Bacterial communities and enzyme activities during litter decomposition of Elymus nutans leaf on the Qinghai-Tibet Plateau

The dominant plant litter plays a crucial role in carbon(C)and nutrients cycling as well as ecosystem functions maintenance on the Qinghai-Tibet Plateau(QTP).The impact of litter decomposition of dominant plants on edaphic parameters and grassland productivity has been extensively studied,while its decomposition processes and relevant mechanisms in this area remain poorly understood.We conducted a three-year litter decomposition experiment in the Gansu Gannan Grassland Ecosystem National Observation and Research Station,an alpine meadow ecosystem on the QTP,to investigate changes in litter enzyme activities and bacterial and fungal communities,and clarify how these critical factors regulated the decomposition of dominant plant Elymus nutans(E.nutans)litter.The results showed that cellulose and hemicellulose,which accounted for 95%of the initial lignocellulose content,were the main components in E.nutans litter decomposition.The litter enzyme activities ofβ-1,4-glucosidase(BG),β-1,4-xylosidase(BX),andβ-D-cellobiosidase(CBH)decreased with decomposition while acid phosphatase,leucine aminopeptidase,and phenol oxidase increased with decomposition.We found that both litter bacterial and fungal communities changed significantly with decomposition.Furthermore,bacterial communities shifted from copiotrophic-dominated to oligotrophic-dominated in the late stage of litter decomposition.Partial least squares path model revealed that the decomposition of E.nutans litter was mainly driven by bacterial communities and their secreted enzymes.Bacteroidota and Proteobacteria were important producers of enzymes BG,BX,and CBH,and their relative abundances were tightly positively related to the content of cellulose and hemicellulose,indicating that Bacteroidota and Proteobacteria are the main bacterial taxa of the decomposition of E.nutans litter.In conclusion,this study demonstrates that bacterial communities are the main driving forces behind the decomposition of E.nutans litter,highlighting the vital roles of bacterial communities in affecting the ecosystem functions of the QTP by regulating dominant plant litter decomposition.

The Combination of Achnatherum inebrians Extracts and Soil Microorganisms Inhibited Seed Germination and Seedling Growth in Elymus nutans

In a greenhouse experiment,the effects of soil microorganisms and extracts of Achnatherum inebrians on the seed germination and seedling growth of Elymus nutans were studied.The results showed that both the extracts from aboveground and belowground parts of A.inebrians significantly inhibited the germination rate,germination potential,germination index,vigor index,seedling height,root length,and fresh weight of E.nutans,but increased malondialdehyde content,catalase,peroxidase and superoxide dismutase activity of E.nutans seedlings(p<0.05).The allelopathy of aqueous extracts of the aboveground parts of A.inebrians was stronger than that of the pre-cipitates.Aqueous extracts of the aboveground parts of A.inebrians decreased seed germination rate,germination potential,germination index,vigor index,seedling length,root length,and seedling fresh weight by 10.45%-74.63%,24.18%-32.50%,19.03%-73.36%,37.83%-88.41%,21.42%-53.14%,2.65%-40.21%,and 20.45%-61.36%,respectively,and malondialdehyde content,peroxidase,catalase,and superoxide dismutase activity increased by 8.09%-62.24%,27.83%-86.47%,22.90%-93.17%,and 11.15%-75.91%,respectively.The above indexes were higher in live soil than in sterilized soil.Soil microorganisms increased the allelopathy of A.inebrians.The seed germination rate,germination potential,germination index,vigor index,seedling length,and seedling fresh weight of E.nutans planted in live soil decreased by 8.22%-48.48%,10.00%-51.85%,8.19%-53.26%,16.43%-60.03%,12.91%-28.81%,and 9.09%-22.86%compared with sterilized soil,respectively.Malondialdehyde content,peroxidase,catalase,and superoxide dismutase activity of E.nutans planted in live soil increased by 53.91%-81.06%,15.71%-57.34%,33.33%-86.31%,and 9.78%-52.51%compared with sterilized soil,respectively.The existence of soil microorganisms enhanced the allelopathy of the secondary metabolites of A.inebrians.A combination of microorganisms and aqueous extracts from the aboveground parts of A.inebrians had the strongest allelopathic effect on E.nutans.

