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Using anatomical traits to understand root functions across root orders of herbaceous species in a temperate steppe
No full textRoot anatomical traits play crucial roles in understanding root functions and root form-function linkages. However, the root anatomy and form-function linkages of monocotyledonous and dicotyledonous herbs remain largely unknown. We measured order-based anatomical traits and mycorrhizal colonization rates of 32 perennial herbs of monocotyledons and dicotyledons in a temperate steppe. For monocots, relative constant proportion of cortex and mycorrhizal colonization rates, but increased cell-wall thickening of the endodermis and proportion of stele were observed across root orders, indicating a slight reduction in absorption capacity and improvement in transportation capacity across orders. For dicots, the cortex and mycorrhizal colonization disappeared in the fourth-order and/or fifth-order roots, whereas the secondary vascular tissue increased markedly, suggesting significant transition of root functions from absorption to transportation across root orders. The allometric relationships between stele and cortex differed across root orders and plant groups, suggesting different strategies to coordinate the absorption and transportation functions among plant groups. In summary, our results revealed different functional transition patterns across root orders and distinct strategies for coordinating the absorption and transportation of root system between monocots and dicots. These findings will contribute to our understanding of the root form and functions in herbaceous species
From canopy complementarity to asymmetric competition: The negative relationship between structural diversity and productivity during succession
No full textPositive relationships between structural diversity and forest productivity have been documented in controlled experiments and early secondary forests, however, negative relationships have also been observed in late successional forests. The mechanisms causing observed relationships between structural diversity and productivity are not well-established, but complementarity among crowns and asymmetric competition have been suggested. We used LiDAR and repeated census data to examine the relationship between canopy structural diversity and productivity in nine 1-ha subtropical forest plots along a disturbance gradient in southeastern China. We quantified the relative importance of community composition, species diversity, canopy structural diversity, leaf area index (LAI) and disturbance regime on productivity using piecewise structural equation modelling. We also tested how vertical leaf area distribution affected productivity. Contrary to many prior observations, we found a negative relationship between canopy structural diversity and forest productivity. The negative effect may stem from asymmetric competition between overstorey and understorey leaves, leading to a lower leaf area efficiency (i.e. wood production per leaf area). Asymmetric competition was suggested by a negative relationship between understorey leaf area and total productivity. Changes in community composition over the disturbance gradient, but not species diversity, had a significant effect on productivity. Synthesis. Our study suggests that leaf area and canopy structural diversity have contrasting effects on productivity in this subtropical forest, and this needs to be considered when estimating rates of carbon sequestration in secondary forests. The negative effect of asymmetric competition on productivity is comparable to that of the shift in species composition over succession, highlighting the role of canopy structural diversity in shaping forest productivity
Spores morphology of the family Pteridaceae from Shandong Province, China
No full textIn this article, we explored systematically the spore morphology of Pteridaceae by observation of the species distributed in Shandong Province using scanning electron microscopy (SEM). The results showed that the spore morphology of all the species in the family is tetrahedral and trilete. The characters of spore ornamentation are intraspecies stable, but significantly different among species and genera. Spore morphology is significant in exploring the phylogenetic relationships of Pteridaceae as well as in generic and specific delimitations
Presence of cryptic species in host insects forms a hierarchical Wolbachia infection pattern
