生物体发育过程中细胞膜电位变化与衰老

维持一定的跨质膜电势,关乎到细胞内外物质交换的基本代谢能否顺利进行,因此是所有细胞生存的前提。这是生物的单细胞祖先发展出的有效生存手段,当进化到多细胞生物体后却遇到麻烦。多细胞生物为细胞营群居生活,在物理导体的静电荷分布规律的支配下,个体细胞所携外正内负的净电荷有向细胞集团边缘汇集的趋势,导致多数细胞失去本身所携净电荷,不能维持正常跨膜电势,从而逐渐失去活力。这可能就是多细胞生物衰老的根本原因。衰老是生物体在发育中随细胞数量增多不可避免的自然发生的效应。有证据显示以上描述的电荷分布变化过程的假说是真实存在。植物体中细胞所携电荷的汇集,以及随之发生的带电离子从高浓度区向低浓度区的扩散流失,可导致产生有趣的植物生电的现象,例如大树发电。对植物电压、电的极性、高密度电荷位点分布的测结果与此假说理论完全吻合。     

Demonstration of the root surface electrogenic ion pump activity revealed from the seasonal inversion in the phase relation between electro-radicogram and the diurnal oscillation of air temperature in a field tree (Diospyros kaki)

Re-examination of the electro-radicogram (ERG) obtained during past 10 years research (Masaki and Okamoto in Trees (Berl) 21:433–442, 2007) enabled us to discriminate the excess activity of the electrogenic ion pump in the root surface cell membrane over that of the xylem pump during most of the foliate phase. The trans-root electric potential (TRP) is defined as the difference between V _ps (electric potential difference between symplast and bulk water phase surrounding the root) and V _px (electric potential difference between symplast and xylem apoplast). The diurnal oscillation of TRP followed that of the air temperature and/or light intensity with a delay of several hours during defoliate phase. This means the superiority of the electrogenic activity of the xylem pump over that of the root surface pump. However, after leaf expansion, TRP began to oscillate inversely with the temperature change with a short delay, indicating the superiority of the electrogenic activity of the surface ion pump over that of the xylem pump. An experimental lumbering of the surroundings of the kaki tree in foliate phase prominently increased the ERG amplitude, keeping the inverted phase relation, with the increase in transpiration caused by the increased illumination. An incidental sudden fall of the temperature and illumination caused an inverse reaction.     

Long term measurement of the xylem potential by unpolarizable electrode via liquid junction

Long term recordings of bioelectric potential have often been done by a pair of conventional polarizable electrodes, especially in field works. Such electrodes are apt to produce a big potential difference due to incidental polarization. We developed an electrode system which consists of unpolarizable Ag/AgCl type electrodes, liquid salt bridges and paraffin-coated injection needle which was stuck into the xylem apoplast. To avoid the invasion of air which often cuts the liquid junction between the electrodes and the xylem fluid, a tiny hydrostatic pressure (ca. 1 kPa, 10 cm difference in water level) was always applied to the liquid in the salt bridge. This simple device enabled us to continue long ter recording of the xylem potential over two months. We present in this paper the theoretical basis to get informations, without destruction of the plant bodies, about the physiological state of the root system under-ground by the observation of the xylem potential. A model experiment was carried out to warrant the theory.     

日光温室CO2浓度变化规律研究

研究了日光温室内CO₂浓度的时空变化规律.结果表明,日光温室CO₂浓度日变化曲线通常呈不规则“U”形,有时呈不规则“W”形.冬春栽培过程中日最高CO₂浓度逐渐减小,日最低浓度和昼平均浓度先降后升,CO₂亏缺时间逐渐延长.温室内CO₂空间分布特点通常是早晨和傍晚为前部>中部>后部,近地面层>作物冠层>顶层;中午前后为前部<中部<后部,近地面层>顶层>作物冠层.影响日光温室CO₂浓度变化的主要环境因素是光照度,通风不能阻止温室内高浓度CO₂外逸和避免CO₂亏缺.幼苗期群体光合较弱、土壤呼吸旺盛,温室CO₂浓度较高;结果期群体光合旺盛、土壤呼吸衰竭,CO₂亏缺严重.     