Research progress in the study of Clinacanthus nutans and treatment of liver diseases

Background:Based on the long history of medicinal value and modern pharmacological research,a systematic collation of the Clinacanthus nutans has been carried out with a view to providing useful references for the clinical application of the Clinacanthus nutans in hepatoprotection and the research and development of new drugs.Methods:The research progress of a large number of domestic and international studies on the therapeutic mechanism of the antiliver diseases of Clinacanthus nutans and its active ingredients is summarized.The aim is to explore the greater value of the herb.Results:The major chemical constituents with pharmacological activities of the Clinacanthus nutans were summarized,and a feasible mechanism of action was compiled and analyzed.Conclusion:Many studies have confirmed the great medicinal value of Clinacanthus nutans and its active monomer components,especially in the prevention and treatment of liver diseases,which is worthy of more in-depth research,development and utilization.Chinese medicine is the treasure of China,therefore,it should be used in more clinical applications.

Clinacanthus nutans:a review of the medicinal uses,pharmacology and phytochemistry

Clinacanthus nutans Lindau is known as snake grass belonging to the Acanlhaceae family.This plant has diverse and potential medicinal uses in traditional herbal medicine for treating skin rashes,insects and snake bites,lesions caused by herpes simplex virus,diabetes,and gout in Malaysia.Indonesia.Thailand and China.Phylochemieal investigations documented the varied contents of bioaclive compounds from litis plant namely flavonoids,glycosides,glycoglyeerolipids.cerebrosides and monoacylmonogalatosylglycerol.The pharmacological experiment proved that various types of extracts and pure compounds from this species exhibited a broad range of biological properties such as anti-inflammatory,antiviral,antioxidant,and anti-diabetic activities.The lindings of toxicity study showed that extracts from this plant did not show any toxicity thus it can be used as strong therapeutic agents for specific diseased conditions.However,further experiments on chemical components and their mode of action showing biological activities are required to elucidate the complete phytochemical profile and assess to confirm their suitability tor future drugs.This review summarizes the medicinal uses,phytochemistry and pharmacology of this plant in order to explore its therapeutic potential and gaps necessitating for prospected research work.

The identities and anti-herpes simplex virus activity of Clinacanthus nutans and Clinacanthus siamensis

Objective:To distinguish the difference among the Clinacanthus nutans(Burm.f.)Lindau(C.nutans)and Clinacanthus siamensis Bremek(C.siamensis)by assessing pharmacognosy characteristics,molecular aspect and also to evaluate their anti-herpes simplex virus(HSV)type 1 and type 2 activities.Methods:Macroscopic and microscopic evaluation were performed according to WHO Geneva guideline.Stomatal number,stomatal index and palisade ratio of leaves were evaluated.Genomic DNA was extracted by modified CTAB method and ITS region was amplified using PGR and then sequenced.Dry leaves were subsequently extracted with n-hexane,dichloromethane and methanol and antiviral activity was performed using plaque reduction assay and the cytotoxicity of the extracts on Vero cells was determined by MTT assay.Results:Cross section of midrib and stem showed similar major components.Leaf measurement index of stomatal number,stomatal index and palisade ratio of C.nutans were 168.32±29.49,13.83±0.86 and 6.84±0.66,respectively,while C.siamensis were 161.60±18.04,11.93±0.81and 3.37±0.31,respectively.The PCR amplification of ITS region generated the PGR product approximately 700 bp in size.There were 34 polymorphisms within the ITS region which consisted of 11 Indels and 23 nucleotide substitutions.The IC_(50)values of C.nutans extracted with n-hexane,dichloromethane and methanol against HSV-1 were(32.05±3.63)μg/mL,(44.50±2.66)μg/mL,(64.93±7.00)μg/mL,respectively where as those of C.siamensis were(60.00±11.61)μg/mL,(55.69+4.41)μg/mL,(37.39±5.85)μg/mL,respectively.Anti HSV-2 activity of n-hexane,dichloromethane and methanol C.nutans leaves extracts were(72.62±12.60)μg/mL,(65.19±21.45)μg/mL,(65.13±2.22)μg/mL,respectively where as those of C.siamensis were(46.52±4.08)μg/mL,(49.63±2.59)μg/mL,(72.64±6.52)μg/mL,respectively.Conclusions:The combination of macroscopic,microscopic and biomolecular method are able to authenticate these closely related plants and both of them have a potency to be an anti-HSV agent.

