A plant's perspective of extremes: terrestrial plant responses to changing climatic variability

We review observational, experimental, and model results on how plants respond to extreme climatic conditions induced by changing climatic variability. Distinguishing between impacts of changing mean climatic conditions and changing climatic variability on terrestrial ecosystems is generally underrated in current studies. The goals of our review are thus (1) to identify plant processes that are vulnerable to changes in the variability of climatic variables rather than to changes in their mean, and (2) to depict/evaluate available study designs to quantify responses of plants to changing climatic variability. We find that phenology is largely affected by changing mean climate but also that impacts of climatic variability are much less studied, although potentially damaging. We note that plant water relations seem to be very vulnerable to extremes driven by changes in temperature and precipitation and that heatwaves and flooding have stronger impacts on physiological processes than changing mean climate. Moreover, interacting phenological and physiological processes are likely to further complicate plant responses to changing climatic variability. Phenological and physiological processes and their interactions culminate in even more sophisticated responses to changing mean climate and climatic variability at the species and community level. Generally, observational studies are well suited to study plant responses to changing mean climate, but less suitable to gain a mechanistic understanding of plant responses to climatic variability. Experiments seem best suited to simulate extreme events. In models, temporal resolution and model structure are crucial to capture plant responses to changing climatic variability. We highlight that a combination of experimental, observational, and/or modeling studies have the potential to overcome important caveats of the respective individual approaches.     

试论生物信息流与激光生物效应的相关性--激光生物效应分子机理研究

为了探索激光生物学效应的分子机理,以便更好的掌控和利用激光生物效应,用XeCl（308 nm）准分子紫外激光以相同变化的激光参量直接辐照有生物活性的生物大分子BTG DNA、BSA（v）蛋白质和糖Mannan.实验结果分析告知：电镜法观察到受辐照的三类生物大分子的表观结构、构象（含结构信息）和光谱法（IR、Vis-UV、FR、CD）分析指出生物大分子的内在结构部件的相关的特征峰的峰位、峰值都受影响,其变迁都与激光参量的变化相呼应;与三类生物大分子中分子内、分子间沟通与信息传递相关的氢键、糖苷键等的形成与否的类似或相同的结构部件（如-C-H、-N-H、-CH-OH、-C-O、-C =O等）其特征峰的变迁都更敏感于激光参量的改变.激光辐照生物体时,激光似生物信号分子通过它的能量以粒子性、电磁波相干性影响生物大分子的分子结构、构象（含结构信息）的稳定性、增加分子内、分子间相互沟通、信息传递,亦增加了结构部件的被修饰的可能性.进而影响着生物信息流的流量与流向和细胞信号转导的协同与整体表达,产生相应的生物效应.掌握获得功能生物大分子结构构象信息与使用适宜的激光参量的相关的关系值（阈值）是重要的关键.     

Importance of replacing the support medium for viral interferonogenesis in tissue culture]

Interferonogenesis in the cells of chick embryos induced by strain Lee of influenza B virus was studied. The levels of interferon production with and without changing the medium before the cell inoculation with the interferonogens were compared. It was shown that preliminary changing of the medium resulted in a statistically reliable increase in production of interferon as compared to that without the medium changing. It was found that the increase in the synthesis of interferon under the conditions of the maintaining medium changing was accompanied by an increase in the levels of synthesis of the cellular protein and RNA determined by incorporation of C14-leucine and H3-uridine into the acid insoluble fraction of the cells. It is concluded that metabolic changes in the cells at the moment of interferonogenesis induction due to the maintaining medium changing should be considered in estimation of the experiments on the mechanism of the virus induced interferonogenesis in the tissue culture.     

Long-Term Responses of Nutrient Budgets to Concurrent Climate-Related Stressors in a Boreal Watershed

Ecosystems - The climate of the circumpolar Boreal forest is changing rapidly, resulting in a growing frequency of wildfires and changing precipitation patterns. These climate-related stressors may...     

低温胁迫下内源脱落酸对马尾松优良种源抗寒性的调节作用

以2个马尾松优良种源苗期的叶片为材料,对系列低温梯度条件下不同种源叶片的内源ABA、内源保护酶系统的动态变化的规律以及相互作用进行研究.结果表明:在降温过程中通过内源ABA的变化来调控内源保护酶的变化趋势,并协调多种酶的相互作用来抵抗低温.内源ABA、SOD对零上低温敏感,属冷害敏感型调节物质,它们在零上低温前达到最高...     

