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天然产物的质谱智能解析研究
No full text串联质谱在鉴定天然产物的分子结构方面起着重要的作用.每一类天然产物,在串联质谱中除有常规的质谱裂解方式外,通常还具有因特定骨架类型而产生的特征裂解.因此可以通过天然产物各类成分的特征质谱裂解所产生的特征碎片离子(diagnostic ions)来确认该类天然产物的结构类型,然后再由常规的裂解方式来推测其周边可能的取代基团.基于以上思路,我们设计并构建了一种天然产物质谱智能解析软件SmartMass
Effect of microtopography on soil respiration in an alpine meadow of the Qinghai-Tibetan plateau
No full textSoil respiration is an important component of terrestrial carbon cycling and is sensitive to environmental change. Most previous studies focus on the effect of soil temperature and moisture on soil respiration, whereas the impact of spatial heterogeneity (e.g., microtopography) is seldom studied. To test the impact of microtopography on soil respiration, we performed a field investigation to examine soil respiration, soil temperature, soil water content, soil total porosity, soil organic content, and plant biomass at a hummock site (composed of grass hummocks and inter-hummock areas) and an adjacent flat meadow of the Qinghai-Tibetan plateau. Similar seasonal dynamics of soil respiration in the grass hummocks, inter-hummock areas, and flat meadow were found in the alpine meadow of the Qinghai-Tibetan plateau. However, soil respiration of the grass hummocks was 79.3% and 413.9% higher than that of the flat meadow during the growing (April, June, August) and non-growing seasons (October, December, February), respectively. Although there was no difference in soil respiration between the inter-hummock areas and the flat meadow during the non-growing season, soil respiration was 42.5% higher at the inter-hummock areas than the flat meadow during growing season. Larger soil porosity, greater surface area, and more substrate supply, but not more root growth, likely contributed to the higher soil respiration of grass hummocks. Our findings suggest that the impact of spatial heterogeneity on soil respiration should be taken into consideration to facilitate the accurate estimation of soil carbon fluxes at ecosystem and regional scales
The effect of water table decline on soil CO2 emission of Zoige peatland on eastern Tibetan Plateau: A four-year in situ experimental drainage
No full textWater table decline is a major threat to soil organic carbon in peatlands worldwide principally because it may largely increase soil CO2 emission (SCE). This study is to determine the response of SCE to water table decline in the Zoige peatland of Tibetan Plateau, which has experienced rapid decline of water table due to climate change and anthropogenic drainage. We conducted a field in situ drainage experiment consisting of low (plots surrounded by 50 cm deep ditches), intermediate (20 cm deep) and high (intact) water table levels. The experiment lasted for about four years, during which we measured SCE rate and associated variables including soil temperature and moisture with a higher frequency in the growing season (May-September) than the non-growing season (October-April). Experimental drainage decreased water table height by ca. 12 cm and 15 cm (relative to the intact) and soil moisture (at 5 cm soil) by 6% and 12% (relative to 45% in the intact) on average in intermediate and low water table treatments, respectively, but it did not affect soil temperature during the experimental years. The effect of drainage on SCE varied with season. In the non-growing season, the drainage effect was nonsignificant in each measurement possibly because the low-temperature effect overrode the drainage effect on SCE. In the growing season, the drainage mostly increased the emission except for several cases, in which a negative effect was observed. The negative effect of drainage could be due to the low soil moisture (< 25%) in the drained treatments. Provided that the magnitude and the duration of the SCE increase were greater than those of the decrease, it can be estimated that drainage increased SCE by 17% and 20% on average in the low and the intermediate water table treatments, respectively, over the experimental years. Our results suggest that water table decline may facilitate net carbon emission and hence decrease soil carbon storage in the Zoige peatland. We call for artificial filling of the ditches that were historically created by both human beings and storm waters to increase water table in the Zoige peatland
A plastid phylogeny and character evolution of the Old World fern genus Pyrrosia (Polypodiaceae) with the description of a new genus: Hovenkampia (Polypodiaceae)