Anti-herpes simplex virus activities of monogalactosyl diglyceride and digalactosyl diglyceride from Clinacanthus nutans, a traditional Thai herbal medicine

Objective: To evaluate the monogalactosyl diglyceride(MGDG) and digalactosyl diglyceride(DGDG) from Clinacanthus nutans(C. nutans) for their in vitro antiviral activities against herpes simplex virus type 1(HSV-1) and type 2(HSV-2) by plaque reduction assay.Methods: MGDG and DGDG were extracted with chloroform from C. nutans leaves.MGDG and DGDG were separated from chloroform crude extract using column chromatography, characterized by thin layer chromatography and quantified by high performance liquid chromatography. The anti HSV-1 and 2 activity against pre-treatment and posttreatment of the compounds was evaluated using plaque reduction assay. The cytotoxicity of the extract and the compounds on Vero cells were performed by MTT assay.Results: MGDG and DGDG obtained by column chromatography showed identical profiles as standard MGDG and standard DGDG using thin layer chromatography and high performance liquid chromatography. MGDG and DGDG from C. nutans showed 100%inhibition of HSV-1 replication at the post step of infection at noncytotoxic concentration with IC50 values of 36.00 and 40.00 mg/m L, and HSV-2 at 41.00 and 43.20 mg/mL,respectively. Moreover, MGDG and DGDG from C. nutans were demonstrated to have antiherpes simplex activity at the same level as standard synthetic compounds. In contrast, pretreatment of Vero cells with MGDG and DGDG before HSV-1 and HSV-2 infection did not show inhibitory effect against these viruses. MGDG and DGDG exhibited antiviral activity against HSV-1 with selectivity index of 26.00 and 23.00 and HSV-2 of 23.30 and 21.30.Conclusions: MGDG and DGDG from C. nutans, a traditional Thai herbal medicine illustrated inhibitory activity against HSV-1 and HSV-2, probably by inhibiting the late stage of multiplication, suggesting their promising use as anti-HSV agents.

High molecular karyotype variation revealed in indigenous Elymus nutans in the Qinghai Plateau

The karyotypes of 27 individuals of Elymus nutans from eight wild populations in the Qinghai Plateau were analyzed using sequential FISH and GISH. High FISH pattern polymorphism and karyotype variation were detected within and among populations. The chromosome variations were mainly characterized as repeat deletions and amplifications along with inter-genomic translocations. The chromosomes of the St and Y genomes demonstrated higher polymorphism than those of the H genome. Six different intergenomic translocations were identified in 33.3% of individuals; type Ⅰ and Ⅱ translocations were detected with higher frequency. Further analysis revealed that type Ⅰ and Ⅱ translocations were distributed in different geographic regions. The origin of high karyotype variation of E. nutans in the Qinghai plateau is further discussed.

