt sensitivity which links to excessive Na+ accumulation in root, stem and old leaves. We observed a dramatic reduction of K+ contents in leaves of the bpsos1 mutant plants under salt stress. Furthermore, the Na+/K+ ratio of roots and leaves is significant higher in the bpsos1 mutants than the wild-type plants under salt stress. The ability of Na+ efflux in the root meristem zone is found to be impaired which might result the imbalance of Na+ and K+ in the bpsos1 mutants. Our findings indicate that the Na+/H+ exchanger BpSOS1 plays a critical role in birch salt tolerance by maintaining Na+ homeostasis and provide evidence for molecular breeding to improve salt tolerance in birch and other trees.

Accumulation ability of trace metals by silver birch leaves in areas contaminated by Zn-Pb ore processing: Effects of excessive trace metal accumulation on specialized metabolism.

The study was carried out in the most industrialised region of southern Poland. Four areas were selected for the study: the vicinity of the Miasteczko Slaskie Zn-Pb-works (ZW; with three transects selected: A, B, and C), and the metalliferous waste heaps (H1, H2, H3). Samples were taken from the surface soil layer, while only mature silver birch (Betula pendula Roth) trees (3-4 m high) growing spontaneously in the study area were selected for the collection of leaves. The analysis of metals including trace metals (TMs; Ag, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Ni, Pb, Tl, and Zn) in the soil and leaves, as well as the contents of specialized leaf compounds belonging to polyphenols were performed. In general, the B. pendula trees in transects A and B located within 500 m of the furnaces exhibited 3-9 times higher content of TMs in their leaves compared to the plants located further away from the Zn smelter. In contrast, the quantity of TM in trees from transect C was independent of distance. The accumulation of TMs in the leaves was significantly lower in the metalliferous waste heap sites compared to the ZW area. It was hypothesised that the accumulation of TMs in B. pendula leaves would depend on the location and distance from the polluting source. It was demonstrated that TMs content in soil affects the accumulation of phenolic acids and flavonoids.

Flavonols do not affect aphid load in green or senescing birch leaves but coincide with a decrease in Photosystem II functionality.

Instead of red anthocyanins, birches synthesise colourless (to human eye), UV-absorbing flavonols during autumn senescence. To test if flavonols protect against insects, and if leaves with high or low amounts of flavonols differ in their photosynthetic functions, aphid-free and aphid-infested green and senescing birch leaves were collected from outdoor-grown trees and analysed. Photosynthetic parameters were greatly affected by the leaf chlorophyll content (i.e. the phase of senescence). Photochemical quenching and the amount of functional Photosystem I decreased linearly with chlorophyll content, while FV/FM (Photosystem II functionality) decreased strongly only at the end of senescence. Non-photochemical quenching of excitation energy (NPQ) increased towards the end of senescence. However, no significant differences in the total flavonol amounts, nor in individual flavonol species, were found between aphid-free and aphid-infested leaves, suggesting that flavonols play no role in defence against aphid herbivory. Interestingly, both green and senescing leaves with a high flavonol content showed low FV/FM values. High flavonol content slowed down PSII photoinhibition and improved recovery, but only in green leaves. Previously, we proposed that anthocyanins provide an additional sink for photosynthates at the nitrogen resorption phase during autumn senescence, and the present data may suggest that flavonol synthesis plays a similar role.

Seasonal dynamics and punctuated carbon sink reduction suggest photosynthetic capacity of boreal silver birch is reduced by the accumulation of hexose.

The 'assimilates inhibition hypothesis' posits that accumulation of nonstructural carbohydrates (NSCs) in leaves reduces leaf net photosynthetic rate, thus internally regulating photosynthesis. Experimental work provides equivocal support mostly under controlled conditions without identifying a particular NSC as involved in the regulation. We combined 3-yr in situ leaf gas exchange observations (natural dynamics) in the upper crown of mature Betula pendula simultaneously with measurements of concentrations of sucrose, hexoses (glucose and fructose), and starch, and similar measurements during several one-day shoot girdling (perturbation dynamics). Leaf water potential and water and nitrogen content were measured to account for their possible contribution to photosynthesis regulation. Leaf photosynthetic capacity (A/Ci) was temporally negatively correlated with NSC accumulation under both natural and perturbation states. For developed leaves, leaf hexose concentration explained A/Ci variation better than environmental variables (temperature history and daylength); the opposite was observed for developing leaves. The weaker correlations between NSCs and A/Ci in developing leaves may reflect their strong internal sink strength for carbohydrates. By contrast, the strong decline in photosynthetic capacity with NSCs accumulation in mature leaves, observed most clearly with hexose, and even more tightly with its constituents, provides support for the role of assimilates in regulating photosynthesis under natural conditions.

NLRP3 promotes allergic responses to birch pollen extract in a model of intranasal sensitization.

