增温条件下花粉来源对红雉凤仙花生殖成功的影响

花粉来源影响着植物的生殖成功和种群的遗传结构, 母体效应则有利于子代适应母代经历的环境。然而, 气候变暖背景下, 花粉来源联合母体效应对植物生殖成功的影响仍不明了。该研究以兼性异交的中国特有植物红雉凤仙花(Impatiens oxyanthera)为研究对象, 采用双因素随机区组设计, 设置母代增温(+0 ℃和+2 ℃)嵌套子代增温(+0 ℃、+2 ℃和+4 ℃)共6种实验处理, 探讨不同母代增温条件下子代增温对红雉凤仙花花粉来源限制的影响。结果显示: 红雉凤仙花异交的结实率和种子数均高于自交的相应值, 且随着子代增温幅度提升, 这2个值均呈现不同程度降低, 特别是自交结实率和种子数随子代增温明显降低, 而母代增温则减缓了自交引起的生殖成功率降低的效应。上述结果说明, 红雉凤仙花异交生殖成功率大于自交。子代增温显著降低了兼性异交植物自交的适合度, 母代增温可以减缓这种不利影响, 从而表现出对增温的跨代适应性。     

Investigation of the source‐detector separation in near infrared spectroscopy for healthy and clinical applications

Understanding near infrared light propagation in tissue is vital for designing next generation optical brain imaging devices. Monte Carlo (MC) simulations provide a controlled mechanism to characterize and evaluate contributions of diverse near infrared spectroscopy (NIRS) sensor configurations and parameters. In this study, we developed a multilayer adult digital head model under both healthy and clinical settings and assessed light‐tissue interaction through MC simulations in terms of partial differential pathlength, mean total optical pathlength, diffuse reflectance, detector light intensity and spatial sensitivity profile of optical measurements. The model incorporated four layers: scalp, skull, cerebrospinal‐fluid and cerebral cortex with and without a customizable lesion for modeling hematoma of different sizes and depths. The effect of source‐detector separation (SDS) on optical measurements' sensitivity to brain tissue was investigated. Results from 1330 separate simulations [(4 lesion volumes × 4 lesion depths for clinical +3 healthy settings) × 7 SDS × 10 simulation = 1330)] each with 100 million photons indicated that selection of SDS is critical to acquire optimal measurements from the brain and recommended SDS to be 25 to 35 mm depending on the wavelengths to obtain optical monitoring of the adult brain function. The findings here can guide the design of future NIRS probes for functional neuroimaging and clinical diagnostic systems.      

城市绿地系统内外CO2浓度、δ13C、δ18O差异和来源及影响因素

采用离轴积分腔输出光谱技术测定夏季和冬季北京市4环路和北京园林科学研究院绿地系统空气中CO₂浓度、δ¹³C和δ¹⁸O值,在半小时尺度上分析了其变化特征和差异以及与车流量和气象因子的关联.结果表明： 4环路上车流量较大,夏季和冬季观测期间每日均超过15万辆次,有明显的早晚交通高峰.4环路与绿地系统的空气中CO₂浓度呈双峰曲线日变化,δ¹³C值呈双波谷曲线、δ¹⁸O值呈单波谷曲线日变化,夏季二者空气中的CO₂浓度、δ¹³C和δ¹⁸O差值远大于冬季.同位素定量区分结果显示,夏季观测期间4环路空气中CO₂主要来源于机动车尾气,约占64.9%,而绿地系统空气中CO₂主要来源于自养和异养呼吸,约占56.3%,冬季观测期间二者空气中CO₂均主要来源于机动车尾气.逐步回归分析表明,在半小时尺度上车流量和太阳辐射对绿地系统与4环路CO₂浓度差值产生显著影响,太阳辐射和相对湿度则是影响δ¹³C和δ¹⁸O差值的主要气象因子.绿地系统中的植物在生长季节通过光合作用吸收和消减化石燃料燃烧产生的CO₂来维持城市碳氧平衡,在改善城市生态环境方面发挥重要作用.     