Leaf gas exchange and photosynthesis curves of Elymus nutans and Potentilla anserina under fencing and grazing conditions in the Qilian Mountains, Northwest China

Potentilla anserina L.and Elymus nutans Griseb.are dominant species in the subalpine meadows of China.Grazing is one of the most important factors that influence community structure and productivity of subalpine meadows.Understanding how grazing changes photosynthetic capability is essential for preservation and restoration of grasslands.However,information about the effects of grazing on photosynthetic capability remains inadequate.Experiments were conducted in fencing and grazing areas in the Qilian Mountains,Northwest China.The leaf gas exchange and photosynthetic curves of P.anserina and E.nutans were measured at different growth stages.Results showed that grazing decreased the values of leaf gas exchange parameters,such as net photosynthetic rate,stomatal conductance,transpiration rate,and intercellular CO2 concentration of P.anserina and E.nutans.In addition,grazing decreased the values of net photosynthetic rate-photosynthetically active radiation(PN-PAR)curve parameters,such as light-saturated net photosynthetic rate,apparent quantum efficiency,light compensation point,light saturation point,and dark respiration rate.Our results demonstrated that grazing was the primary limiting factor for photosynthesis of dominant grassland species in the study area.

Modified non-rectangular hyperbola equation with plant height for photosynthetic light-response curves of Potentilla anserina and Elymus nutans at various growth phases in the Heihe River Basin, Northwest China

The non-rectangular hyperbola(NRH)equation is the most popular method that plots the photosynthetic light-response(PLR)curve and helps to identify plant photosynthetic capability.However,the PLR curve can't be plotted well by the NRH equation at different plant growth phases due to the variations of plant development.Recently,plant physiological parameters have been considered into the NRH equation to establish the modified NRH equation,but plant height(H),an important parameter in plant growth phases,is not taken into account.In this study,H was incorporated into the NRH equation to establish the modified NRH equation,which could be used to estimate photosynthetic capability of herbage at different growth phases.To explore photosynthetic capability of herbage,we selected the dominant herbage species Potentilla anserina L.and Elymus nutans Griseb.in the Heihe River Basin,Northwest China as the research materials.Totally,twenty-four PLR curves and H at different growth phases were measured during the growing season in 2016.Results showed that the maximum net photosynthetic rate and the initial slope of PLR curve linearly increased with H.The modified NRH equation,which is established by introducing H and an H-based adjustment factor into the NRH equation,described better the PLR curves of P.anserina and E.nutans than the original ones.The results may provide an effective method to estimate the net primary productivity of grasslands in the study area.

Identification of α-glucosidase inhibitors from Clinacanthus nutans leaf extract using liquid chromatography-mass spectrometry-based metabolomics and protein-ligand interaction with molecular docking

The present study used in vitro and in silico techniques, as well as the metabolomics approach to characterise α-glucosidase inhibitors from different fractions of Clinacanthus nutans. C. nutans is a medicinal plant belonging to the Acanthaceae family, and is traditionally used to treat diabetes in Malaysia. nHexane, n-hexane: ethyl acetate(1:1, v/v), ethyl acetate, ethyl acetate: methanol(1:1, v/v), and methanol fractions were obtained via partitioning of the 80% methanolic crude extract. The in vitro α-glucosidase inhibitory activity was analyzed using all the fractions collected, followed by profiling of the metabolites using liquid chromatography combined with mass spectrometry. The partial least square(PLS) statistical model was developed using the SIMCA P^+14.0 software and the following four inhibitors were obtained:(1) 4,6,8-Megastigmatrien-3-one;(2) N-Isobutyl-2-nonen-6,8-diynamide;(3) 1′,2′-bis(acetyloxy)-3′,4′-didehydro-2′-hydro-β, ψ-carotene; and(4) 22-acetate-3-hydroxy-21-(6-methyl-2,4-octadienoate)-olean-12-en-28-oic acid. The in silico study performed via molecular docking with the crystal structure of yeast isomaltase(PDB code: 3 A4 A) involved a hydrogen bond and some hydrophobic interactions between the inhibitors and protein. The residues that interacted include ASN259, HID295, LYS156, ARG335,and GLY209 with a hydrogen bond, while TRP15, TYR158, VAL232, HIE280, ALA292, PRO312, LEU313,VAL313, PHE314, ARG315, TYR316, VAL319, and TRP343 with other forms of bonding.