Effect of stimulus (postsynaptic current) shape on fibre excitation.

Effects of variation of the stimulus pulse shape on the excitation of a nonmyelinated nerve fibre were studied using a mathematical model based on the Hodgkin-Huxley equations. Efficiency of smoothly changing pulses was compared with that of rectangular pulses. For pulses shorter than the time to excitation, the rate of the stimulus rise did not determine the ability of a smoothly changing pulse to excite the fibre. For a given stimulus duration, the main factor was the pulse area or the charge delivered by the pulse. The strength-duration curve for smoothly changing pulses was a nonmonotonic function, in contrast to the curve for rectangular pulses. The dependence of latency on changes in the pulse area was non-linear. It would be nonmonotonic when the pulse area variation were due to the stimulus duration or the stimulus rise duration. More that one propagating intracellular action potential (IAP) could arise upon fibre activation by a long smoothly changing threshold stimulus. Upon activation of relatively short fibres the IAP could arise not at the site of the smoothly changing stimulus injection. The rectangular pulses of long duration were more efficient than the corresponding smoothly changing ones. Irrespective of the shape, the pulses whose duration at the foot is 1-2 ms, are more suitable for a prolonged threshold fibre activation.     

Comprehension of safety signs for construction workers: comparison of existing and newly designed signs

The comprehension of safety signs for construction workers was compared among existing and improved designs. Safety signs considered were existing signs, existing signs improved by adding text, existing signs improved by adding/changing pictorials, and existing signs improved by adding/changing pictorials and text. Three hundred and eighty-four construction workers were randomized for assignments into four groups. They were working on nine constructions work sites randomly selected from work sites located in Bangkok, Thailand. The number of workers in each work site was calculated for the proportion of the sample size and then they were randomized so that equal numbers of workers were included in the four groups. The four types of safety signs and an interview form were used to test their comprehension of safety signs. For data analysis, percentages, means, standard deviations, the chi-square test, the one-way ANOVA and LSD tests were applied. The results showed that the mean comprehension scores of the existing signs improved by adding text, the existing signs improved by adding/changing pictorials, and the existing signs improved by adding/changing pictorials and text were significantly higher than those of the existing signs. In addition, the mean comprehension scores of the existing signs improved by adding text and the existing signs improved by adding/changing pictorials and text were significantly higher than those of the existing signs improved by adding/changing pictorials. The highest mean comprehension score of safety signs for the construction workers was found in the existing signs improved by adding/changing pictorials and text. These results indicated that for construction workers, the comprehension of safety signs with pictorials and explanatory text was better than that of the existing signs.     

The effect of combined magnetic fields, adjusted to ion-cyclotron resonance for Ca ions, on intensity of division in planaria

The combination of a constant (42 mkT1) and parallel to it a changing magnetic field on a frequency of 32 Hz (it corresponds to cyclotron frequency for Ca2+ ions) is shown to have a changing magnetic field amplitude-dependent effect on intensity of division in planaria. A stimulating effect has been observed at the magnitude of a changing component equal to 100 nT, but the amount of division significantly decreased at 250 nT and no impact of the magnetic field was registered at 500 nT1.     

Memory and the efficient use of information

We consider the problem of how an animal's memory should be designed in order to cope with a stochastic and changing environment. In particular we consider the problem of forming the best estimate of an unknown and possibly changing environmental parameter. Under the simple model we consider, the effect of an observation is to update this estimate using a linear operator. Two models of a changing environment are analysed. For each model we show how estimates change as a function of time elapsed and observations taken. The effect of a regular sequence of observations is also considered, and it is shown that an exponential weighting of past observations is a sufficient statistic on which to base decisions. The weighting factors are different in the two model environments considered, but each is shown to be a function of the rate at which the environment is changing.     

Plants and Global Environmental Change: A Special Issue Highlighting Younger Scientists

Humans are changing the global environment to such an extent that they are changing global climate (IPCC 2007;http://www.ipcc.ch/).     

