Betula Platyphylla Var Research Articles

Elevated ozone alters long-chain fatty acids in leaves of Japanese white birch saplings.

Long-chain fatty acids (LCFAs) in leaves have attracted attention as nutritious phytochemicals and olfactory signals that influence the behavior and growth of herbivorous insects. In recognition of the negative effects of increasing tropospheric ozone (O3) levels on plants, LCFAs can be altered through peroxidation by O3. However, how elevated O3 changes the amount and composition of LCFAs in field-grown plants is still unknown. We investigated palmitic, stearic, oleic, linoleic, linolenic LCFAs in the two leaf types (spring and summer) and two stages (early and late stage after expansion) of Japanese white birch (Betula platyphylla var. japonica) after a multi-year O3 exposure on the field. Summer leaves exhibited a distinct composition of LCFAs under elevated O3 at the early stage, whereas both stages of spring leaves did not exhibit significant changes in LCFAs composition by elevated O3. In the spring leaves, the amounts of saturated LCFAs significantly increased at the early stage, however, the amount of total, palmitic, and linoleic acids at the late stage were significantly decreased by elevated O3. Summer leaves had a lower amount of all LCFAs at both leaf stages. Regarding the early stage of summer leaves, the lower amount of LCFAs under elevated O3 was possibly due to O3-suppressed photosynthesis in the current spring leaves. Furthermore, the decrease ratio of spring leaves over time was significantly increased by elevated O3 in all LCFAs, whereas summer leaves did not exhibit such an effect. These findings suggest that further studies should be conducted to reveal the biological functions of LCFAs under elevated O3, considering the leaf type- and stage-dependent changes of LCFAs.

THE RELATIONSHIP BETWEEN BULK DENSITY AND THERMAL CONDUCTIVITY IN VARIOUS KOREAN WOODS

The article deals with the effects of bulk density on thermal conductivity in specimens of 15Korean woods (Zelkova serrata, Pinus densiflora, Cornus controversa, Betula schmidtii, Betula platyphylla var. japonica, Ginkgo biloba L.,Cedrela sinensis A. Juss., Fraxinus mandshurica, Ulmus davidiana var. japonica, Prunus sargentii Rehder, Paulownia tomentosa (Thunb.) Steud., Larix kaempferi (Lamb.) Carrière, Robinia pseudoacacia, Kalopanax septemlobus and Tilia amurensis).The results of this study were compared with previous studies performed on wood specimens fromChina, India, and Turkey. Consistent with these previous studies, bulk density and thermal conductivity were positively correlated in Korean woods, and a simple regression model with a very high correlation of R2(94%) was obtained. Interestingly, we observed some variation between our simple regression models and those generated by previous researchers who had examined non-Korean woods.

Photosynthetic and Growth Responses in a Pioneer Tree (Japanese White Birch) and Competitive Perennial Weeds (Eupatorium sp.) Grown Under Different Regimes With Limited Water Supply to Waterlogging.

For a successful natural regeneration of Japanese white birch (Betula platyphylla var. japonica), competitive vegetation should be managed. Here, we clarified how soil water condition modifies the competitiveness of Japanese white birch against perennial weeds, Eupatorium species, based on an ecophysiological approach combining a glasshouse experiment and a field survey. We investigated photosynthetic and growth responses to various water regimes from water deficit to waterlogging (two times-a-week irrigation, three times-a-week irrigation, half waterlogging, and full waterlogging) in pot-grown seedlings of Japanese white birch and the competitive weed Eupatorium makinoi. The ratio of seedling height of Japanese white birch to seedling height of E. makinoi showed a decreasing trend from two times-a-week irrigation to full waterlogging, which suggests a lower competitiveness for light resource in Japanese white birch with increasing soil wetness. The maximum rate of Rubisco carboxylation (Vc,max) based on unit N was lower in waterlogging treatments than in two times- and three times-a-week irrigation in Japanese white birch, whereas E. makinoi showed the opposite response. This suggests that N partitioning into Rubisco and/or Rubisco activation might be suppressed in Japanese white birch but enhanced in E. makinoi under waterlogging. The maximum photochemical efficiency of photosystem II (Fv/Fm) was also lower in seedlings of Japanese white birch grown under waterlogging treatments. We further conducted a field survey on the relationship between Fv/Fm and topographic wetness index (TWI) in seedlings of Japanese white birch and E. glehnii (closely related to E. makinoi) naturally grown in a study site 5 years after canopy tree cutting. Lower Fv/Fm was observed in seedlings of Japanese white birch with increasing TWI, whereas no significant trend was observed in E. glehnii, in agreement with the glasshouse experiment. Thus, keeping soils not always humid might be favorable to photosynthetic performance and growth competitive ability of Japanese white birch against Eupatorium species.