Adventitious rhizogenesis in Bambusa nutans and Bambusa tulda: Influence of seasonal variation, IBA and cutting type

The influence of seasonal variation, indole-3-butyric acid （IBA） and type of cuttings was examined on induction and growth of adventitious roots in Bambusa nutans Wall. and Bambusa tulda Roxb. Singlenode culm and culm-branch cuttings from the mature culms were provided with immersion treatment for 24 h of either water （control） or 2 mM IBA in four different seasons, i.e., spring （mid February）, summer （mid May）, rainy （mid July）, and winter （mid November） and maintained for two months in the mist chamber at the relative humidity of （70±5）% and the tenlperature of （30±2）℃. In B. nutans, adventitious rooting occttrred in both types of cuttings in all the seasons with the best rooting in the summer season i.e., May （88% in culm cuttings） and the least in winter. On the contrary, adventitious rooting was recorded only in culm cuttings in spring and summer season in B. tulda. IBA treatment significantly enhanced rooting, root number and root length; registering 14 to 17 times improvement over control in the best rooting season. Three factor- interactions （season × cutting type × IBA treatment） were significant for rooting in B. nutans and all characteristics, except sprouting in B, tulda. Thus, single-node culm and culm-branch cuttings in B. nutans and culm cuttings in B. tulda treated with 2 mM IBA during spring （February） to summer （May） season are recommended for their clonal multiplication.

Biochemical changes associated with flowering in Bambusa arundinacea and Bambusa nutans

Biochemical changes associated with flowering in Bambusa arundinacea Linn and Bambusa nutans Wall.ex Munro were analyzed.Gregarious flowering was initiated in natural areas and plantations of B.arundinacea in late 2014 and reached full bloom in early 2015,whereas sporadic flowering recorded during 2014–2015 in vegetatively propagated plants of B.nutans.Leaf and nodal shoot samples from flowering culms/shoots and nonflowering culms/shoots were collected in February 2015 at the initiation of fruit filling,then analyzed and compared for soluble sugars,phenols and peroxidase activity.In both species sugars were higher in leaves of flowering culms/shoots and lower in nodal shoots of flowering culms/shoots compared to the nonflowering.Phenols were lower in leaves and nodal shoots of flowering B.arundinacea,but higher in leaves and decreases in nodal shoots of B.nutans.Peroxidase activity increases in leaves and nodal shoots of B.arundinacea after flowering but increases in nodal shoots and decreases in leaves of B.nutans.

Molecular cytogenetic study on the plants of Elymus nutans with varying fertility on the Qinghai-Tibet Plateau

A molecular cytogenetic investigation was conducted on plants of the allohexaploid species Elymus nutans with varying fertility on the Qinghai-Tibet Plateau.Molecular karyotyping revealed that chromosome variants were distributed unevenly among genomes and among different homologue chromosomes in each genome.The plants with varying fertility exhibited significantly higher numbers of chromosome variants than did the normal fertility samples,although both kinds of plants showed the same pattern of high-to-low polymorphism from the Y to St and H genomes.Heterozygosis and karyotype heterozygosity in the plants with varying fertility were 3-and 13-fold higher than those in normal samples,respectively.Significant negative correlations were found not only between seed setting rates and total genome heterozygosity but also between seed setting rates and heterozygosity of each genome in the plants of varying fertility.Chromosome pairing analysis was performed using genomic in situ hybridization in selected plants of different fertility levels.The pairing of chromosomes at meiotic metaphase I was mostly bivalent,although univalent,trivalent,quadrivalent,and other polyvalents also occurred;in addition,chromosome configuration forms and frequencies varied among the studied samples.ANOVA results showed that the average number of ring bivalents in the Y genome was significantly higher than those in the St and H genomes.Significant positive correlations between pollen grain fertility and ring bivalent number were found in the St and H genomes but not in the Y genome.Furthermore,chromosome configuration parameters(total bivalents,numbers of ring and rod bivalents)were found to be significantly correlated with heterozygosity and seed setting rates in the St and H genomes,respectively,but not in the Y genome.It was inferred that the seed setting rate and pollen grain fertility in E.nutans are strongly influenced by the heterozygosity of each genome,but the Y genome differs from the St and H genomes due to chromosome pair alterations.The St and H genomes may contain more chromosome structural variations than the Y genome in E.nutans.