Introduction to the symposium: responses of organisms to climate change: a synthetic approach to the role of thermal adaptation

On a global scale, changing climates are affecting ecological systems across multiple levels of biological organization. Moreover, climates are changing at rates unprecedented in recent geological history. Thus, one of the most pressing concerns of the modern era is to understand the biological responses to climate such that society can both adapt and implement measures that attempt to offset the negative impacts of a rapidly changing climate. One crucial question, to understand organismal responses to climate, is whether the ability of organisms to adapt can keep pace with quickly changing environments. To address this question, a syntheses of knowledge from a broad set of biological disciplines will be needed that integrates information from the fields of ecology, behavior, physiology, genetics, and evolution. This symposium assembled a diverse group of scientists from these subdisciplines to present their perspectives regarding the ability of organisms to adapt to changing climates. Specifically, the goals of this symposia were to (1) highlight what each discipline brings to a discussion of organismal responses to climate, (2) to initiate and foster a discussion to break barriers in the transfer of knowledge across disciplines, and (3) to synthesize an approach to address ongoing issues concerning biological responses to climate.     

The cost of changing from one activity to another

When there is a cost of changing from one activity to another it affects the temporal organization of behaviour. It is shown theoretically that the cost of changing should be allocated by an animal to the cost of the behaviour that is about to be performed. This hypothesis is confirmed for the Barbary dove (Streptopelia risoria) changing between feeding and drinking in an experimental room. The double interruption method is used to determine the position of dominance boundaries in food and water deficit space. Boundary rotation is used to determine how a cost of changing affects motivational state and therefore how the cost is allocated. Results obtained in the room experiments are shown to be comparable to results obtained in Skinner boxes in which the double interruption and dominance boundary methods have been previously used, supporting their validity.     

STOCHASTIC TEMPERATURES IMPEDE RNA VIRUS ADAPTATION

Constant environments are often assumed to favor the evolution of specialization whereas exposure to changing environments may favor the evolution of generalists. Here we explored the phenotypic and molecular changes associated with evolving an RNA virus in constant versus fluctuating temperature environments. We used vesicular stomatitis virus (VSV) to determine whether selection at a constant temperature entails a performance trade‐off at an unselected temperature, whether virus populations evolve to be generalists when selected in deterministically changing temperature environments, and whether selection under stochastically changing temperatures prevents evolved generalization, such as by constraining the ability for viruses to adaptively improve. We observed that all VSV lineages evolved at constant temperatures showed fitness gains in their selected temperature with little evidence for trade‐offs in performance in the unselected environment. Evolution in deterministically and stochastically changing temperatures led to populations with the highest and lowest overall fitness gains, respectively. Sequence analysis revealed little evidence for convergent molecular evolution among lineages within the same treatment. Across all temperature treatments, the majority of genome substitutions occurred in the G (glycoprotein) gene, suggesting that this locus for the cell‐binding protein plays a key role in dictating VSV performance under changing temperature.     

Evaluation of isolation methods and culture conditions for rat bone marrow mesenchymal stem cells

Bone marrow mesenchymal stem cells (bMSCs) are multipotent and preferred for cell therapy. However, the content of bMSCs is very low. To propagate a large number of primary bMSCs rapidly has become a prerequisite for bMSC study and application. Different methods of isolating and culturing bMSC were used and compared among groups: bMSCs of group A are isolated using direct adherence method and cultured by conventional medium changing; of group B are isolated using direct adherence method and cultured by low volume medium changing; of group C are isolated using density gradient centrifugation and cultured by conventional medium changing; of group D are isolated using density gradient centrifugation and cultured by low volume medium changing. The average population doubling time (PDT), average generation time and the cumulative cell doubling level were calculated for every group. bMSCs cultured with complete medium containing 10, 11 and 15 % FBS were allocated into group a, b and c separatedly. Cell numbers were counted everyday under a microscope, the population doubling level curve was plotted and PDT was calculated. The growth curve of bMSC in group a, b and c was made. Both density gradient centrifugation and direct adherence methods obtained relatively pure bMSCs. A larger quantity of primary bMSCs were obtained by direct adherence. bMSC proliferation was faster when cultured via the low volume medium changing method at a serum concentration of 11 % than the other methods. Isolating bMSC by direct adherence and culturing by low volume medium changing at a serum concentration of 11 % is preferential for bMSC propagation.     

“锹甲”名称的由来及中国锹甲属的中名问题

简要介绍了“锹甲科”中文名称的由来;回顾、讨论了当前国内学术界有关将中文名称“锹甲”改为“鹿甲”的争议及这种更改可能带来的结果;同时系统记述了中国锹甲科已知属的中文名称。     

Motion silences awareness of visual change

Loud bangs, bright flashes, and intense shocks capture attention, but other changes--even those of similar magnitude--can go unnoticed. Demonstrations of change blindness have shown that observers fail to detect substantial alterations to a scene when distracted by an irrelevant flash, or when the alterations happen gradually [1-5]. Here, we show that objects changing in hue, luminance, size, or shape appear to stop changing when they move. This motion-induced failure to detect change, silencing, persists even though the observer attends to the objects, knows that they are changing, and can make veridical judgments about their current state. Silencing demonstrates the tight coupling of motion and object appearance.     