Succession of Ambrosia Beetles Colonizing the Logs of Fallen Alder and Birch Trees.

Simple SummaryTo determine the succession of ambrosia beetles after tree felling, two Betulaceae tree species, an alder (Alnus hirsuta), and a white birch (Betula platyphylla var. japonica) were felled as bait logs in central Hokkaido, Japan, in 2016. From 2016 to 2018, the bait logs were dissected late in each flying season to collect ambrosia beetles. During the period of monitoring, most beetles were collected during the first 2 years. The ambrosia beetle faunas colonizing the two plant species were found to be similar, and it was established that each beetle species appeared in the same sequence in each of the two plant species, albeit with differing temporal patterns. These observations thus indicate a similar sequence of beetle succession in the two tree species, and that the relative niches of beetle species in the successional sequence after tree felling can be determined using this methodology.Ambrosia beetles bore into the xylem of woody plants, reduce timber quality, and can sometimes cause devastating damage to forest ecosystems. The colonization by different beetle species is dependent on host status, from healthy trees to the early stages of wood decay, although the precise factors influencing their host selection are not well known. Classic studies on plant ecology have determined the niches of different plant species in vegetation succession, based on comparisons of successions in different locations using ordination analyses, although the factors influencing the colonization of each species are largely undetermined. In this study, to characterize the succession of ambrosia beetles after tree felling, two Betulaceae tree species, an alder (Alnus hirsuta), and a white birch (Betula platyphylla var. japonica) were felled as bait logs in central Hokkaido, Japan, in 2016. From 2016 to 2018, the bait logs were dissected late in each flying season, and ambrosia beetles were collected from the logs. During the period of monitoring, the beetle colonization in both tree species was mostly concentrated in the first 2 years. We observed similarities in the beetle faunas colonizing the two plant species, and that individual species appeared in the same sequence in the logs of the two plant species, although the temporal patterns of colonization differed. Consequently, significant differences in beetle community compositions in the two host species were detected in each of the first 2 years of the study, whereas the difference in the overall composition of beetle assemblages (=pooled over 3 years) between the two plant species was smaller than that in either 2016 or 2017. We speculated that the differences in the temporal pattern of colonization could be attributable to differences in the rates at which the wood of the two tree species deteriorated. Treptoplatypus severini and Xylosandrus crassiusculus were considered to be early-successional species that commenced log colonization soon after felling, although T. severini has a wide niche and was collected during all 3 years of the study. Conversely, Xyleborinus attenuatus and Heteroborips seriatus were identified as probable late-successional species that showed a preference for older logs.

Degradation of White Birch Shelterbelts by the Attack of White-Spotted Longicorn Beetles in Central Hokkaido, Northern Japan

A widespread decline of white birch (Betula platyphylla var. japonica) shelterbelts was observed in central Hokkaido, Japan. Many exit holes bored by white-spotted longicorn beetles (Anoplophora malasiaca) were found at the base of the trunks of trees in these stands. The present study aims to evaluate the effects of infestation on the degradation, and demonstrates whether the number of exit holes (Nholes) can be used as an index of the decline of trees. We selected 35 healthy appearing stands and 16 degraded stands in the study area. A generalized linear mixed model with zero inflation revealed that Nholes of standing dead trees tended to be greater than that of living trees, and the tree vigor decreased with increasing Nholes. These results implied that the degradation of the shelterbelts was caused by the beetle. We also found size-dependent mortality, i.e., only a few larvae can cause the death of smaller trees, but not larger trees. Furthermore, evaluation of the degradation at the stand level (Nholes) using a logistic regression analysis revealed that the degradation at the stand level could be predicted by Nholes. Our findings can be used as a useful index marker for diagnosing white birch shelterbelts.

