Intra- and intersexual interactions shape microbial community dynamics in the rhizosphere of Populus cathayana females and males exposed to excess Zn

In this study, we intended to investigate the responses of rhizospheric bacterial communities of Populus cathayana to excess Zn under different planting patterns. The results suggested that intersexual and intrasexual interactions strongly affect plant growth and Zn extraction in both sexes, as well as rhizosphere-associated bacterial com-munity structures. Females had a higher capacity of Zn accumulation and translocation than males under all planting patterns. Males had lower Zn accumulation and translocation under intersexual than under intrasexual interaction; the contrary was true for females. Females harbored abundant Streptomyces and Nocardioides in their rhizosphere, similarly to males under intersexual interaction, but differed from single-sex males under excess Zn. Conversely, intersexual interaction increased the abundance of key taxa Actinomycetales and Betaproteobacteria in both sexes exposed to excess Zn. Males improved the female rhizospheric microenvironment by increasing the abundance of some key tolerance taxa of Chloroflexi, Proteobacteria and Actinobacteria in both sexes under excess Zn in intersexual interaction. These results indicated that the sex of neighboring plants affected sexual differences in the choice of specific bacterial colonizations for phytoextraction and tolerance to Zn-contaminated soils, which might regulate the spatial segregation and phytoremediation potential of P. cathayana females and males under heavy metal contaminated soils.Peer reviewe

Ammonium and nitrate affect sexually different responses to salt stress in Populus cathayana

Nitrogen (N) fertilization is a promising approach to improve salt tolerance. However, it is poorly known how plant sex and inorganic N alter salt stress-induced Na+ uptake, distribution and tolerance. This study employed Populus cathayana Rehder females and males to examine sex-related mechanisms of salt tolerance under nitrate (NO3-) and ammonium (NH4+) nutrition. Males had a higher root Na+ efflux, lower root-to-shoot translocation of Na+, and higher K+/Na+, which enhanced salt tolerance under both N forms compared to females. On the other hand, decreased root Na+ efflux and K+ retention, and an increased ratio of Na+ in leaves relative to shoots in females caused greater salt sensitivity. Females receiving NH4+ rather than NO3- had greater net root Na+ uptake, K+ efflux, and translocation to the shoots, especially in leaves. In contrast, males receiving NO3- rather than NH4+ had increased Na+ translocation to the shoots, especially in the bark, which may narrow the difference in leaf damage by salt stress between N forms despite a higher shoot Na+ accumulation and lower root Na+ efflux. Genes related to cell wall synthesis, K+ and Na+ transporters, and denaturized protein scavenging in the barks showed differential expression between females and males in response to salt stress under both N forms. These results suggested that the regulation of N forms in salt stress tolerance was sex-dependent, which was related to the maintenance of the K+/Na+ ratio in tissues, the ability of Na+- translocation to the shoots, and the transcriptional regulation of bark cell wall and proteolysis profiles.Peer reviewe

Sex-specific nitrogen allocation tradeoffs in the leaves of Populus cathayana cuttings under salt and drought stress

Nitrogen (N) partitioning within a leaf affects leaf photosynthesis and adaptation to environmental fluctuations. However, how plant sex influences leaf N allocation and its tradeoffs in acclimation to drought, excess salt and their combination remains unknown. Here, leaf N allocation between the photosynthetic and non-photosynthetic apparatus and among the components of the photosynthesis in Populus cathayana Rehder females and males were investigated under drought, salt and their combination to clarify the underlying mechanism. We found that males with a lower leaf N allocation (NL) into non-protein N (Nnp), showed a greater leaf N allocation into photosynthetic apparatus, especially into the carboxylation component under all treatments, and a greater leaf N allocation into cell wall under drought and salt stress alone, consequently causing higher photosynthetic N use efficiency (PNUE) and tolerance to stresses. Conversely, females had a greater leaf N allocation into Nnp under all treatments than males and a lower leaf photosynthetic N (NP) allocation. There was a tradeoff in leaf N allocation among photosynthetic apparatus (NP/NL), cell wall (NCW/NL) and Nnp, which explained plant responses to drought, salt and their combination. Moreover, the leaf N allocation into the carboxylation component could explain the intersexual difference in responses to all treatments, while leaf cell wall N (NCW) and Nnp reflected intrasexual differences among treatments in both sexes. These findings indicate sex-specific strategies in coping with drought, salt and their combination that relate to leaf N allocation, which may contribute to sex-specific photosynthesis and niche segregation.Peer reviewe