Effects of Altitude Change on Nutritional Quality and Elymus nutans Regularity in Qinghai-Tibet Plateau

In order to reveal the effects of different altitudes on the nutritional quality of wild forage in Qinghai-Tibet Plateau,this study used Elymus nutans as the tested plants to evaluate the changes of nutrient contents and the correlation between the nutrient contents and altitudes.Four sampling sites were set up at altitudes of 2562,2660,2775 and 2905 m with the vertical distance among each sampling point was about 100 m.The results showed that the crude protein,ash and phosphorus contents of Elymus nutans decreased significantly with an increase in altitudes.The crude protein contents decreased by 1.87%with each 100 m increase in altitudes.The variation rule of crude protein contents with altitudes in the simulated curve was"y=-0.0187x+63.244(R^(2)=0.9557)".The crude ash contents decreased by 1.77%with each 100 m increase in altitudes.The variation rule of crude ash contents with altitudes in the simulated curve was"y=-0.0177x+56.144(R^(2)=0.978)".Neutral detergent fiber(NDF)and acid detergent fiber(ADF)showed an overall increasing trend with the increase of altitudes,but the most obvious increase was at 2775 m.The contents of crude fat and Ca did not change regularly with altitudes.

Effects of Ethanol Extract of Clinacanthus nutans on Gut Microbiota and Lipid Metabolism of HFD-induced Obese Mice

[Objectives]To explore the effects of ethanol extract of Clinacanthus nutans on gut microbiota and lipid metabolism in high-fat diet(HFD)-induced obese mice.[Methods]A HFD-induced obesity mouse model was established,and the mice were randomly divided into high-fat model group,high-dose and low-dose groups of ethanol extract of C.nutans.Normal group and high-fat model group were given normal saline by intragastric administration every day.The high-dose and low-dose groups of the ethanol extract of C.nutans were given corresponding drugs by intragastric administration.After 8 weeks of administration,the body weight,fat accumulation,blood lipid level,and liver histopathological changes of the mice in each group were compared.The high-throughput sequencing of 16S rRNA was used to sequence the fecal samples of mice in each group,and the effects of ethanol extract of C.nutans on lipid metabolism and gut microbiota structure in HFD-induced obese mice were analyzed.[Results]Compared with the normal group,the high-fat model group had significantly higher body weight(P<0.01),increased subcutaneous fat accumulation(P<0.01),increased liver fat content,and increased serum TC,TG and LDL levels(P<0.01).Compared with the high-fat model group,the high-dose group of the ethanol extract of C.nutans significantly reduced the body weight of obese mice(P<0.01),reduced the subcutaneous fat accumulation in obese mice(P<0.05),inhibited the synthesis of fat in the liver,significantly reduced serum TC,TG levels(P<0.01),and significantly increased serum HDL levels(P<0.01).Compared with the normal group,the relative abundance of Firmicutes and Proteobacteria in the gut microbiota of mice in the high-fat model group was significantly increased,while the relative abundances of Bacteroidetes,Verrucomicrobia,and Akkermansia were significantly decreased(P<0.01),and the ratio of Firmicutes to Bacteroidetes was significantly increased.After treatment with ethanol extract of C.nutans,the ratio of Firmicutes to Bacteroidetes was reduced,the relative abundance of Bacteroidetes,Verrucomicrobia and Akkermansia(AKK)increased(P<0.05),while the relative abundance of Firmicutes and Proteobacteria decreased(P<0.05).[Conclusions]HFD-induced obese mice have imbalanced gut microbiota structure and abnormal lipid metabolism,and the ethanol extract of C.nutans can improve the imbalance of microbiota structure and lipid metabolism in obese mice.