Concentration,Distribution, Source,and Risk Assessment of PAHs and Heavy Metals in Surface Water from the Three Gorges Reservoir,China

Fifteen polycyclic aromatic hydrocarbons (PAHs) and heavy metals (Cr, Ni, As, Cd, Pb, and Hg) were quantified in 19 surface water sites of the Three Gorges Reservoir, China. The total concentrations of 15 PAHs and six heavy metals in the 19 sample sites ranged from 130.8 ng L^?1 to 227.5 ng L^?1 and 3.2 μg L^?1 to 6.0 μg L^?1, respectively. The mean concentration of As was the highest among the six heavy metals (2.1 ± 0.3 μg L^?1), followed by Cr (0.5 ± 0.3 μg L^?1), Ni (1.3 ± 0.1 μg L^?1), Cd (0.2 ± 0.01 μg L^?1), Pb (0.07 ± 0.08 μ g L^?1) and Hg (0.05 ± 0.08 μg L^?1). The isomer ratio results suggest that PAHs at most sites were mainly from petroleum combustion, while coal and biomass combustion was the main source at sites 1, 2, 6, 7, 9, 14, and 17. Based on principal component analysis, the main source of heavy metals was anthropogenic activities and weathering of bedrocks. Depending on characteristic of RQ_(NCs) ≥ 1 and RQ_(MPCs) < 1, BaA showed higher potential ecological risk than other PAHs, therefore, all sampling site needed to be paid much more attention, included some remedial actions. Meanwhile, after assessing human health risk of heavy metal, it was unlikely to experience adverse health effects, even exposing through more pathways and six kinds of heavy metals simultaneously.     

Plant water uptake along a diversity gradient provides evidence for complementarity in hydrological niches

Biodiversity enhances a variety of ecosystem processes, and yet the underlying mechanisms through which these relationships occur remain a critical knowledge gap. Here, we used the natural abundance of stable isotopes to measure depth of water uptake in five common grassland species (Asclepias tuberosa, Lespedeza capitata, Liatris aspera, Schizachyrium scoparium and Sorghastrum nutans) growing across an experimental grassland diversity gradient. Using this approach, we addressed the following questions: 1) does the depth‐specific provenance of water uptake differ among species and/or do interspecific differences in water source manifest with increasing community diversity? 2) Does the isotopic niche space occupied by plants change with increasing diversity? 3) Is plasticity in water uptake depth across a diversity gradient associated with functional plant responses? We found that the depth of soil water used by plants was inherently different among species when grown in monocultures. All species used less shallow soil water and more intermediate‐depth soil water in mixed assemblages than in monocultures, resulting in similar interspecific differences in water source across the diversity gradient. However, plasticity in the locations of water used were positively associated with increases in plant growth in higher diversity treatments. These results indicate that plasticity in water‐use may contribute to positive biodiversity–productivity relationships commonly observed in temperate grasslands.     

Grape berry position affects the diurnal dynamics of its metabolic profile

Solar irradiance and air temperature are characterized by dramatic circadian fluctuations and are known to significantly modulate fruit composition. To date, it remains unclear whether the abrupt, yet predictive, diurnal changes in radiation and temperature prompt direct metabolic turn‐over in the fruit. We assessed the role of fruit insolation, air temperature, and source‐tissue CO₂ assimilation in the diurnal compositional changes in ripening grape berries. This was performed by comparing the diurnal changes in metabolite profiles of berries positioned such that they experienced (a) contrasting diurnal solar irradiance patterns, and (b) similar irradiance but contrasting diurnal CO₂ assimilation patterns of adjacent leaves. Grape carbon levels increased during the morning and decreased thereafter. Sucrose levels decreased throughout the day and were correlated with air temperature, but not with the diurnal pattern of leaf CO₂ assimilation. Tight correlation between sucrose and glucose‐6‐phosphate indicated the involvement of photorespiration/glycolysis in sucrose depletion. Amino acids, polyamines, and phenylpropanoids fluctuated diurnally, and were highly responsive to the diurnal insolation pattern of the fruit. Our results fill the knowledge gap regarding the circadian pattern of source‐sink assimilate‐translocation in grapevine. In addition, they suggest that short‐term direct solar exposure of the fruit impacts both its diurnal and nocturnal metabolism.     