No full textAlthough Wolbachia spp. are described as one of the most prevalent groups of endosymbiotic intracellular bacteria in invertebrates, studies often found large variations in Wolbachia infection rate at the species level. The underlying mechanisms of these variations however remain unclear. Given some phenotypic effects of Wolbachia such as cytoplasmic incompatibility and difficulties to be transmitted among host populations with deep genetic divergence, we hypothesized that cryptic species could play an important role in the spreading success of Wolbachia. Here we used Wiebesia pumilae, the morphospecies specifically pollinating Ficus pumila to test our hypothesis. We collected individuals from 40 locations covering most of its distribution range in China. Using a mtDNA gene, we suggested a total of three cryptic species in W. pumilae with a parapatric distribution pattern. At the morphospecies level, we detected an overall Wolbachia infection rate of 52.8%. In contrast, at the cryptic species level, we found that all infected individuals belonged to only one cryptic species. These results support our hypothesis and indicate that cryptic species boundaries can create a hierarchical Wolbachia infection pattern and the potential role of Wolbachia infection in restricting gene flow among cryptic species
Germination characteristics of three key species and their implications for vegetation restoration in northern China
No full textSeed germination is a complex physiological process that can affect species establishment as well as vegetation restoration and dynamics; however, the germination characteristics of several key species used to combat desertification remain unclear. In light, temperature, and air humidity-controlled growth chambers, four different light treatments, five alternative temperature treatments, 11 levels of water potential, and five constant temperatures were set up to study the effects of light, temperature, and water stress on the completion of germination of Medicago sativa L, Astragalus adsurgens Pall., and Glycyrrhiza uralensis Fisch. The results showed that completion of germination of G. uralensis seeds occurred significantly less than that of M. sativa and A. adsurgens. Light intensity had no significant effect on the final germination percentage of M. sativa, A. adsurgens, and G. uralensis, but the germination rate under 100 and 400 mu mol.m(-2).s(-1) light was significantly greater than that under 25 mu mol.m(-2).s(-1). Temperature had no significant effect on the final germination percentage of these species' seeds, and the germination rate was greater at 15/25 degrees C and 20/30 degrees C. The germination rate decreased as the water potential decreased. The germination results indicate that late spring is a suitable sowing time for G. uralensis to obtain optimal levels of completion of germination
Deepened snow cover mitigates soil carbon loss from intensive land-use in a semi-arid temperate grassland
No full text1. Carbon (C) loss due to soil erosion is a major issue in semi-arid grasslands. The extent of soil erosion is determined by soil properties and vegetation structure, especially during the non-growing season. In many Inner Mongolian grasslands, intensive land-use, such as overgrazing and mowing, has severely reduced plant cover and damaged soil structure, which has exacerbated soil C loss by erosion. At the same time, increasing winter snowfall due to climate change is stimulating plant growth and altering plant composition. However, we do not know how changes in winter snow cover interact with land-use practices to regulate soil C loss due to erosion. 2. Here, we conducted a 6-year snow manipulation experiment under different land-use practices (control; moderately mowed, MM; heavily mowed, HM) to measure net changes in soil depth, soil C, plant biomass and vegetation structure. 3. After 6 years, soil C loss under ambient snow was three times greater in the MM and four times greater in the HM treatment compared with controls during non-growing season. However, deepened winter snow alleviated erosion-induced soil C loss by 14%, 47%, 16% in the controls, MM and HM treatments respectively. 4. The severity of soil C loss declined with increasing above-ground biomass (AGB), surface root biomass and vegetation structure. Vegetation structure and AGB explained more of the variation in soil C loss than surface root biomass, possibly because a complex canopy and plant cover increases overall surface roughness, thereby reducing soil C loss. Intensified land-use reduced AGB, surface root biomass and vegetation structure, but deepened snow increased overall surface roughness by promoting AGB. Hence, our study demonstrates that deepened snow can alleviate soil C loss due to land-use practices by promoting AGB. A free Plain Language Summary can be found within the Supporting Information of this article
A chromosome-level genome of Syringa oblata provides new insights into chromosome formation in Oleaceae and evolutionary history of lilacs