Correlation between the seasonal changes in electrogenic activity across root xylem/symplast interface,sap-flow rate and xylem pressure in field trees (<Emphasis Type="Italic">Diospyros kaki</Emphasis>)

To investigate the seasonal changes in the physiological activity of the roots in field trees, Diospyros kaki, we carried out simultaneous and continuous measurements of the trans-root electric potential (TRP), of the rate of sap-flow with transpiration and of the xylem pressure (Px) through several years. The amplitude of the diurnal change and its temperature dependency of both TRP and Px began to increase in late January. These parameters attained their maxima in the late defoliate phase just before unfolding of new leaves at the end of March, thereafter rapidly went down to their minimal levels with increasing transpiration. The low levels continued during the foliate stage until December, and the pattern of the seasonal change in Px was inverse of that in the sap-flow rate. The role of the electrogenic ion pump activity across the interface between root-symplast and xylem vessel as a driving force for acropetal water transport is discussed in relation to those seasonal changes.     

日光温室CO2浓度变化规律研究

研究了日光温室内CO2浓度的时空变化规律。结果表明,日光温室CO2浓度日变化曲线通常呈不规则"U"形,有时呈不规则"W"形。冬春栽培过程中日最高CO2浓度逐渐减小,日最低浓度和昼平均浓度先降后升,CO2亏缺时间逐渐延长,温室内CO2空间分布特点通常是早晨和傍晚为前部>中部>后部,近地面层>作物冠层>顶层;中午前后为前部<中部<后部,近地面层>顶层>作物冠层。影响日光温室CO2浓度变化的主要环境因素是光照度,通风不能阻止温室内高浓度CO2外逸和避免CO2亏缺。幼苗期群体光合较弱、土壤呼吸旺盛,温室CO2浓度较高;结果期群体光合旺盛、土壤呼吸衰竭,CO2亏缺严重。     

Differences in climate-growth relationships between two tree species that co-occur in a seasonally dry tropical forest in Northeastern Brazil

Seasonally dry tropical forests are an important global climate regulator and represent one of main drivers of carbon sink dynamics. However, projections of climate change suggest future productivity losses and negative impacts on forest functioning. Understanding the interaction between climate variability and tree growth responses between species with different growth strategies represents a crucial challenge to forecast ecosystem functioning in the future. Here we used tree ring chronology to evaluate changes in growth and climate sensitivity of two tropical tree species that co-occur in a seasonally dry tropical forest in Brazil: Cedrela odorata and Ceiba glaziovii. Using Pearson correlations and linear regressions we explored how growth variability is correlated with local (precipitation, temperature) and global (ocean temperature and El Niño Southern Oscillation - ENSO) climatic factors. Tree growth was closely related with precipitation in C. odorata (r = 0.59) and C. glaziovii (0.24). Differences were found at monthly level, which C. odorata showing greater sensitivity in the beginning of rainy season. The South Atlantic Temperature was positively correlated with C. odorata, while ENSO was negatively correlated. Our results showed a dominant effect of precipitation on tree growth and suggest that are different growth strategies among species, which C. odorata being the most sensitive to drought and C. glaziovii more adapted with parenchyma in trunk. Therefore, C. odorata is probably more vulnerable to the deleterious effects of future climate change than C. glaziovii. Our findings highlight the importance of understanding the climate sensitivity of different seasonally dry tropical forest species, which is critical to predicting carbon dynamics in tropical regions. These also reveal that differences in sensitivity must be considered when prioritizing conservation measures for seasonally dry tropical forests.     

脉冲电场下肿瘤细胞的窗口效应

基于多层电介质模型,对于适应于球形生物细胞的脉冲电场,提出了一种等效电路模型,在相同频域下,内膜和外膜的变化趋势相同,频域分析表明,不同频谱场将引起不同的生物医学效应．我们针对癌症细胞计算了跨膜电压,并讨论了脉冲和跨膜电压以及阻抗的关系．结果表明不同的频域和不同的持续时间对细胞的内膜和外膜有选择性的影响,时域和频域的分析显示,在细胞上有一个窗口,当持续时间在10^-8～10^-6 s之间,细胞内膜的电压将高于细胞外膜的电压．窗口效应为解释生物细胞的脉冲电学效应提供了一种参考思路．     

人工饲养树鼩血液学及生化指标正常值测定及分析

目的建立人工饲养健康树鼩血液学和血液生化指标的正常值参考范围,并探讨与不同物种的血液学和血液生化值的差异及相互关系。方法应用全自动血细胞仪和生化分析仪测定140只健康成年树鼩的血液学及血液生化指标。结果雌性与雄性比较,LYM％、PLT、RDW％、GLU、CREA的差异具有显著性（JP〈0．05）,11P、CHOL、TG的差异具有极显著性（P〈0．01）,其他指标的差异不具显著性,部分指标与恒河猴、大鼠及人的相应指标存在一定的差异。结论本文建立了健康树鼩的血液学及生化指标的正常值参考范围,可为应用该动物进行科学研究时提供参考。     