Analysis of Traffic Operation Performances at Roundabouts

AbstractThe traffic operation performances at roundabouts are complicated under the influence of confluence operations. On the basis of the Mengxi square in Zhenjiang city roundabouts survey using video cameras, some parameter performances of different vehicle types on weaving sections and circulating lanes are analyzed, which included the velocity distribution, the gap distribution, as well as the distance distribution of lane changing. Based on the analysis, some of the conclusions are as follows: 1) The vehicle velocity of inner circulating lane is larger than the outer circulating lane 2) The entry vehicle velocity is smallest 3) The distribution of entry gaps is different from circulating gaps 4) the characteristics of vehicle teams are mostly same in different lanes 5) When the type is bigger, the lane changing distance is smaller 6) For the same type, the distance of lane changing shows ladder-like distribution.The research result will be a base for improving the capacity of roundabouts

Anatomical variation of mesophyll conductance due to salt stress in Populus cathayana females and males growing under different inorganic nitrogen sources

Synergistic regulation in leaf architecture and photosynthesis is essential for salt tolerance. However, how plant sex and inorganic nitrogen sources alter salt stress-dependent photosynthesis remains unknown. Leaf anatomical characteristics and photosynthesis of Populus cathayana Rehder females and males were investigated under salt stress conditions combined with nitrate NO3- and ammonium NH4+ supplies to clarify the underlying mechanisms. In salt-stressed females, we observed an increased mesophyll spongy cell density, a reduced chloroplast density, a decreased surface area of chloroplasts adjacent to the intercellular air space (S-c/S) and an increased mesophyll cell area per transverse section width (S/W), consequently causing mesophyll conductance (g(m)) and photosynthesis inhibition, especially under NH4+ supply. Conversely, males with a greater mesophyll palisade tissue thickness and chloroplast density, but a lower spongy cell density had lower S/W and higher S-c/S, and higher g(m) and photosynthesis. NH4+-fed females had a lower CO2 conductance through cell wall and stromal conductance perpendicular to the cell wall, but a higher chloroplast conductance from the cell wall (g(cyt1)) than females supplied with NO3-, whereas males had a higher chloroplast conductance and lower CO2 conductance through cell wall when supplied with NO3- instead of NH4+ under salt stress. These findings indicate sex-specific strategies in coping with salt stress related to leaf anatomy and g(m) under both types of nitrogen supplies, which may contribute to sex-specific CO2 capture and niche segregation.Peer reviewe

Microstructural and physiological responses to cadmium stress under different nitrogen levels in Populus cathayana females and males

Although increasing attention has been paid to the relationships between heavy metal and nitrogen (N) availability, the mechanism underlying adaptation to cadmium (Cd) stress in dioecious plants has been largely overlooked. This study examined Cd accumulation, translocation and allocation among tissues and cellular compartments in Populus cathayana Rehder females and males. Both leaf Cd accumulation and root-to-shoot Cd translocation were significantly greater in females than in males under a normal N supply, but they were reduced in females and enhanced in males under N deficiency. The genes related to Cd uptake and translocation, HMA2, YSL2 and ZIP2, were strongly induced by Cd stress in female roots and in males under a normal N supply. Cadmium largely accumulated in the leaf blades of females and in the leaf veins of males under a normal N supply, while the contrary was true under N deficiency. Furthermore, Cd was mainly distributed in the leaf epidermis and spongy tissues of males, and in the leaf palisade tissues of females. Nitrogen deficiency increased Cd allocation to the spongy tissues of female leaves and to the palisade tissues of males. In roots, Cd was preferentially distributed to the epidermis and cortices in both sexes, and also to the vascular tissues of females under a normal N supply but not under N deficiency. These results suggested that males possess better Cd tolerance compared with females, even under N deficiency, which is associated with their reduced root-to-shoot Cd translocation, specific Cd distribution in organic and/or cellular compartments, and enhanced antioxidation and ion homeostasis. Our study also provides new insights into engineering woody plants for phytoremediation.Peer reviewe

