No photosynthetic down-regulation in sweetgum trees (Liquidambar styraciflua L.) after three years of CO2 enrichment at the Duke Forest FACE experiment

Photosynthetic capacity and leaf properties of sun and shade leaves of overstorey sweetgum trees (Liquidambar styraciflua L.) were compared over the first 3 years of growth in ambient or ambient + 200 μL L^?1 CO₂ at the Duke Forest Free Air CO₂ Enrichment (FACE) experiment. We were interested in whether photosynthetic down‐regulation to CO₂ occurred in sweetgum trees growing in a forest ecosystem, whether shade leaves down‐regulated to a greater extent than sun leaves, and if there was a seasonal component to photosynthetic down‐regulation. During June and September of each year, we measured net photosynthesis (A) versus the calculated intercellular CO₂ concentration (C_i) in situ and analysed these response curves using a biochemical model that described the limitations imposed by the amount and activity of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Vc_max) and by the rate of ribulose‐1,5‐bisphosphate (RuBP) regeneration mediated by electron transport (J_max). There was no evidence of photosynthetic down‐regulation to CO₂ in either sun or shade leaves of sweetgum trees over the 3 years of measurements. Elevated CO₂ did not significantly affect Vc_max or J_max. The ratio of Vc_max to J_max was relatively constant, averaging 2·12, and was not affected by CO₂ treatment, position in the canopy, or measurement period. Furthermore, CO₂ enrichment did not affect leaf nitrogen per unit leaf area (N_a), chlorophyll or total non‐structural carbohydrates of sun or shade leaves. We did, however, find a strong relationship between N_a and the modelled components of photosynthetic capacity, Vc_max and J_max. Our data over the first 3 years of this experiment corroborate observations that trees rooted in the ground may not exhibit symptoms of photosynthetic down‐regulation as quickly as tree seedlings growing in pots. There was a strong sustained enhancement of photosynthesis by CO₂ enrichment whereby light‐saturated net photosynthesis of sun leaves was stimulated by 63% and light‐saturated net photosynthesis of shade leaves was stimulated by 48% when averaged over the 3 years. This study suggests that this CO₂ enhancement of photosynthesis will be sustained in the Duke Forest FACE experiment as long as soil N availability keeps pace with photosynthetic and growth processes.     

The effect of air-borne ammonium sulphate onPinus nigra var.maritima in the Netherlands

Summary As a result of air pollution, considerable deposition of ammonium sulphate occurs on vegetation and soil in the vicinity of chicken farms and fields dressed with animal slurry. A clear relation exists between this ammonium sulphate deposition and the distance to certain agricultural activities. Field investigations and ecophysiological experiments both show that the needles ofPinus nigra var.maritima (Ait.) Melville take up ammonium and excrete potassium, magnesium and calcium. This often results in potassium and/or magnesium deficiencies and may lead to premature shedding of needles. The high levels of nitrogen in the needles are strongly correlated to fungal diseases.Whether the observed cation leaching will result in disturbed nutrient budgets depends mainly on soil conditions. Leaching of K, Mg and Ca from the soil, caused by ammonium sulphate, may further inhibit nutrient uptake.Field investigations show a clear correlation between increased ratios of NH₄ to K, Mg and Ca in the soil solution and the damage to pine forests.     

Relative contributions of organ shape and receptor arrangement to the design of cricket’s cercal system

Understanding the relative contributions of the shape of a sensory organ and the arrangement of receptors to the overall performance of the organ has long been a challenge for sensory biologists. We tackled this issue using the wind-sensing system of crickets, the cerci, two conical abdominal appendages covered with arrays of filiform hairs. Scanning electron microscopy coupled with 3D reconstruction methods were used for mapping of all cercal filiform hairs. The hairs are arranged according to their diameter in a way that avoids collisions with neighbours during hair deflection: long hairs are regularly spaced, whereas short hairs are both randomly and densely distributed. Particle image velocimetry showed that the variation in diameter of the cercus along its length modifies the pattern of fluid velocities. Hairs are subject to higher air flow amplitudes at the base than at the apex of the cercus. The relative importance of interactions between receptors and the air flow around the organ may explain the performance of the cricket's cercal system: it is characterised by a high density of statistically non-interacting short hairs located at the base of the cercus where sensitivity to air currents is the highest.     

Model Identification of a Micro Air Vehicle

This paper is focused on the model identification of a Micro Air Vehicle （MAV） in straight steady flight condition. The identification is based on input-output data collected from flight tests using both frequency and time dorrtain techniques. The vehicle is an in-house 40 cm wingspan airplane. Because of the complex coupled, multivariable and nonlinear dynamics of the aircraft, linear SISO structures for both the lateral and longitudinal models around a reference state were derived. The aim of the identification is to provide models that can be used in future development of control techniques for the MAV.     