Plant-insect communication in urban forests: Similarities of plant volatile compositions among tree species (host vs. non-host trees) for alder leaf beetle Agelastica coerulea

Behavior of insects, such as pollination and grazing, is usually determined by biogenic volatile organic compounds (BVOCs). However, particularly in O3-polluted urban forests, the BVOCs-based plant-insect communication can be disrupted by the reaction of O3 with leaf-emitted BVOCs, such as between Japanese white birch (Betula platyphylla var. japonica) and a leaf beetle (Agelastica coerulea). To understand plant-insect communication in O3-polluted environments, it is necessary to identify chemical species of BVOCs that contribute to attractiveness toward insects but are diminished by elevated O3. In this study, we conducted olfactory response tests and gas chromatography mass spectrometry (GC-MS) analyses to clarify whether there is a similarity of BVOC components among Betulaceae host trees that can explain the attraction of the stenophagous insect A. coerulea. The olfactory response tests indicated that Betulaceae host trees attract A. coerulea via leaf-emitted BVOCs, while there was no preference of the leaf beetles to non-host trees (Sorbus commixta and Morus bombycis). However, GC-MS analyses indicated that the composition of BVOC blends considerably differed among Betulaceae host trees, although alders (Alnus hirsuta and A. japonica) had a similar composition of BVOC blend in each season (June and September) during which the adult leaf beetle is active. A distinct characteristic of the emission from B. platyphylla was that 2-carene and limonene, which are O3-reactive species, were emitted with a high monoterpene ratio irrespective of the season. Thus, these volatiles and the blend could be expected to lead the disrupted communication found between B. platyphylla and A. coerulea under elevated O3 in previous field studies. In addition, our results indicated that A. coerulea is attracted to more than one blend within Betulaceae host trees, suggesting that grazing damages can be affected by different host preferences and O3 reactivity with specific BVOCs in the field. BVOCs-based plant-insect interactions should be further studied in multi-species communities to better understand plant-insect communication in O3-polluted environments.

Genome-wide analysis of BpDof genes and the tolerance to drought stress in birch (Betula platyphylla).

BackgroundDNA binding with one finger (Dof) proteins are plant-specific transcription factors playing vital roles in developmental processes and stress responses in plants. Nevertheless, the characterizations, expression patterns, and functions of the Dof family under drought stress (a key determinant of plant physiology and metabolic homeostasis) in woody plants remain unclear.MethodsThe birch (Betula platyphylla var. mandshuric) genome and plant TFDB database were used to identify Dof gene family members in birch plants. ClustalW2 of BioEdit v7.2.1, MEGA v7.0, ExPASy ProtParam tool, Subloc, TMHMM v2.0, GSDS v2.0, MEME, TBtools, KaKs Calculator v2.0, and PlantCARE were respectively used to align the BpDof sequences, build a phylogenetic tree, identify the physicochemical properties, analyze the chromosomal distribution and synteny, and identify the cis-elements in the promoter regions of the 26 BpDof genes. Additionally, the birch seedlings were exposed to PEG6000-simulated drought stress, and the expression patterns of the BpDof genes in different tissues were analyzed by qRT-PCR. The histochemical staining and the evaluation of physiological indexes were performed to assess the plant tolerance to drought with transient overexpression of BpDof4, BpDof11, and BpDof17 genes. SPSS software and ANOVA were used to conduct all statistical analyses and determine statistically significant differences between results.ResultsA total of 26 BpDof genes were identified in birch via whole-genome analysis. The conserved Dof domain with a C(x)2C(x)21C(x)2C zinc finger motif was present in all BpDof proteins. These birch BpDofs were classified into four groups (A to D) according to the phylogenetic analysis of Arabidopsis thaliana Dof genes. BpDof proteins within the same group mostly possessed similar motifs, as detected by conserved motif analysis. The exon–intron analysis revealed that the structures of BpDof genes differed, indicating probable gene gain and lose during the BpDof evolution. The chromosomal distribution and synteny analysis showed that the 26 BpDofs were unevenly distributed on 14 chromosomes, and seven duplication events among six chromosomes were found. Cis-acting elements were abundant in the promoter regions of the 26 BpDof genes. qRT-PCR revealed that the expression of the 26 BpDof genes was differentially regulated by drought stress among roots, stems, and leaves. Most BpDof genes responded to drought stress, and BpDof4, BpDof11, and BpDof17­ were significantly up-regulated. Therefore, plants overexpressing these three genes were generated to investigate drought stress tolerance. The BpDof4-, BpDof11-, and BpDof17­-overexpressing plants showed promoted reactive oxygen species (ROS) scavenging capabilities and less severe cell damage, suggesting that they conferred enhanced drought tolerance in birch. This study provided an in-depth insight into the structure, evolution, expression, and function of the Dof gene family in plants.