Potential Changes in the Distributions of Western North America Tree and Shrub Taxa under Future Climate Scenarios

Increases in atmospheric greenhouse gases are driving significant changes in global climate. To project potential vegetation response to future climate change, this study uses response surfaces to describe the relationship between bioclimatic variables and the distribution of tree and shrub taxa in western North America. The response surfaces illustrate the probability of the occurrence of a taxon at particular points in climate space. Climate space was defined using three bioclimatic variables: mean temperature of the coldest month, growing degree days, and a moisture index. Species distributions were simulated under present climate using observed data (1951–80, 30-year mean) and under future climate (2090–99, 10-year mean) using scenarios generated by three general circulation models—HADCM2, CGCM1, and CSIRO. The scenarios assume a 1% per year compound increase in greenhouse gases and changes in sulfate (SO₄) aerosols based on the Intergovernmental Panel on Climate Change (IPCC) IS92a scenario. The results indicate that under future climate conditions, potential range changes could be large for many tree and shrub taxa. Shifts in the potential ranges of species are simulated to occur not only northward but in all directions, including southward of the existing ranges of certain species. The simulated potential distributions of some species become increasingly fragmented under the future climate scenarios, while the simulated potential distributions of other species expand. The magnitudes of the simulated range changes imply significant impacts to ecosystems and shifts in patterns of species diversity in western North America. Received 12 May 2000; accepted 20 December 2000.     

Field studies of water relations and photosynthesis in Scots pine.

Needle water potential at noon and diurnal variation in needle water potential was measured with a pressure chamber during the growth seasons (1974, 1975 and 1976) in a 20-year-old stand of Scots pine (Pinus sylvestris L.), subjected to daily irrigation and nutrient treatments at Jädraås, in central Sweden (60°50'N).
In unstressed conditions there was little difference in water potential amongst the treatments. However, during a dry spell in 1976 the diurnal curves of water potential in the control and combined irrigated and fertilized treatment diverged by up to 6 bar in the middle of the day. Irrigation alone resulted in higher midday water potentials (Ψ_n) than in the controls only during this period. At other times in 1974, 1975 and early 1976, the values of Ψ_n in the irrigated treatment were similar to the controls. Fertilization alone resulted in higher Ψ_n than in the controls in both 1975 and 1976 during both wet and dry periods. However, the largest difference between treatment and control occurred in the combined, irrigated and fertilized treatment during the dry spell in 1976.
Several possible explanations for the effect of fertilization on leaf water potential are discussed, including changes in hydraulic conductivity and water storage. The most likely explanation is a reduced transpiration rate as a result of more effective stomatal control of water loss.     

Predicting the Potential Future Distribution of Four Tree Species in Ohio Using Current Habitat Availability and Climatic Forcing

Weinvestigated the effect of habitat loss on the ability of trees to shift in distribution across a landscape dominated by agriculture. The potential distribution shifts of four tree species (Diospyros virginiana, Oxydendron arboreum, Pinus virginiana, Quercus falcata var. falcata) whose northern distribution limits fall in the southern third of Ohio were used to assess possible distribution shift scenarios as a result of global warming. Our predictions derive from the results of simulations using (a) forest inventory based estimates of current distribution and abundance of target species; (b) a satellite-based estimate of forest habitat availability; and (c) a tree migration model (SHIFT). The current distribution and abundance of trees was estimated using USDA Forest Service's Forest Inventory Analysis data and distribution maps from the late 1960s; pre-European settlement forest–nonforest maps were used to represent the fully forested condition for calibration and comparison. Habitat-availability estimates in Ohio were estimated using classified Landsat Thematic Mapper (TM) data from 1994. Tree abundance, forest availability and migration were modeled using a 1-km² pixel size. Forest availability was estimated as the proportion of forested TM pixels within each cell. The probability of a migrating species colonizing an unoccupied cell is modeled as a function of forest availability and distance to occupied cells. The results of the migration models suggest that the species studied are capable of colonizing virtually any forested location within Ohio over the next 100 years if climatic controls over the current distribution that may currently inhibit northward movement are relaxed. The contiguous distribution of these species, however, is not likely to shift more than 10 km during the next century regardless of the magnitude of the climate change. Examining the sensitivity of our simulations by varying critical model attributes, we found that whereas the variables controlling the amount of long-distance dispersal have strong effects on migration rates in the fully forested 1800 situation, they have significantly lesser effects on projections of future migration into highly fragmented forests. The low forest availability that characterizes much of the current Ohio landscape, along with the low likelihood of long distance dispersal, result in potential distribution shifts that are concentrated within the principally forested corridors in southeastern Ohio. We propose that in contrast to the past, future tree migrations are likely to be spatially and temporally correlated as a result of large climatic forcing and channelization through limited regions of available habitat. With respect to the management of biodiversity, this result suggests that it may be very difficult to discern plant migrations of native forest species owing to exceedingly slow rates of movement. Received 19 September 2000; Accepted 2 March 2001.     