Introduction & Objective: Allergic sensitization is an essential step in the development of allergic airway inflammation to birch pollen (BP); however, this process remains to be fully elucidated. Recent scientific advances have highlighted the importance of the allergen context. In this regard, microbial patterns (PAMPs) present on BP have attracted increasing interest. As these PAMPs are recognized by specialized pattern recognition receptors (PRRs), this study aims at investigating the roles of intracellular PRRs and the inflammasome regulator NLRP3. Methods: We established a physiologically relevant intranasal and adjuvant-free sensitization procedure to study BP-induced systemic and local lung inflammation. Results: Strikingly, BP-sensitized Nlrp3-deficient mice showed significantly lower IgE levels, Th2-associated cytokines, cell infiltration into the lung, mucin production and epithelial thickening than their wild-type counterparts, which appears to be independent of inflammasome formation. Intriguingly, bone-marrow chimera revealed that expression of NLRP3 in the hematopoietic system is required to trigger an allergic response. Conclusion: Overall, this study identifies NLRP3 as an important driver of BP-induced allergic immune responses.

[Application of micro-computed tomography (µCT)in quantifying xylem vessels of broadleaved trees]. / 计算机显微断层扫描技术(µCT)åœ¨é‡åŒ–é˜”å¶æ ‘ç§å¯¼ç®¡ä¸­çš„åº”ç”¨.

Quantitative analysis of vessel characteristics at the cellular scale is of great significance for understan-ding plant adaptation strategies to environment. The direct grinding combined with stereo-microscope imaging is one of the main approaches to examine the anatomical structure of xylem (conifer tracheid and hardwood vessel) wood structure, which inevitably damages xylem cells, hindering the accurate understanding of anatomical structures. In this study, we applied X-ray micro-computed tomography (µCT) and stereo-microscope technology to quantitatively measure the diameter and area of vessels of seven Canadian broadleaved tree species (Acer saccharum, Betula papyrifera, Fraxinus americana, Ostrya virginiana, Populus grandidentata, Quercus rubra, and Carya cordiformis). We fitted the results by linear model and tested the feasibility of µCT technology in quantifying the vessel size of broadleaved species. We found that the results of the two methods for measuring vessel size were highly similar (R2=0.98). The goodness of fit of the vessel diameter results measured by the two methods for the ring-porous wood species (C. cordiformis, R2=0.98; F. americana, R2=0.96; Q. rubra, R2=0.99) was higher than that of the diffuse-porous wood species (B. papyrifera, R2=0.88; O. virginiana, R2=0.73; A. saccharum, R2=0.68; P. grandiden-tata, R2=0.88). The goodness of fit of small vessels (diameter≤200 µm, R2=0.94) measured by the two methods was higher than that of large vessels (diameter>200 µm, R2=0.92). Thus, the µCT technique provided a new non-destructive detection method for quantifying xylem vessels of broadleaved tree species.

Molecular characterization of birch toti-like virus, a plant-associated member of the new family Orthototiviridae.

A novel totivirus, named "birch toti-like virus" (BTLV), was discovered in European white birch (Betula pendula) plants. The genome of BTLV is 4,967 nucleotides long and contains two overlapping open reading frames (ORFs) coding for the capsid protein (CP) and an RNA-dependent RNA-polymerase (RdRP). The encoded CP and RdRP proteins shared 46.9% and 60.2% amino acid sequence identity, respectively, with those of Panax notoginseng virus B. The presence of a putative slippery heptamer signal 82 nt upstream of the stop codon of ORF1 suggests that a -1 translational frameshifting strategy is involved in the expression of ORF2, like in other totiviruses. Phylogenetic analysis based on the CP and RdRP amino acid sequences placed this virus within a clade of plant-associated totiviruses, with taro-associated virus as its closest relative. Hence, based on its distinct host and the amino acid sequence similarity between BTLV and its relatives, we conclude that birch toti-like virus is a new member of the genus Totivirus.

Balance between carbon gain and loss in warmer environments: impacts on photosynthesis and leaf respiration in four temperate tree species.