Geographical Traceability of Clinacanthus nutans with Near-Infrared Pectroscopy and Chemometrics

In this study, a seed origin discrimination model for Clinacanthus nutans was developed. First, 81 C. nutans samples from three seed origin locations were collected, and their Near-Infrared (NIR) spectra were obtained. Next, Principal Component Analysis (PCA) was performed on the NIR spectra of the 81 C. nutans samples. Then, MSC (multiplicative scatter correction), SNV (standard normal variate), first derivative, and second derivative pre-treatments of the C. nutans spectra were performed and combined with the Support Vector Machine (SVM) algorithm for modelling and analysis. Among these methods, first-order derivative pre-treatment achieved the best SVM model effectiveness, with a training set accuracy of 93.44% (57/61) and a test set accuracy of 85.00% (17/20). In order to further improve the discrimination accuracy of the model, three optimization algorithms Grid Search (GS), Genetic Algorithm (GA), and Particle Swarm Optimization (PSO) were employed to identify the best c and g parameters for the SVM model. The results demonstrated that the PSO optimization algorithm yielded the best parameters of c = 0.8343, g = 57.8741, with corresponding model training set the accuracy of 96.36% (60/61) and test set the accuracy of 95.00% (20/21). Therefore, developing a seed origin classification model for C. nutans based on NIR spectroscopy combined with chemometrics is feasible and has the advantages of being simple, rapid, and green.

Phylogenetic analysis and in vitro culture of mosses fromthe Antarctic Fildes Peninsula

Molecular genetic techniques have proven very useful for initial analysis of the extent of genetic variation and dispersal in several Antarctic moss species. In the present study, the small subunit ribosomal RNA （SSU rDNA） and internal transcribed spacers of the nuclear ribosomal DNA （ITS rDNA） were sequenced in nine individuals of different mosses from the Fildes Peninsula of Antarctica. Sequence alignment showed that the extreme environment tended to increase the genetic diversity of Antarctic mosses. In addition, in our phylogenetic analysis, one previously unidentified Antarctic moss species was characterized by comparison with SSU and ITS rDNA sequences of known moss species. Moreover, the optimal culture medium and conditions for surface explant sterilization and protonemata induction in tissue culture of Pohlia nutans were investigated. The successful establishment of a tissue culture protocol together with the phylogenetic analysis of Antarctic mosses will provide technological support to establish an effective resource regeneration method for discovering new functional genes and gaining novel insights into the mechanisms of stress acclimation.