An assessment of context-specificity of the CS-preexposure effect in Pavlovian excitatory and inhibitory conditioning

Non-reinforced preexposure to a to-be-conditioned stimulus (CS) results in retarded development of conditioned excitation and inhibition. In a magazine-approach preparation in rats, we explored the role of background context on this CS-preexposure effect by changing contexts after the preexposure treatment. Experiment 1 demonstrated with a typical three-group design that changing background contexts attenuated the CS-preexposure effect in conditioned excitation. Experiment 2 employed the identical design except that conditioned inhibition was the target of study. Preexposure to stimulus X retarded subsequent differentiation of responding to reinforced A trials and non-reinforced AX trials, suggesting that CS-preexposure retarded development of inhibitory conditioning. However, changing contexts did not attenuate the preexposure effect. We discuss these results in the framework of the extended comparator hypothesis.     

Near-periodic substitution and the genetic variance induced by environmental change

We investigate a model that describes the evolution of a diploid sexual population in a changing environment. Individuals have discrete generations and are subject to selection on the phenotypic value of a quantitative trait, which is controlled by a finite number of bialleic loci. Environmental change is taken to lead to a uniformly changing optimal phenotypic value. The population continually adapts to the changing environment, by allelic substitution, at the loci controlling the trait. We investigate the detailed interrelation between the process of allelic substitution and the adaptation and variation of the population, via infinite population calculations and finite population simulations. We find a simple relation between the substitution rate and the rate of change of the optimal phenotypic value.     

降雨变化对高寒草甸不同植物功能群凋落物质量及其分解的影响

凋落物分解是生态系统物质循环的重要过程, 探究降雨变化对高寒草甸不同植物功能群凋落物分解的影响, 有助于了解高寒草甸物质循环对降雨变化的响应规律和机制。该研究设置减雨90% (Pr-90)、减雨50% (Pr-50)、减雨30% (Pr-30)、自然降雨(CK)和增雨50% (Pr+50) 5个降雨处理, 采用网袋分解法, 对青藏高原东部高寒草甸的3种植物功能群(禾本科、莎草科、杂类草)及群落凋落物的化学性质、质量损失和养分释放动态进行研究。结果表明: 1)减雨处理(Pr-90、Pr-50和Pr-30)显著增加禾本科凋落物的初始氮(N)含量, 显著降低碳氮比(C:N)和木质素氮比(木质素:N); 增雨处理(Pr+50)显著增加各类型凋落物初始磷(P)含量。2)根据Olson负指数模型拟合, 不同降雨处理下, 杂类草凋落物分解最快, 分解95%的时间为3.49-7.45年; 群落和莎草科次之, 分别为4.07-8.05和4.65-7.74年; 禾本科分解最慢, 为5.84-11.18年。3)极端减雨(Pr-90)抑制各类型凋落物分解, 适度降雨变化(Pr-50、Pr-30和Pr+50)抑制禾本科分解而对莎草科、杂类草和群落无显著影响, 仅增雨(Pr+50)明显促进杂类草分解。4)各类型凋落物C释放在减雨(Pr-90和Pr-30)下受到抑制, 增雨或减雨均促进禾本科N和P释放, 对于莎草科、杂类草和群落凋落物而言, Pr-30促进N释放, Pr-90抑制P释放, Pr+50促进P释放。5)结构方程模型(SEM)表明, 质量和养分残留率受降雨量的直接负效应, 也受凋落物初始C、N、P和木质素、纤维素、半纤维素含量的间接影响。综上所述, 高寒草甸凋落物质量损失及养分释放受凋落物类型和降雨量的共同影响。考虑到禾本科分解最慢且对降雨变化的响应最为敏感, 未来应关注气候变化尤其是极端减雨下禾本科的质量损失及养分释放对高寒草甸有机质输入及C、N、P循环的影响。     

Unique design for fixed ventilated changing station

The Jackson Laboratory animal colonies present a unique challenge for the design and operation of an animal changing station that maximizes protection of animal health and welfare while also protecting the health and safety of the animal caretaker. The authors describe the modification of a fixed ventilated changing station for improved animal health, reduced ergonomic strain, and decreased allergen exposure.