Voltage-clamp fluorometry in the local environment of the C255-C511 disulfide bridge of the Na+/glucose cotransporter

We recently identified a functionally important disulfide bridge between C255 and C511 of the human Na+/glucose cotransporter SGLT1. In this study, voltage-clamp fluorometry was used to characterize the fluorescence of four different dyes attached to C255 and C511 under various ionic and substrate/inhibitor conditions. State-dependent fluorescence changes (DeltaF) were observed when TMR5M or TMR6M dyes were attached to C255 and C511 or when Alexa488 was bound to C511. TMR5M-C511 was extremely sensitive to membrane potential (Vm) and to external Na+ and alphaMG (a nonmetabolizable glucose analog) concentrations. A progressive increase in alphaMG concentration drastically changed the maximal voltage-dependent DeltaF and produced a positive shift in the midpoint of the DeltaF-Vm curve. By determining specific fluorescence intensity for each state of the cotransporter, our steady-state fluorescence data could be reproduced using the rate constants previously proposed for a five-state kinetic model exclusively derived from electrophysiological measurements. Our results bring an independent support to the proposed kinetic model and show that the binding of alphaMG substrate significantly modifies the environment of C255 and C511.     

Mutational analysis of conserved aromatic residues in the A-loop of the ABC transporter ABCB1A (mouse Mdr3)

The A-loop is a recently described conserved region in the NBDs of ABC transporters [Ambudkar, S.V., Kim, I.-W., Xia, D. and Sauna, Z.E. (2006) The A-loop, a novel conserved aromatic acid subdomain upstream of the Walker A motif in ABC transporters, is critical for ATP binding. FEBS Lett. 580, 1049-1055; Kim, I.W., Peng, X.H., Sauna, Z.E., FitzGerald, P.C., Xia, D., Muller, M., Nandigama, K. and Ambudkar, S.V. (2006) The conserved tyrosine residues 401 and 1044 in ATP sites of human P-glycoprotein are critical for ATP binding and hydrolysis: evidence for a conserved subdomain, the A-loop in the ATP-binding cassette. Biochemistry 45, 7605-7616]. In mouse P-glycoprotein (Abcb1a), the aromatic residue of the A-loop in both NBDs is a tyrosine: Y397 in NBD1 and Y1040 in NBD2. Another tyrosine residue (618 in NBD1 and 1263 in NBD2) also appears to lie in proximity to the ATP molecule. We have mutated residues Y397, Y618, Y1040, and Y1263 to tryptophan and analyzed the effect of these substitutions on transport properties, ATP binding, and ATP hydrolysis by Abcb1a (mouse Mdr3). Y618W and Y1263W enzymes had catalytic characteristics similar to WT Abcb1a. On the other hand, Y397W and Y1040W showed impaired transport and greatly reduced ATPase activity, including a approximately 10-fold increase in Km for MgATP. Thus, Y397 and Y1040 play an important role in Abcb1a catalysis.     

Carbon source utilization and accumulation of respiration-related substances by freshwater Thioploca species

Carbon source utilization of Thioploca species from freshwater and brackish lakes in Japan was investigated. Microautoradiography demonstrated that freshwater and brackish Thioploca samples assimilate acetate. In addition, vertical nitrate transportation by freshwater Thioploca was examined by measuring substances accumulated in Thioploca filaments. The filaments of Thioploca sp. from Lake Biwa, a Japanese mesotrophic lake, contained nitrate at concentrations higher than ambient by two to three orders of magnitude. They also accumulated high concentrations of sulfate and abundant elemental sulfur. The results suggest that the Thioploca-specific strategy for sulfur oxidation, migration with accumulated nitrate, is effective even in freshwater habitats of lower sulfide supply.