Tree diversity in sacred groves of the Jaintia hills in Meghalaya, northeast India

Biodiversity of woody species was investigated in Ialong and Raliangsacred groves of the Jaintia hills in Meghalaya, northeast India. These grovesrepresent the climax subtropical broad-leaved forest of the area. A total of 738individuals belonging to 82 species, 59 genera and 39 families was identified ina 0.5 ha plot of the Ialong sacred grove, whereas the same area in theRaliang sacred grove had 469 individuals of 80 species, 62 genera and 41families. About 32% species were common to both groves. Lauraceae, with10–17 species, was the dominant family. The canopy and subcanopy stratawere respectively composed of 28 and 33% of the total tree species in theforest. The number of species as well as stem density were greater for the treesof lower dbh (5–15 cm) class compared to the higher (> 66cm) dbh class. The majority of the species showed a contagiousdistribution pattern and low frequency. The basal area varied from 57.4 to 71.4m² ha^–1. Species richness within theforest varied from 3 to 15 per 100 m² in Ialong and 3 to 12 per 100m² in Raliang. The dominance–distribution curves showed highequitability and low dominance in both groves.     

Evaluation of the Electric Field Strength in a Pre-Breakdown Ionization Wave in a Long Discharge Tube from the Emission Spectrum

Plasma Physics Reports - The paper presents the results of studying the characteristics of a slow ionization wave (IW) arising at the initial stage of breakdown in a long discharge tube under...     

Tree ring anatomy indices of Pinus tabuliformis revealed the shifted dominant climate factor influencing potential hydraulic function in western Qinling Mountains

Trees can adjust xylem anatomical structure related with potential hydraulic functions to cope with climate variability. We therefore need a better understanding of how climate variability constrains wood anatomy and tree radial growth. Pinus tabuliformis dominates natural forests and plantations over the western Qinling Mountains, which is one of the ecologically vulnerable areas in China. Here, we investigated the response of P. tabuliformis tree-ring anatomical structure to climate variability by applying wood anatomy analysis, and evaluated the influences of anatomical traits on potential hydraulic functions and the climate significance of intra-annual density fluctuations (IADFs). We found that with the increasing temperature from spring to summer, the negative effect of temperature on the formation and enlargement of earlywood and transition-wood tracheids was gradually enhanced. However, spring precipitation not only had a direct and positive influence on the formation of earlywood, but also had a delaying impact on the transition-wood cell enlargement. Besides, the smaller earlywood tracheid size of P. tabuliformis could be a substantially characteristic reflecting spring drought. The contribution of lumen diameter on conduit wall reinforcement was dominated in earlywood, while the contribution of cell wall thickness was greater than that of lumen diameter in latewood. The different contributions of anatomical traits on conduit wall reinforcement would further affect the response of potential hydraulic function to climate. IADFs of P. tabuliformis could be a potential indicator to reflect the abnormal summer precipitation events in the western Qinling Mountains. IADFs with strong and weak intensity indicated years with high and low rates of change in mid-summer precipitation, respectively. Future warmer and drier climate in the western Qinling Mountains will likely result in the production of smaller tracheids to ensure hydraulic safety, which means the stronger drought resistant of P. tabuliformis in the future. In this study, we linked the xylem anatomy and potential hydraulics functions with intra-seasonal climate variability in the context of climate warming and drying, and proposed some xylem anatomical indices reflecting potential drought events.     

Comparative Field Summer Stress of Three Tree Species Co-occurring in Mediterranean Coastal Dunes

Chlorophyll a fluorescence, water potential (_s), and root system of Juniperus oxycedrus ssp. macrocarpa, Juniperus phoenicea ssp. turbinata, and Pinus pinea were studied in Mediterranean coastal dunes of SW Spain during summer drought and after fall rains in 1999, the driest year in the 90's. A strong and reversible depression in the photochemical efficiency of photosystem 2 of the three species was recorded, which happened concomitantly with the diurnal increase and decrease in radiation. J. phoenicea, with superficial root system, was the most affected species by summer drought. It showed high rates of down-regulation of photosynthesis by photoinhibition and positive correlation between _s and F_v/F_p, with _s lower than -7 MPa. However, it tolerated this high stress, showing a fast recovery of its physiological state after fall rains. On the other hand, J. oxycedrus and P. pinea, both with deep root systems, kept their _s values up to -3 MPa, showing lower stress during summer drought. On the other hand, J. oxycedrus and J. phoenicea were more sensible to changes in edaphic water content than P. pinea. These specific responses to summer drought would be determined by their root distributions and stomatal control of transpiration, conditioning the efficiency in getting and using the available water resources. Ecophysiological responses indicate that these species are well-adapted to long periods of drought in Mediterranean climate areas, developing different strategies: J. phoenicea tolerates high stress with a fast recovery after fall rains, while J. oxycedrus and P. pinea are less affected by summer drought since their deep root systems would allow them to reach deep water resources.     