No full textLilacs (Syringa L.), a group of well-known ornamental and aromatic woody plants, have long been used for gardening, essential oils and medicine purposes in East Asia and Europe. The lack of knowledge about the complete genome of Syringa not only hampers effort to better understand its evolutionary history, but also prevents genome-based functional gene mining that can help in the variety improvement and medicine development. Here, a chromosome-level genome of Syringa oblata is presented, which has a size of 1.12 Gb including 53 944 protein coding genes. Synteny analysis revealed that a recent duplication event and parallel evolution of two subgenomes formed the current karyotype. Evolutionary analysis, transcriptomics and metabolic profiling showed that segment and tandem duplications contributed to scent formation in the woody aromatic species. Moreover, phylogenetic analysis indicated that S. oblata shared a common ancestor with Osmanthus fragrans and Olea europaea approximately 27.61 million years ago (Mya). Biogeographic reconstruction based on a resequenced data set of 26 species suggested that Syringa originated in the northern part of East Asia during the Miocene (approximately 14.73 Mya) and that the five Syringa groups initially formed before the Late Miocene (approximately 9.97 Mya). Furthermore, multidirectional dispersals accompanied by gene introgression among Syringa species from Northern China during the Miocene were detected by biogeographic reconstruction. Taken together, the results showed that complex gene introgression, which occurred during speciation history, greatly contributed to Syringa diversity
Non-linear modelling reveals a predominant moisture limit on juniper growth across the southern Tibetan Plateau
No full textBackground and Aims Tree growth in plateau forests is critically limited by harsh climatic conditions. Many mathematical statistical methods have been used to identify the relationships between tree growth and climatic factors, but there is still uncertainty regarding the relative importance of these factors across different regions. We tested major climatic limits at 30 sites to provide insights into the main climatic limits for juniper trees (Juniperus tibetica Kom.) across the southern Tibetan Plateau. Methods We analysed the linear and non-linear relationships between tree growth and climatic factors using Pearson correlation statistics and a process-based forward Vaganov-Shashkin-Lite (VS-Lite) model, respectively. These relationships were used to identify the strength of the influence of different climatic factors throughout the species' growing season and to identify the main climatic factors limiting tree growth. Key Results Growth of juniper trees began in April and ended in October in the study area. The radial growth of juniper trees was limited by soil moisture throughout the summer (June-August) of the current year at 24 sampling sites and was limited by temperature at the other six sites on the southern Tibetan Plateau. Conclusions Soil moisture limited juniper growth at the majority of sites. Temperature in the current summer limited the growth of juniper trees at a few sampling sites in the western part of the study area. Local climate conditions may contribute to different limiting factors in the growth response of trees on the southern Tibetan Plateau. These findings may contribute to our understanding of divergent forest dynamics and to sustainable forest management under future climate scenarios
Herminium gongshanense (Orchidaceae), a new species from China
No full textA new species of Herminium (Orchidaceae) from China, H. gongshanense, is described and illustrated based on morphological characters and molecular systematics. Herminium gongshanense is rather isolated in Herminium and morphological similar to H. singulum but differs from it by having peduncle without bract-like leaflet, lip 3-lobed, lateral-lobes enclosing column, staminodes filamentous and half of column. Molecular phylogenetic results based on one nuclear marker (nrITS) and two plastid markers (matK and rbcL) indicated that H. gongshanense is sister to the remaining Herminium
A Novel Prognostic Four-Gene Signature of Breast Cancer Identified by Integrated Bioinformatics Analysis
No full textMolecular analysis facilitates the prediction of overall survival (OS) of breast cancer and decision-making of the treatment plan. The current study was designed to identify new prognostic genes for breast cancer and construct an effective prognostic signature with integrated bioinformatics analysis. Differentially expressed genes in breast cancer samples from The Cancer Genome Atlas (TCGA) dataset were filtered by univariate Cox regression analysis. The prognostic model was optimized by the Akaike information criterion and further validated using the TCGA dataset (n=1014) and Gene Expression Omnibus (GEO) dataset (n=307). The correlation between the risk score and clinical information was assessed by univariate and multivariate Cox regression analyses. Functional pathways in relation to high-risk and low-risk groups were analyzed using gene set enrichment analysis (GSEA). Four prognostic genes (EXOC6, GPC6, PCK2, and NFATC2) were screened and used to construct a prognostic model, which showed robust performance in classifying the high-risk and low-risk groups. The risk score was significantly related to clinical features and OS. We identified 19 functional pathways significantly associated with the risk score. This study constructed a new prognostic model with a high prediction performance for breast cancer. The four-gene prognostic signature could serve as an effective tool to predict prognosis and assist the management of breast cancer patients