Viral metagenomics reveals diverse viruses in the fecal samples of children with diarrhea

Diarrhea is the third leading cause of death in developing countries in children under the age of five. About half a million children die of diarrhea every year, most of which in developing countries. Viruses are the main pathogen of diarrhea. In China, the fecal virome of children with diarrhea has been rarely studied. Using an unbiased viral metagenomics approach, we analyzed the fecal virome in children with diarrhea. Many DNA or RNA viruses associated with diarrhea identified in those fecal samples were mainly from six families of Adenoviridae, Astroviridae, Caliciviridae, Parvoviridae, Picornaviridae, and Reoviridae. Among them, the family of Caliciviridae accounts for the largest proportion of 78.42%, following with Adenoviridae (8.94%) and Picornaviridae (8.36%). In addition to those diarrhea-related viruses that have already been confirmed to cause human diarrhea, the viruses not associated with diarrhea were also identified including anellovirus and picobirnavirus. This study increased our understanding of diarrheic children fecal virome and provided valuable information for the prevention and treatment of viral diarrhea in this area.     

Study of Saharan dust influence on PM10 measures in Sicily from 2013 to 2015

Nowadays, particulate matter, especially that with small dimension as PM₁₀, PM_2.5 and PM_1, is the air quality indicator most commonly associated with a number of adverse health effects. In this paper it is analyzed the impact that a natural event, such as the transport of Saharan dust, can have on increasing the particulate matter concentration in Sicily.Consulting the data of daily PM₁₀ concentration, acquired by air quality monitoring network belonging to “Agenzia Regionale Protezionedell’ Ambiente” (Environmental Protection Regional Agency), it was possible to analyze the trend from 2013 to 2015. The days, in which the limit value was exceeded, were subjected to combined analysis. It was based on three models: interpretations of the air masses back-trajectories, using the atmospheric model HYSPLIT (HYbrid Single-Particle Lagrangian Integrated trajectory); on the calculation of the concentration on the ground and at high altitude particulate applying DREAM model (Dust REgional atmospheric model) and on the calculation of the concentration of mineral aerosols according to the atmospheric optical thickness (AOT) applying NAAPS model (Navy Aerosol Analysis and Prediction System).The daily limit value exceedances were attributed to the transport of Saharan dust events exclusively when the three models were in agreement with each other. Identifying the natural events, it was possible to quantify the contribution of the Saharan dust and consequently the reduction of the exceedances number. To quantify the contribution of Saharan dust on daily PM₁₀ concentration, it was calculated the regional background in according to precautionary approach recommended by “Guidance on the quantification of the contribution of natural sources under the EU Air Quality Directive 2008/50/EC”, when the application of the method cannot be validated with chemical analysis, as in this case. In this study is obtained, as the most important quantitative goal, the convergence of the three models to the same result. So, is evident that exceedances of the daily limit value that occurred from 2013 to 2015 in Sicily can be attributed, in most cases, to the Saharan dust intrusion.     

广州市大气污染对两种绿化植物叶绿素荧光特性的影响

研究了广州市工业生产区 (CS)、交通枢纽区 (GC)、居民生活区 (GP)和清洁对照区 (BY)等 4个大气采样点栽种的两种绿化植物大叶紫薇 (Lagerstroemiaspeciosa)和白兰 (Micheliaalba)叶绿素荧光特性的差别。综合污染指数表明 4个研究地点的污染程度由大到小的顺序为交通枢纽区 (GC) >工业生产区 (CS) >居民生活区 (GP) >清洁对照区 (BY)。不同污染地点大叶紫薇和白兰叶片的叶绿素含量、Fv/Fm、Fv/Fo,ΦPSⅡ和qP随污染程度的加剧而减少 ,细胞膜渗漏率和qN则上升。白兰这些参数的减少或增加的幅度大于大叶紫薇。用外源NaHSO3 或MV处理这两种植物时 ,细胞渗漏率的增加量和叶绿素含量下降量都是白兰大于大叶紫薇。结果表明绿化植物叶绿体光系统II活性和膜系统完整度的下降与其生长地点污染程度的加剧是一致的 ,大叶紫薇的抗污染能力大于白兰     

Genetic diversity of upper Lake Constance whitefish Coregonus spp. under the influence of fisheries: a DNA study based on archived scale samples from 1932, 1975 and 2006

This investigation examined changes in the genetic diversity of pelagic upper Lake Constance (ULC) whitefish Coregonus wartmanni population before and after the alteration of fishery methods and management from 1932 to 2006. The study spans a period of pronounced changes in trophic status of the lake and transitions from traditional relatively unselective pelagic seine (Klusgarn) fishing to highly size‐selective nylon gillnet techniques. In addition, supportive breeding and stocking became most popular during the phase of eutrophication in the 1970s. The main hypothesis is that size‐selective fisheries and breeding lead to an overall decrease in genetic variability over time. A total of 215 archived C. wartmanni scale samples from 1932, 1975 and 2006 were analysed by genotyping 11 microsatellite loci. A comparison of population genetic parameters, including allelic richness, observed and expected heterozygosities, and estimates of effective population sizes, suggests that the genetic diversity of C. wartmanni population has not decreased. The appearance of new alleles in the gene pool in 1975 and 2006 may be indicative of admixture with other forms in the lake or with stocked allochthonous forms. Overall, the fisheries management practice in ULC, including the effects of size‐selective fisheries, supportive breeding and stocking, have not significantly altered the genetic diversity of Coregonus spp. over an 80 year period.