Growth and Photosynthetic Responses of Seedlings of Japanese White Birch, a Fast-Growing Pioneer Species, to Free-Air Elevated O3 and CO2

Plant growth is not solely determined by the net photosynthetic rate (A), but also influenced by the amount of leaves as a photosynthetic apparatus. To evaluate growth responses to CO2 and O3, we investigated the effects of elevated CO2 (550–560 µmol mol−1) and O3 (52 nmol mol−1; 1.7 × ambient O3) on photosynthesis and biomass allocation in seedlings of Japanese white birch (Betula platyphylla var. japonica) grown in a free-air CO2 and O3 exposure system without any limitation of root growth. Total biomass was enhanced by elevated CO2 but decreased by elevated O3. The ratio of root to shoot (R:S ratio) showed no difference among the treatment combinations, suggesting that neither elevated CO2 nor elevated O3 affected biomass allocation in the leaf. Accordingly, photosynthetic responses to CO2 and O3 might be more important for the growth response of Japanese white birch. Based on A measured under respective growth CO2 conditions, light-saturated A at a light intensity of 1500 µmol m−2 s−1 (A1500) in young leaves (ca. 30 days old) exhibited no enhancement by elevated CO2 in August, suggesting photosynthetic acclimation to elevated CO2. However, lower A1500 was observed in old leaves (ca. 60 days old) of plants grown under elevated O3 (regulated to be twice ambient O3). Conversely, light-limited A measured under a light intensity of 200 µmol m−2 s−1 (A200) was significantly enhanced by elevated CO2 in young leaves, but suppressed by elevated O3 in old leaves. Decreases in total biomass under elevated O3 might be attributed to accelerated leaf senescence by O3, indicated by the reduced A1500 and A200 in old leaves. Increases in total biomass under elevated CO2 might be attributed to enhanced A under high light intensities, which possibly occurred before the photosynthetic acclimation observed in August, and/or enhanced A under limiting light intensities.

Inhibitory Effect of (2R)-4-(4-hydroxyphenyl)-2-butanol 2-O-β-d-apiofuranosyl-(1→6)-β-d-glucopyranoside on RANKL-Induced Osteoclast Differentiation and ROS Generation in Macrophages.

In bone homeostasis, bone loss due to excessive osteoclasts and inflammation or osteolysis in the bone formation process cause bone diseases such as osteoporosis. Suppressing the accompanying oxidative stress such as ROS in this process is an important treatment strategy for bone disease. Therefore, in this study, the effect of (2R)-4-(4-hydroxyphenyl)-2-butanol 2-O-β-d-apiofuranosyl-(1→6)-β-d-glucopyranoside (BAG), an arylbutanoid glycoside isolated from Betula platyphylla var. japonica was investigated in RANKL-induced RAW264.7 cells and LPS-stimulated MC3E3-T1 cells. BAG inhibited the activity of TRAP, an important marker of osteoclast differentiation and F-actin ring formation, which has osteospecific structure. In addition, the protein and gene levels were suppressed of integrin β3 and CCL4, which play an important role in the osteoclast-induced bone resorption and migration of osteoclasts, and inhibited the production of ROS and restored the expression of antioxidant enzymes such as SOD and CAT lost by RANKL. The inhibitory effect of BAG on osteoclast differentiation and ROS production appears to be due to the inhibition of MAPKs phosphorylation and NF-κβ translocation, which play a major role in osteoclast differentiation. In addition, BAG inhibited ROS generated by LPS and effectively restores the mineralization of lost osteoblasts, thereby showing the effect of bone formation in the inflammatory situation accompanying bone loss by excessive osteoclasts, suggesting its potential as a new natural product-derived bone disease treatment.