The temperature sensitivities of photosynthesis and respiration remain a key uncertainty in predicting how forests will respond to climate warming. We grew seedlings of four temperate tree species, including Betula platyphylla, Fraxinus mandshurica, Juglans mandshurica and Tilia amurensis, at three temperature regimes (ambient, +2 °C, and +4 °C in daytime air temperature). We investigated net photosynthesis (Anet25), maximum rate of RuBP-carboxylation (Vcmax25) and RuBP-regeneration (Jmax25), stomatal conductance (gs25), mesophyll conductance (gm25), and leaf respiration (Rleaf) in dark (Rdark25) and in light (Rlight25) at 25 °C in all species. Additionally, we examined the temperature sensitivities of Anet, Vcmax, Jmax, Rdark and Rlight in F. mandshurica. Our findings showed that the warming-induced decreases in Anet25, Vcmax25 and Jmax25 were more prevalent in the late-successional species T. amurensis. Warming had negative impacts on gs25 in all species. Overall, Anet25 was positively correlated with Vcmax25 and Jmax25 across all growth temperatures. However, a positive correlation between Anet25 and gs25 was observed only under warming conditions, and gs25 was negatively associated with vapor pressure deficit. This implies that the vapor pressure deficit-induced decrease in gs25 was responsible for the decline in Anet25 at higher temperatures. The optimum temperature of Anet in F. mandshurica increased by 0.59 °C per 1.0 °C rise in growth temperature. While +2 °C elevated the thermal optima of Jmax, it did not affect the other temperature sensitivity parameters of Vcmax and Jmax. Rdark25 was not affected by warming in any species, and Rlight25 was stimulated in T. amurensis. The temperature response curves of Rdark and Rlight in F. mandshurica were not altered by warming, implying a lack of thermal acclimation. The ratios of Rdark25 and Rlight25 to Anet25 and Vcmax25 in T. amurensis increased with warming. These results suggest that Anet and Rleaf did not acclimate to warming synchronously in these temperate tree species.

Birch pollen-induced signatures in dendritic cells are maintained upon additional cytomegalovirus exposure.

During the birch pollen season an enhanced incidence of virus infections is noticed, raising the question whether pollen can affect anti-viral responses independent of allergic reactions. We previously showed that birch pollen-treatment of monocyte-derived dendritic cells (moDC) enhances human cytomegalovirus (HCMV) infection. Here we addressed how in moDC the relatively weak pollen response can affect the comparably strong response to HCMV. To this end, moDC were stimulated with aqueous birch pollen extract (APE), HCMV, and APE with HCMV, and transcriptomic signatures were determined after 6 and 24 h of incubation. Infection was monitored upon exposure of moDC to GFP expressing HCMV by flow cytometric analysis of GFP expressing cells. Principle component analysis of RNA sequencing data revealed close clustering of mock and APE treated moDC, whereas HCMV as well as APE with HCMV treated moDC clustered separately after 6 and 24 h of incubation, respectively. Communally induced genes were detected in APE, HCMV and APE with HCMV treated moDC. In APE with HCMV treated moDC, the comparably weak APE induced signatures were maintained after HCMV exposure. In particular, NF-κB/RELA and PI3K/AKT/MAPK signaling were altered upon APE with HCMV exposure. Earlier, we discovered that NF-κB inhibition alleviated APE induced enhancement of HCMV infection. Here we additionally found that impairment of PI3K signaling reduced HCMV infection in HCMV and APE with HCMV treated moDC. APE treated moDC that were exposed to HCMV show a unique host gene signature, which to a large extent is regulated by NF-κB activation and PI3K/AKT/MAPK signaling.

Evaluating birch leaf tea as a functional herbal beverage: Beneficial impact on the urinary tract, and metabolism in human organism.

Herbal teas are considered as a potential constituent of novel functional beverages consumed daily. One of the commonly used herbal teas is silver birch (Betula pendula Roth) leaf infusion, traditionally used in urinary tract diseases. In this study, the potential of birch leaf infusion as a functional beverage, emphasizing its active ingredients' bioavailability, anti-inflammatory, and antiadhesive properties concerning urinary tract health, was investigated. A complex approach was proposed, which included phytochemical screening, bioavailability, gut microbiota biotransformation, and an in vivo test for urine metabolomics assessment. The bioassays confirmed significant anti-inflammatory (interleukins IL-6 and IL-8 secretion) and anti-adhesive (Uropathogenic Escherichia coli and T24 bladder cells) activities. The high-resolution mass spectrometry metabolomics studies linked gut microbiota metabolites and the metabolites present in the urine. Several metabolites connected with phenolics' consumption were detected in the urine, e.g., glucuronides and sulfates of caffeic acid and dihydroxyphenyl-γ-valerolactones. Based on the presented results, the birch leaf should be considered useful in designing functional beverages, especially targeted to the groups at high risk of urinary diseases.

Contrasting water-use strategies to climate warming in white birch and larch in a boreal permafrost region.

The effects of rising atmospheric CO2 concentrations (Ca) with climate warming on intrinsic water-use efficiency and radial growth in boreal forests are still poorly understood. We measured tree-ring cellulose δ13C, δ18O, and tree-ring width in Larix dahurica (larch) and Betula platyphylla (white birch), and analyzed their relationships with climate variables in a boreal permafrost region of northeast China over past 68 years covering a pre-warming period (1951-1984; base period) and a warm period (1985-2018; warm period). We found that white birch but not larch significantly increased their radial growth over the warm period. The increased intrinsic water-use efficiency in both species was mainly driven by elevated Ca but not climate warming. White birch but not larch showed significantly positive correlations between tree-ring δ13C, δ18O and summer maximum temperature as well as vapor pressure deficit in the warm period, suggesting a strong stomatal response in the broad-leaved birch to temperature changes. The climate warming-induced radial growth enhancement in white birch is primarily associated with a conservative water-use strategy. In contrast, larch exhibits a profligate water-use strategy. It implies an advantage for white birch over larch in the warming permafrost regions.