No full textThe Old World fern genus Pyrrosia (Polypodiaceae) offers a rare system in ferns to study morphological evolution because almost all species of this genus are well studied for their morphology, anatomy, and spore features, and various hypotheses have been proposed in terms of the phylogeny and evolution in this genus. However, the molecular phylogeny of the genus lags behind. The monophyly of the genus has been uncertain and a modern phylogenetic study of the genus based on molecular data has been lacking. In the present study, DNA sequences of five plastid markers of 220 accessions of Polypodiaceae representing two species of Drymoglossum, 14 species of Platycerium, 50 species of Pyrrosia, and the only species of Saxiglossum (subfamily Platycerioideae), and 12 species of other Polypodiaceae representing the remaining four subfamilies are used to infer a phylogeny of the genus. Major results and conclusions of this study include: (1) Pyrrosia as currently circumscribed is paraphyletic in relation to Platycerium and can be divided into two genera: Pyrrosia s.s. and Hovenkampia (gen. nov.), with Hovenkampia and Platycerium forming a strongly supported Glade sister to Pyrrosia s.s.; (2) Subfamily Platycerioideae should contain three genera only, Hovenkampia, Platycerium, and Pyrrosia s.s.; (3) Based on the molecular phylogeny, macromorphology, anatomical features, and spore morphology, four major clades in the genus are identified and three of the four are further resolved into four, four, and six subclades, respectively; (4) Three species, P. angustissima, P. foveolata, and P. mannii, not assigned to any groups by Hovenkamp (1986) because of their unusual morphology, each form monospecific clades; (5) Drymoglossum is not monophyletic and those species previously assigned to this genus are resolved in two different subclades; (6) Saxiglossum is resolved as the first lineage in the Niphopsis Glade; and (7) The evolution of ten major morphological characters in the subfamily is inferred based on the phylogeny and various morphological synapomorphies for various clades and subclades are identified. (C) 2017 Elsevier Inc. All rights reserved
Effects of canopy gaps on N2O fluxes in a tropical montane rainforest in Hainan of China
No full textBackground and aims: Tropical montane rainforests play an important role in increasing atmospheric N2O concentration. Although accurate estimations of N2O fluxes in tropical montane rainforests are critical for predicting global climate change, there are still considerable uncertainties about the spatial and temporal variability of the emissions. This study aims to investigate the effects of canopy gap caused by typhoons on N2O emissions, a key factor for understanding the spatial heterogeneity and supporting environmental regulations. Methods: N2O fluxes were measured monthly using static chambers both inside and outside two large canopy gaps in the tropical montane rainforest of the Jianfengling National Natural Reserve on Hainan Island, south of China, from August 2012 to July 2013. Results: Mean annual N2O emissions were 2.19 +/- 0.43 kg N2O-N ha(-1) yr(-1) inside canopy gaps, and 1.19 +/- 0.29 kg N2O-N ha(-1) yr(-1) outside canopy gaps, revealing substantial differences in N2O emissions resulting from forest structure. Moreover, N2O emission rates within canopy gaps during the wet season (2.89 kg N2O-N ha(-1) yr(-1)) were significantly higher than those during the dry season (1.34 kg N2O-N ha(-1) yr(-1)), suggesting strong regulation of soil moisture and precipitation in controlling soil N dynamics. However, there were significant nonlinear relationships between N2O fluxes and water filled pore space, and soil temperature within canopy gaps, but no significant relationships were found under the closed canopy. Conclusions: Contribution of canopy gaps should be considered to avoid underestimation of N2O emission rates from disturbed forests. Interestingly, emissions from gaps are more strongly coupled with climate drivers (moisture and temperature), with important implications for climate change projections. Therefore, the further research is needed to study the biogeochemical processes and mechanisms behind such phenomenon. (C) 2017 Elsevier B.V. All rights reserved
The demographic response of a deciduous shrub (the Indigofera bungeana complex, Fabaceae) to the Pleistocene climate changes in East Asia