Arable land windbreak forests to reduce the impacts of fallen branches and branchlets from larch

In the Tokachi plain of eastern Hokkaido, Japanese larch, Larix kaempferi, is often planted in arable land windbreaks to prevent wind damage to sugar beets,potatoes, and beans during the spring cultivation season. Japanese larch is fast-growing and very effective in reducing wind damage in the early spring cultivation season, even if its buds are not open or its leaves are not fully extended. However, many farmers dislike Japanese larch arable land windbreaks because they shed a lot of branches and branchlets to cultivation fields every year, which may cause damage to agricultural tractors. Therefore, it is necessary to suggest a model of arable land windbreaks with less amount of fallen branches and branchlets of larches entering the cultivation field. It is recommended to plant three rows of trees: Japanese larch in the most windward and middle rows, and Japanese white birch, Betula platyphyllavar. japonica, in the most leeward row. Japanese larch in the most windward and middle rows reduces wind speed, whereas Japanese white birch in the most leeward row reduces branches and branchlets of Japanese larch entering cultivation fields.

Impact Assessment of Ozone Absorbed through Stomata on Photosynthetic Carbon Dioxide Uptake by Japanese Deciduous Forest Trees: Implications for Ozone Mitigation Policies

Photosynthesis by trees is expected to contribute to preventing climate change including global warming. However, the current levels of tropospheric ozone (O3) reduce the uptake of photosynthetic carbon dioxide (CO2) by forest trees in Japan, which is a concern. Furthermore, it is unknown how much O3 should be reduced to prevent plants’ O3-induced damage. The objective of the present study was to assess the negative effects of the current levels of O3 absorbed via stomata and the impact of its mitigation on the CO2 uptake by trees in Japanese forests. Impact assessment, targeted in 2011–2015, was performed for four deciduous broad-leaved trees: Fagus crenata, Quercus serrata, Q. mongolica var. crispula, and Betula platyphylla var. japonica. The assessment was based on species-specific cumulative stomatal O3 uptake (COU) and species-specific responses of annual photosynthetic CO2 uptake to COU. Annual COU differed between the four trees; the average COU of F. crenata, Q. serrata, Q. mongolica var. crispula, and B. platyphylla var. japonica across Japan was 41.7, 26.5, 33.0, and 29.1 mmol m−2, respectively, and the reductions in CO2 uptake by the four trees were 14.0%, 10.6%, 8.6%, and 15.4%, respectively. Further analysis revealed that reducing the atmospheric O3 concentration by approximately 28%, 20%, 17%, and 49% decreased the O3-induced reductions in photosynthetic CO2 uptake to 5% in F. crenata, Q. serrata, Q. mongolica var. crispula, and B. platyphylla var. japonica, respectively. In the near future, implementing mitigation measures for the O3 damage in plants is expected to enhance the photosynthetic capacity of Japanese forest tree species.

Does Ozone Alter the Attractiveness of Japanese White Birch Leaves to the Leaf Beetle Agelastica coerulea via Changes in Biogenic Volatile Organic Compounds (BVOCs): An Examination with the Y-Tube Test

Elevated ground-level ozone (O3) reduced C-based defense chemicals; however, severe grazing damages were found in leaves grown in the low O3 condition of a free air O3-concentration enrichment (O3-FACE) system. To explain this phenomenon, this study investigates the role of BVOCs (biogenic volatile organic compounds) as signaling compounds for insect herbivores. BVOCs act as scents for herbivore insects to locate host plants, while some BVOCs show high reactivity to O3, inducing changes in the composition of BVOCs in atmospheres with elevated O3. To assess the aforementioned phenomenon, profiles of BVOCs emitted from birch (Betula platyphylla var. japonica Hara) leaves were analyzed ex situ, and Y-tube insect preference tests were conducted in vitro to study the insect olfactory response. The assays were conducted in June and August or September, according to the life cycle of the adult alder leaf beetle Agelastica coerulea Baly (Coleoptera: Chrysomelidae). The Y-tube tests revealed that the leaf beetles were attracted to BVOCs, and O3 per se had neither an attractant nor a repellent effect. BVOCs became less attractant when mixed with highly concentrated O3 (>80 ppb). About 20% of the total BVOCs emitted were highly O3-reactive compounds, such as β-ocimene. The results suggest that BVOCs emitted from the birch leaves can be altered by elevated O3, thus potentially reducing the attractiveness of leaves to herbivorous insects searching for food.