Continental-scale evaluation of downy birch pollen production: Estimating the impacts of global change.

The high prevalence of hay fever in Europe has raised concerns about the implications of climate change-induced higher temperatures on pollen production. Our study focuses on downy birch pollen production across Europe by analyzing 456 catkins during 2019-2021 in 37 International Phenological Gardens (IPG) spanning a large geographic gradient. As IPGs rely on genetically identical plants, we were able to reduce the effects of genetic variability. We studied the potential association with masting behavior and three model specifications based on mean and quantile regression to assess the impact of meteorology (e.g., temperature and precipitation) and atmospheric gases (e.g., ozone (O3) and carbon-dioxide (CO2)) on pollen and catkin production, while controlling for tree age approximated by stem circumference. The results revealed a substantial geographic variability in mean pollen production, ranging from 1.9 to 2.5 million pollen grains per catkin. Regression analyses indicated that elevated average temperatures of the previous summer corresponded to increased pollen production, while higher O3 levels led to a reduction. Additionally, catkins number was positively influenced by preceding summer's temperature and precipitation but negatively by O3 levels. The investigation of quantile effects revealed that the impacts of mean temperature and O3 levels from the previous summer varied throughout the conditional response distribution. We found that temperature predominantly affected trees characterized by a high pollen production. We therefore suggest that birches modulate their physiological processes to optimize pollen production under varying temperature regimes. In turn, O3 levels negatively affected trees with pollen production levels exceeding the conditional median. We conclude that future temperature increase might exacerbate pollen production while other factors may modify (decrease in the case of O3 and amplify for precipitation) this effect. Our comprehensive study sheds light on potential impacts of climate change on downy birch pollen production, which is crucial for birch reproduction and human health.

Physiological and psychological recovery in two pure forests: interaction between perception methods and perception durations.

The forest experience is good for people's physical and mental health. However, few studies on the effects of pure forest based on the duration and way of experience on people's physical and mental recovery. In this study, we took 180 first-year college students as research objects and conducted experiments in Pinus sylvestris and Betula platyphylla and the control group of grass plot. The changes of physiological and psychological indexes of the subjects were compared by two perception methods (onsite perception, video perception) and three perception duration (10 min, 20 min, 30 min). The results indicated that: (1) Differences between the two pure forests were mainly reflected in short-term recovery of diastolic blood pressure (DBP) and long-term recovery of total mood disorder (TMD). (2) Video perception was more conducive to short-term recovery of systolic blood pressure (SBP) and diastolic blood pressure (DBP). (3) Viewing the Pinus sylvestris for 20 min in different ways was the best way to relieve stress. It is suggested that, Pinus sylvestris can be used as the rehabilitation perception material, and reasonable path length or perception time can be selected for landscape construction in future. These results can provide scientific reference for landscape design based on forest health and environmental perception.

Complex Polyploids: Origins, Genomic Composition, and Role of Introgressed Alleles.

Introgression allows polyploid species to acquire new genomic content from diploid progenitors or from other unrelated diploid or polyploid lineages, contributing to genetic diversity and facilitating adaptive allele discovery. In some cases, high levels of introgression elicit the replacement of large numbers of alleles inherited from the polyploid's ancestral species, profoundly reshaping the polyploid's genomic composition. In such complex polyploids, it is often difficult to determine which taxa were the progenitor species and which taxa provided additional introgressive blocks through subsequent hybridization. Here, we use population-level genomic data to reconstruct the phylogenetic history of Betula pubescens (downy birch), a tetraploid species often assumed to be of allopolyploid origin and which is known to hybridize with at least four other birch species. This was achieved by modeling polyploidization and introgression events under the multispecies coalescent and then using an approximate Bayesian computation rejection algorithm to evaluate and compare competing polyploidization models. We provide evidence that B. pubescens is the outcome of an autoploid genome doubling event in the common ancestor of B. pendula and its extant sister species, B. platyphylla, that took place approximately 178,000-188,000 generations ago. Extensive hybridization with B. pendula, B. nana, and B. humilis followed in the aftermath of autopolyploidization, with the relative contribution of each of these species to the B. pubescens genome varying markedly across the species' range. Functional analysis of B. pubescens loci containing alleles introgressed from B. nana identified multiple genes involved in climate adaptation, while loci containing alleles derived from B. humilis revealed several genes involved in the regulation of meiotic stability and pollen viability in plant species.