Lithofacies paleogeography mapping and reservoir prediction in tight sandstone strata: A case study from central Sichuan Basin, China

AbstractSand-rich tight sandstone reservoirs are potential areas for oil and gas exploration. However, the high ratio of sandstone thickness to that of the strata in the formation poses many challenges and uncertainties to traditional lithofacies paleogeography mapping. Therefore, the prediction of reservoir sweet spots has remained problematic in the field of petroleum exploration. This study provides new insight into resolving this problem, based on the analyses of depositional characteristics of a typical modern sand-rich formation in a shallow braided river delta of the central Sichuan Basin, China. The varieties of sand-rich strata in the braided river delta environment include primary braided channels, secondary distributary channels and the distribution of sediments is controlled by the successive superposed strata deposited in paleogeomorphic valleys. The primary distributary channels have stronger hydrodynamic forces with higher proportions of coarse sand deposits than the secondary distributary channels. Therefore, lithofacies paleogeography mapping is controlled by the geomorphology, valley locations, and the migration of channels. We reconstructed the paleogeomorphology and valley systems that existed prior to the deposition of the Xujiahe Formation. Following this, rock-electro identification model for coarse skeletal sand bodies was constructed based on coring data. The results suggest that skeletal sand bodies in primary distributary channels occur mainly in the valleys and low-lying areas, whereas secondary distributary channels and fine deposits generally occur in the highland areas. The thickness distribution of skeletal sand bodies and lithofacies paleogeography map indicate a positive correlation in primary distributary channels and reservoir thickness. A significant correlation exists between different sedimentary facies and petrophysical properties. In addition, the degree of reservoir development in different sedimentary facies indicates that the mapping method reliably predicts the distribution of sweet spots. The application and understanding of the mapping method provide a reference for exploring tight sandstone reservoirs on a regional basis

Analysis on Residents’ Travel Activity Pattern in Historic Urban Areas: A Case Study of Historic Urban Area of Yangzhou, China

Travel behaviors and activity patterns in the historic urban area of a city are expected to be different from the overall situations in the city area. The primary objective of this study is to analyze the residents’ travel activity patterns in historic urban area. Based on survey data conducted in the historic urban area of Yangzhou, the travel activities of local residents in a whole day were classified into five types of patterns. The multinomial logit (MNL) model was developed to evaluate the impacts of explanatory variables on the choices of activity patterns. The results showed that the choice of activity pattern was significantly impacted by five contributing factors including the gender, age, occupation, car ownership, and number of electric bikes in household. The other variables, which were the family population, preschoolers, number of conventional bikes in household, motorcycle ownership, and income, were found to be not significantly related to the choice of activities. The results of this study from historic urban area were compared to findings of previous studies from overall urban area. The comparison showed that the impacts of factors on activity pattern in the historic urban area were different from those in the overall area. Findings of this study provide important suggestions for the policy makings to improve the traffic situations in historic urban areas of cities

Stress-dependent magnetic flux leakage: finite element modelling simulations versus experiments

Assessing the effect of defect induced stresses on magnetic flux leakage (MFL) signals is a complicated task due to nonlinear magnetomechanical coupling. To facilitate the analysis, a multi-physics finite elemental simulation model is proposed based on magnetomechanical theory. The model works by quasi-statically computing the stress distribution in the specimen, which is then inherited to solve the nonlinear magnetic problem dynamically. The converged solution allows identification and extraction of the MFL signal induced by the defect along the sensor scanning line. Experiments are conducted on an AISI 1045 steel specimen, i.e. a dog-bone shaped rod with a cylindrical square-notch defect. The experiments confirm the validity of the proposed model that predicted a linear dependency of the peak-to-peak amplitude of the normalized MFL signal on applied stress. Besides identifying the effect of stress on the induced MFL signal, the proposed model is also suitable for solving the inverse problem of sizing the defects when stress is involved