Succession of litter-decomposing microbial organisms in deciduous birch and oak forests, northern Japan

Biological litter decomposition and the litter-associated microbial organisms were monitored for three years to characterize litter decomposition in early and late successional stages. Two forests were used for the investigation: pioneer a forest dominated by birch (Betula platyphylla var. japonica) and a climax forest by oak (Quercus mongolica var. grosseserrata) in the cool-temperate region of northern Japan. Three types of litter were used: birch, oak and mixed litter. The litter decomposition was effective during the first year but 50% of the original litter remained even after three years. Carbon-to-nitrogen ratios in the litter decreased largely in the first year and became stable thereafter. The litter decomposition rates were not different among the litter types and between the forests. The temporal changes in phospholipid fatty acids (PLFAs) showed that fungal biomass reached its peak in the first year and the bacterial biomass increased steadily until the end of the experiment. The concentrations of fungal PLFAs in the litter did not differ between the litter types but were lower in the oak forest. The litter decomposition was performed mostly by fungi, in particular in the early stages, while bacterial decomposition depended on the litter types and/or the forest types. Gram-negative bacteria reached their peak of PLFAs in the second year while gram-positive bacteria PLFAs increased gradually during the three years. Therefore, the succession of microorganisms in the litter occurred from fungi to bacteria and from gram-negative bacteria to gram-positive bacteria in the two forests. Unlike in the case of coniferous or monotonic forests, the effects of forests and litter types on litter decomposition for the first year were weak. The forest types on litter decomposition appeared only for the long-term litter decomposition. The successional changes of microorganisms occurred from fungi to bacteria for long-term litter decomposition processes with increasing N concentration in the litter.

Evaluation of O3 Effects on Cumulative Photosynthetic CO2 Uptake in Seedlings of Four Japanese Deciduous Broad-Leaved Forest Tree Species Based on Stomatal O3 Uptake

The current level of tropospheric ozone (O3) is expected to reduce the net primary production of forest trees. Here, we evaluated the negative effects of O3 on the photosynthetic CO2 uptake of Japanese forest trees species based on their cumulative stomatal O3 uptake, defined as the phytotoxic O3 dose (POD). Seedlings of four representative Japanese deciduous broad-leaved forest tree species (Fagus crenata, Quercus serrata, Quercus mongolica var. crispula and Betula platyphylla var. japonica) were exposed to different O3 concentrations in open-top chambers for two growing seasons. The photosynthesis–light response curves (A-light curves) and stomatal conductance were measured to estimate the leaf-level cumulative photosynthetic CO2 uptake (ΣPn_est) and POD, respectively. The whole-plant-level ΣPn_est were highly correlated with the whole-plant dry mass increments over the two growing seasons. Because whole-plant growth is largely determined by the amount of leaf area per plant and net photosynthetic rate per leaf area, this result suggests that leaf-level ΣPn_est, which was estimated from the monthly A-light curves and hourly PPFD, could reflect the cumulative photosynthetic CO2 uptake of the seedlings per unit leaf area. Although the O3-induced reductions in the leaf-level ΣPn_est were well explained by POD in all four tree species, species-specific responses of leaf-level ΣPn_est to POD were observed. In addition, the flux threshold appropriate for the linear regression of the responses of relative leaf-level ΣPn_est to POD was also species-specific. Therefore, species-specific responses of cumulative photosynthetic CO2 uptake to POD could be used to accurately evaluate O3 impact on the net primary production of deciduous broad-leaved trees.