忧遁草抗氧化活性评价和总黄酮、总多酚含量测定

忧遁草富含黄酮类、多酚类、甾醇类、三萜类、生物碱类和糖苷类等化合物,具有清热解毒、利尿消肿和祛湿等功效。为了进一步探究忧遁草的有效活性部位,本研究对其根、茎、叶三个部位进行了清除ABTS和DPPH自由基的能力测定,建立TBHP诱导HepG2细胞氧化损伤模型,采用三氯化铝和福林酚比色法测定忧遁草不同部位的粗提物中总黄酮和总多酚的含量。结果表明,忧遁草对ABTS和DPPH自由基有一定的清除作用,根、茎、叶提取物对清除ABTS和DPPH自由基的IC50分别为:(0.68±0.074)mg/mL、(1.34±0.108)mg/mL、(0.41±0.006)mg/mL和(0.46±0.013)mg/mL、(0.644±0.016)mg/mL、(0.408±0.018)mg/mL,其作用效果叶>根>茎。忧遁草根、茎、叶提取物对HepG2细胞的氧化损伤也有一定的保护作用,且作用效果均为叶>根>茎,叶片提取物浓度为10μg/mL时,可将细胞存活率由(45.18±2.429)%提高至(78.07±3.188)%。忧遁草不同部位的总黄酮和总多酚含量分别在(3.01±0.055)%^(5.43±0.072)%和(0.74±0.043)%^(1.42±0.124)%之间,其中叶片中黄酮和多酚含量最高。忧遁草的抗氧化活性和总黄酮、多酚含量存在相关性。忧遁草提取物具有良好的抗氧化效果,尤其是叶提取物,具有较高的开发利用价值,有望开发成为新型食品添加剂或抗氧化剂。

Photosynthetic and Respiratory Acclimation to Experimental Warming for Four SpeCies in a Tallgrass Prairie Ecosystem

Global temperature has been Increased by 0.6 ℃ over the past century and is predicted to Increase by 1.4-5.8 ℃ by the end of this century. It is unclear what impacts global warming will have on tallgrass species. In the present study, we examined leaf net photosynthetic rate （P.） and leaf respiration rate in darkness （Rd） of Aster erlcoldes （L.） Nesom, Ambrosia psllostachya DC., Helianthus mollis Lam., and Sorghastrum nutans （L.） Nash In response to experimental warming in a tallgrass prairie ecosystem of the Great Plains, USA, in the autumn （fall） of 2000 and through 2001. Warming has been Implemented with infrared heaters since 21 November 1999. The P. increased significantly In spring, decreased in early fall, and did not change in summer and late fall in the four species under warming compared with control. The Rd of the four species increased significantly until mid-summer and then did not change under warming. Measured temperature-response curves of P. showed that warming Increased the optimum temperature of P. （Topt） by 2.32 and 4.59 ℃ for H. mollis and S. nutans, respectively, in August, whereas there were no changes in May and September, and A. ericoldes and A. psllostachya also showed no changes in any of the 3 months. However, P. at optimum temperature （Popt） showed downregulation in September and no regulation in May and August for all four species. The temperature-response curves of Rd Illustrate that the temperature sensitivity of Rd, Q10, was lower in the warmed plots compared with the control plots, except for A. ericoides in August, whereas there were no changes In May and September for all four species. The results of the present study indicate that photosynthetic and respiratory acclimation varies with species and among seasons, occurring In the mid-growing season and not in the early and late growing seasons.

Arbuscular mycorrhizal fungi in the rhizosphere soil of poisonous plants depressed the growth of pasture grasses in the Tibetan Plateau Alpine meadow

In order to explore the influence of arbuscular mycorrhizal(AM)fungi in the rhizosphere of poisonous plants on the neighboring pasture grasses in the Tibetan Plateau Alpine meadow ecosystem,rhizosphere soils were collected from eight different poisonous plants in degraded grasslands and one from pasture grass in non-degraded grasslands(CK).The collected soils were used as inocula to assess the influence of indigenous AM fungi on the growth of two typical pasture grass species,Elymus nutans and Poa pratensis,in a bioassay experiment.Five growth parameters and two AM parameters were determined.The mycorrhizal responsiveness and the importance value were calculated.Significant differences between the eight poisonous plants and CK were observed.Compared to CK,rhizosphere soil from the eight poisonous plants had lower AM fungal spore densities.The growth of E.nutans and P.pratensis seedlings was depressed with the inoculation from poisonous plants rhizosphere soil.This study demonstrated that the presence of poisonous plants with grassland degradation altered inherent AM fungal community abundance,and could exert inhibition effects on the growth of pasture grasses.It may attribute to discover the important role of rhizosphere soil of different poisonous plants to AM fungal community on the Alpine meadow.