No full textEast Asia harbors the highest level of floristic diversity among the world's temperate regions. Despite the increase in phylogeographic studies of temperate plants in East Asia, far less attention has been paid to widely distributed deciduous shrubs that widespread across several floral regions. We sequenced two chloroplast DNA (cpDNA) fragments (ndhJ-trnF and trnD-trnT) and one nuclear DNA (Pgk1) of 472 individuals from 51 populations of such a group, the Indigofera bungeana complex. We used population genetic data as well as ecological niche modelling to examine the evolutionary history and glacial refugia during the Last Glacial Maximum (LGM) of this group. We recovered 133 cpDNA and 68 nuclear haplotypes. The star-phylogeny of the recovered cpDNA and nuclear haplotypes and demographic analyses suggested distinct range expansion of I. bungeana complex have occurred during the early and middle Pleistocene. The climate change of the LGM might have affected little on the distribution of this complex based on the niche modelling. However, these climate changes and geographic isolation probably resulted in fixtures of the private haplotypes and genetic differentiations between regions. Our results suggested that this arid-tolerant species complex may have different responses to the Quaternary climate changes with those climate-sensitive species
Dendrolycopodium verticale comb. nov (Lycopodiopsida: Lycopodiaceae) from China
No full textA new combination in the lycophyte genus Dendrolycopodium (Lycopodiacae) from Lycopodium, D. verticale (Li Bing Zhang) Li Bing Zhang & X. M. Zhou, for a Chinese species is made
A systematic review on ethnomedicines of anticancer plants
No full textCancer is a serious health problem and the second leading cause of death around the globe. Present review is an attempt to provide utmost information based on ethno-pharmacological and toxicological aspects of anti-cancer plants of the world. A total of 276 articles published in English journals and containing maximum ethnomedicinal information were reviewed using several data sources such as; Google scholar, Web of Science, Scopus, PubMed and floras of different countries. A total of 199 anti-cancer plants were recorded in present review and results indicated that traditional medicines are mostly being use in developing countries for cancer treatment. Traditionally and scientifically skin and breast cancer types gained more focus. Seventy plants were reportedly analyzed for in-vitro activities while 32 plants were having in-vivo reports. Twenty nine pure compounds (mostly phenolic) were reportedly isolated from anti-cancer plants and tested against different cancer cell lines. Inspite having better efficiency of ethnomedicines as compared to synthetic drugs, several plants have also shown toxic effects on living system. Therefore, we invite researchers attention to carry out detailed ethno-pharmacological and toxicological studies on un-explored anti-cancer plants in order to provide reliable knowledge to the patients and develop novel anti-cancer drugs. Copyright (C) 2017 John Wiley & Sons, Ltd
Polystichum duyunense (subg. Haplopolystichum; Dryopteridaceae), a new cave fern from Guizhou, China
No full textA new cave fern of Polystichum (subg. Haplopolystichum; Dryopteridaceae), P. duyunense, is described from a limestone cave in southern Guizhou, China. Polystichum duyunense is most similar to P. cavernicola in having oblong pinnae, but the former has pinnae larger, often angled basiscopically, and somewhat imbricate, while the latter has pinnae smaller, angled acroscopically, and apart from each other
ITS non-concerted evolution and rampant hybridization in the legume genus Lespedeza (Fabaceae)
No full textThe internal transcribed spacer (ITS) as one part of nuclear ribosomal DNA is one of the most extensively sequenced molecular markers in plant systematics. The ITS repeats generally exhibit high-level within-individual homogeneity, while relatively small-scale polymorphism of ITS copies within individuals has often been reported in literature. Here, we identified large-scale polymorphism of ITS copies within individuals in the legume genus Lespedeza (Fabaceae). Divergent paralogs of ITS sequences, including putative pseudogenes, recombinants, and multiple functional ITS copies were sometimes detected in the same individual. Thirty-seven ITS pseudogenes could be easily detected according to nucleotide changes in conserved 5.8S motives, the significantly lower GC contents in at least one of three regions, and the lost ability of 5.8S rDNA sequence to fold into a conserved secondary structure. The distribution patterns of the putative functional clones were highly different between the traditionally recognized two subgenera, suggesting different rates of concerted evolution in two subgenera which could be attributable to their different extents/frequencies of hybridization, confirmed by our analysis of the single-copy nuclear gene PGK. These findings have significant implications in using ITS marker for reconstructing phylogeny and studying hybridization