Light Energy Partitioning under Various Environmental Stresses Combined with Elevated CO2 in Three Deciduous Broadleaf Tree Species in Japan

Understanding plant response to excessive light energy not consumed by photosynthesis under various environmental stresses, would be important for maintaining biosphere sustainability. Based on previous studies regarding nitrogen (N) limitation, drought in Japanese white birch (Betula platyphylla var. japonica), and elevated O3 in Japanese oak (Quercus mongolica var. crispula) and Konara oak (Q. serrata) under future-coming elevated CO2 concentrations, we newly analyze the fate of absorbed light energy by a leaf, partitioning into photochemical processes, including photosynthesis, photorespiration and regulated and non-regulated, non-photochemical quenchings. No significant increases in the rate of non-regulated non-photochemical quenching (JNO) were observed in plants grown under N limitation, drought and elevated O3 in ambient or elevated CO2. This suggests that the risk of photodamage caused by excessive light energy was not increased by environmental stresses reducing photosynthesis, irrespective of CO2 concentrations. The rate of regulated non-photochemical quenching (JNPQ), which contributes to regulating photoprotective thermal dissipation, could well compensate decreases in the photosynthetic electron transport rate through photosystem II (JPSII) under various environmental stresses, since JNPQ+JPSII was constant across the treatment combinations. It is noteworthy that even decreases in JNO were observed under N limitation and elevated O3, irrespective of CO2 conditions, which may denote a preconditioning-mode adaptive response for protection against further stress. Such an adaptive response may not fully compensate for the negative effects of lethal stress, but may be critical for coping with non-lethal stress and regulating homeostasis. Regarding the three deciduous broadleaf tree species, elevated CO2 appears not to influence the plant responses to environmental stresses from the viewpoint of susceptibility to photodamage.

Bioactivity evaluations of betulin identified from the bark of Betula platyphylla var. japonica for cancer therapy.

Identification of bioactive natural products with anticancer activity as well as alleviating effects on chemotherapy-induced side effects has significant implications for cancer treatment. Betula platyphylla var. japonica, commonly known as Asian white birch, has been used in Chinese traditional medicine for a variety of purposes. In this study, the medicinal properties of betulin from B. platyphylla var. japonica useful for cancer management were investigated. LC/MS analysis revealed that betulin is a main chemical component of the EtOH extract of B. platyphylla var. japonica bark, and betulin was isolated from EtOH extract using an LC/MS-guided isolation method. Its structure was identified with 1H and 13C NMR spectroscopic data and LC/MS analysis and then compared to the previously reported spectroscopic and physical data. We first verified the cytotoxicity of betulin against three human lung adenocarcinoma cell lines, A549, H1264, and Calu-6, with IC50 values ranging from 18.7 to 39.6μM. Regarding alleviation of side effects associated with anticancer chemotherapy, betulin ameliorated cisplatin-induced renal cell damage to 80% of the control value from the concentration of 5μM. In addition, betulin showed anti-gastritis activity against ethanol-induced gastric damage in rats and notably reduced the gastric damage index compared to control in a concentration-dependent manner. These findings provide the first experimental evidence for potential use of B. platyphylla var. japonica as a functional food for cancer treatment that simultaneously alleviates the side effects of chemotherapy.

Growth and nutrition of Agelastica coerulea (Coleoptera: Chrysomelidae) larvae changed when fed with leaves obtained from an O3-enriched atmosphere.

A series of laboratory no-choice assays were performed to test changes in the feeding, growth, and nutrition of leaf beetle (Agelastica coerulea) larval instars on O3-treated leaves of Japanese white birch (Betula platyphylla var. japonica). Larvae fed with O3-treated leaves grew and developed significantly faster throughout their developmental cycle than the corresponding controls. The growth rate (GR) and consumption index (CI) were mostly decreased with age for both control and O3-treated leaves. Efficiency of conversion of both ingested and digested food (ECI, ECD) showed an increase from the 2nd to the 4th instar, after which they decreased significantly and reached the lowest value in the last larval instars (7th). GR, CI, ECI, and ECD were greater and approximate digestibility (AD) was lower in larvae fed with O3-treated leaves than those fed with control leaves. This indicated that the greater rate of growth on fumigated leaves was due primarily to a greater rate of consumption (i.e., O3 increased the "acceptability" of the host more than "suitability") and efficiency in converting food into body mass. Overall, larval performance seemed to have improved when fed with O3-treated leaves in these assays. This study suggests that insects may be more injurious to O3-treated plants and warrants further investigations on birch-beetle interactions under field conditions.