Effect of Direct-Current Electric Field on Enzymatic Activity and the Concentration of Laccase

This work investigates the effect of direct-current electric field on the extracellular enzymatic activity, concentration and other experimental parameters of laccase from Trametes versicolor. The results showed that laccase could significantly contribute to the change of pH at the end of graphite electrode. In addition, it increased the electrical conductivity of the water. In the experiment, the optimum pH and catalytic pH range for laccase activity were 3.0 and pH 2.5–4.0. The application of 6 V direct current showed significant effects on the laccase enzyme activity. The activity of laccase was enhanced in the anodic region, but at the same time was strongly inhibited at the cathode. The electric charge characteristics of laccase were changed when exposed to electric field, and some laccases molecules moved to the anode, which produced a slight migration phenomenon. This study is the basis of combination of laccase and electrical technology, at the same time, providing a new direction of enhancing laccase activity. Compared to immobilization, using electric field is simple, no chemical additives, and great potential.     

A new monitoring PAM fluorometer (<Emphasis Type="Italic">MONI-PAM</Emphasis>) to study the short- and long-term acclimation of photosystem II in field conditions

We present and evaluate the performance of a new field monitoring PAM fluorometer (MONI-PAM) which is intended for short- and long-term monitoring of the acclimation of photosystem II (PSII). The instrument measures chlorophyll fluorescence, photosynthetic photon flux density (PPFD), and temperature in the field, and monitors exactly the same leaf area over prolonged periods of time, facilitating the estimation of both rapidly reversible and sustained non-photochemical quenching (NPQ). The MONI-PAM performance is evaluated in the lab and under natural conditions in a Scots pine canopy during spring recovery of photosynthesis. The instrument provides a new tool to study in detail the acclimation of PSII to the environment under natural field conditions.     

Specific subunits of voltage-gated sodium channel underlying the subthreshold membrane potential oscillations: Potential therapeutic targets for neuropathic pain

The treatment of neuropathic pain remains a major challenge to pain clinicians. Certain nociceptive and non-nociceptive dorsal root ganglion (DRG) neurons may develop abnormal spontaneous activities following peripheral nerve injury, which is believed to be a major contributor to chronic pain. Subthreshold membrane potential oscillation (SMPO) observed in injured DRG neurons was reported to be involved in the generation of abnormal spontaneous activity. Tetrodotoxin-sensitive sodium (Na⁺) channels were testified to be involved in the generation of SMPO, but their specific subunits have not been clarified. We hypothesize that the subunits of voltage-gated sodium channel, Na_v1.3 and Na_v1.6, are involved in the generation of SMPO. An attempt to test this hypothesis may lead to a new therapeutic strategy for neuropathic pain.     

Hyperpolarization of the Membrane Potential in Cardiomyocyte Tissue Slices by the Synchronization Modulation Electric Field

Our previous studies have shown that a specially designed, so-called synchronization modulation electric field can entrain active transporter Na/K pumps in the cell membrane. This approach was previously developed in a study of single cells using a voltage clamp to monitor the pump currents. We are now expanding our study from isolated single cells to aggregated cells in a 3-dimensional cell matrix, through the use of a tissue slice from the rat heart. The slice is about 150 μm in thickness, meaning the slices contain many cell layers, resulting in a simplified 3-dimensional system. A fluorescent probe was used to identify the membrane potential and the ionic concentration gradients across the cell membrane. In spite of intrinsic cell-to-cell interactions and the difficulty in stimulating cell aggregation in the tissue slice, the oscillating electric field increased the intracellular fluorescent intensity, indicating elevation of the cell ionic concentration and hyperpolarization of the cell membrane. Blockage of these changes by ouabain confirmed that the results are directly related to Na/K pumps. These results along with the backward modulation indicate that the synchronization modulation electric field can influence the Na/K pumps in tissue cells of a 3-dimensional matrix and therefore hyperpolarize the cell membrane.