LC/MS-based Analysis of Bioactive Compounds from the Bark of Betula platyphylla var. japonica and Their Effects on Regulation of Adipocyte and Osteoblast Differentiation

Betula platyphylla var. japonica (Betulaceae), also known as Asian white birch, is an endemic medicinal tree, the bark of which has been used in Chinese traditional medicine for the treatment of various inflammatory diseases. In our continuing search for bioactive compounds from Korean natural resources, a phytochemical investigation of the bark of B. platyphylla var. japonica led to the isolation of 7-oxo-β-sitosterol (1) and soyacerebroside I (2) from its ethanol extract as main components by liquid chromatography (LC)/mass spectrometry (MS)-based analysis. The structures of isolates were identified by comparison of 1H and 13C nuclear magnetic resonance spectroscopic data and physical data with the previously reported values and LC/MS analyses. To the best of our knowledge, this is the first study to demonstrate that the isolated compounds, 7-oxo-β- sitosterol and soyacerebroside I, were isolated in B. platyphylla var. japonica. We examined the effects of the isolates on the regulation of adipocytes and osteoblast differentiation. These isolates (1 and 2) produced fewer lipid droplets compared to the untreated negative control in Oil Red O staining of the mouse mesenchymal stem cell line without altering the amount of alkaline phosphatase staining. The results demonstrated that both compounds showed marginal inhibitory effects on adipocyte differentiation but did not affect osteoblast differentiation.

The effects of phenolic glycosides from Betula platyphylla var. japonica on adipocyte differentiation and mature adipocyte metabolism

Betula platyphylla var. japonica (Betulaceae) has been used traditionally in Asian countries for the treatment of inflammatory diseases. A recent study has reported a phenolic compound, platyphylloside from B. platyphylla, that shows inhibition on adipocyte differentiation and induces lipolysis in 3T3-L1 cells. Based on this finding, we conducted phytochemical analysis of the EtOH extract of the bark of B. platyphylla var. japonica, which resulted in the isolation of phenolic glycosides (1–4). Treatment of the isolated compounds (1–4) during adipocyte differentiation of 3T3-L1 mouse adipocytes resulted in dose-dependent inhibition of adipogenesis. In mature adipocytes, arylbutanoid glycosides (2–4) induced lipolysis related genes HSL and ATGL, whereas catechin glycoside (1) had no effect. Additionally, arylbutanoid glycosides (2–4) also induced GLUT4 and adiponectin mRNA expression, indicating improvement in insulin signaling. This suggests that the isolates from B. platyphylla var. japonica exert benefial effects in regulation of adipocyte differentiation as well as adipocyte metabolism.

Ozone-induced stomatal sluggishness changes stomatal parameters of Jarvis-type model in white birch and deciduous oak.

Stomatal ozone flux is closely related to ozone injury to plants. Jarvis-type multiplicative model has been recommended for estimating stomatal ozone flux in forest trees. Ozone can change stomatal conductance by both stomatal closure and less efficient stomatal control (stomatal sluggishness). However, current Jarvis-type models do not account for these ozone effects on stomatal conductance in forest trees. We examined seasonal course of stomatal conductance in two common deciduous tree species native to northern Japan (white birch: Betula platyphylla var. japonica; deciduous oak: Quercus mongolica var. crispula) grown under free-air ozone exposure. We innovatively considered stomatal sluggishness in the Jarvis-type model using a simple parameter, s, relating to cumulative ozone uptake (defined as POD: phytotoxic ozone dose). We found that ozone decreased stomatal conductance of white birch leaves after full expansion (-28%). However, such a reduction of stomatal conductance by ozone fell in late summer (-10%). At the same time, ozone reduced stomatal sensitivity of white birch to VPD and increased stomatal conductance under low light conditions. In contrast, in deciduous oak, ozone did not clearly change the model parameters. The consideration of both ozone-induced stomatal closure and stomatal sluggishness improved the model performance to estimate stomatal conductance and to explain the dose-response relationship on ozone-induced decline of photosynthesis of white birch. Our results indicate that ozone effects on stomatal conductance (i.e. stomatal closure and stomatal sluggishness) are crucial for modelling studies to determine stomatal response in deciduous trees, especially in species sensitive to ozone.