Acclimation to irradiance of leaf photosynthesis and associated nitrogen reallocation in photosynthetic apparatus in the year following thinning of a young stand of Chamaecyparis obtusa

In order to quantify the effects of thinning on photosynthetic parameters and associated change in leaf nitrogen (N) contents, half of the trees in a 10-year-old Chamaecyparis obtusa (Sieb. et Zucc.) Endl. stand (36° 3′N, 140°7′E) were removed, giving a final density of 1 500 trees ha⁻¹, in May 2004. Photosynthetic photon flux density (PPFD) and leaf N and carbon (C) contents in the lower (L), middle (M), and upper (U) crowns were monitored one, three, and five months after thinning in both the thinned stand and a non-thinned control stand. In addition, leaves’ photosynthetic responses to CO₂ concentration were simultaneously measured in situ to estimate the maximum rates of carboxylation (V_cmax) and electron transport (J_max). Thinning increased PPFD in the L and M crowns but not in the U crown. V_cmax in both the L and M crowns of the thinned stand increased significantly in comparison with the same crown position of the control stand in the three and five months following thinning. In addition, the thinned stand exhibited an increase in N partitioned to ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) in the L and M crowns relative to the control stand three and five months after thinning, indicating that N had been redistributed within the photosynthetic machinery. Thinning did not affect N per unit area at any of the crown positions, but significantly increased the content of N as a fraction of the total leaf dry mass in the L and M crowns three and five months after thinning. This was a consequence of a decrease in leaf dry mass due to rapid shoot growth. Thus thinning did not cause a redistribution of N between leaves. Thinning improved irradiance in the L and M crowns of C. obtusa, leading to photosynthetic acclimation. Photosynthetic acclimation in the first year mainly occurred via redistribution of N within but not between leaves.     

Responses of photosynthetic parameters of Quercus mongolica to soil moisture stresses

The effect of drought on plant photosynthetic parameters has not been quantitatively described in the models of plant photosynthetic mechanism, so the seedlings of Quercus mongolica from Northeast China were used to study the responses of the photosynthetic parameters to soil water stresses. The results showed that the relationship between the maximum net leaf photosynthetic rate (P_max) of Quercus mongolica and soil moisture could be expressed as a quadratic curve (P < 0.01), and P_max reached the maximum when soil volume moisture was close to 35.45% of the field water holding capacity. The maximum rate of carboxylation (V_cmax), the maximum potential rate of electron transport (J_max) and triose phosphate utilization (TPU) rate of Quercus mongolica also had quadratic relationships with soil water content (P < 0.01). Namely, V_cmax, J_max and TPU had similar response curves to soil water, but had different optimal soil water contents. Based on the temperature and responses of plant photosynthetic parameters to water, this function provides researchers with the parameters and methodology for understanding and simulating the responses of plant photosynthetic parameters to drought stress.     

Responses of photosynthetic parameters of Quercus mongolica to soil moisture stresses

The effect of drought on plant photosynthetic parameters has not been quantitatively described in the models of plant photosynthetic mechanism, so the seedlings of Quercus mongolica from Northeast China were used to study the responses of the photosynthetic parameters to soil water stresses. The results showed that the relationship between the maximum net leaf photosynthetic rate (P_max) of Quercus mongolica and soil moisture could be expressed as a quadratic curve (P < 0.01), and P_max reached the maximum when soil volume moisture was close to 35.45% of the field water holding capacity. The maximum rate of carboxylation (V_cmax), the maximum potential rate of electron transport (J_max) and triose phosphate utilization (TPU) rate of Quercus mongolica also had quadratic relationships with soil water content (P < 0.01). Namely, V_cmax, J_max and TPU had similar response curves to soil water, but had different optimal soil water contents. Based on the temperature and responses of plant photosynthetic parameters to water, this function provides researchers with the parameters and methodology for understanding and simulating the responses of plant photosynthetic parameters to drought stress.     

蒙古栎(Quercus mongolica)光合参数对水分胁迫的响应机理

针对当前植物光合机理模型中植物光合参数没有考虑干旱胁迫影响的不足,以东北地区蒙古栎为研究对象,基于蒙古栎对不同水分响应的植物生理生态模拟试验,探讨了蒙古栎光合参数对水分胁迫的定量响应.结果表明,水分胁迫严重影响蒙古栎叶片的光合参数.其最大净光合速率(Pmax)与土壤含水量呈抛物线关系(P<0.01),且在土壤体积含水量35.45%(相当于土壤质量含水量23.63%)接近田间持水量(27.4%)时达到最大值.蒙古栎幼苗叶片的最大羧化速率(Vcmax)、最大电子传递速率(Jmax)和磷酸丙糖利用率(TPU)均与土壤水分呈抛物线关系(P<0.01),即Vcmax、Jmax 、TPU对土壤水分具有相同的响应趋势,但各光合参数达到最大时的土壤水分阈值却不相同.同时,基于蒙古栎光合作用参数对水分变化响应的定量分析,建立了水热因子协同影响的植物光合参数模型,为最终建立适用于所有植物的水热因子协同影响的光合参数模型提供了依据与技术示范.     

基于东北温带落叶阔叶林通量数据的BEPS 模型参数优化

控制其他参数为经验常数,利用迭代方法对主要光合作用参数最大羧化速率(V_{c max}) 及最大电子传递速率(J_max)进行不同数值组合,将得到的多组模拟结果的逐日总初级生产力(GPP)分别与东北帽儿山落叶阔叶林的通量观测数据进行比较,实现对小时步长BEPSHourly模型V_{c max}和J_max的参数优化.结果表明: 对于东北温带落叶阔叶林,当V_{c max}为41.1 μmol·m^-2·s^-1、J_max 为82.8 μmol·m^-2·s^-1时,模拟的2011年逐日GPP与观测数据比较的均方根误差(RMSE)最小,为1.10 g C·m^-2·d^-1,R²最高,为0.95.经过光合作用参数V_{c max}和J_max优化后,BEPSHourly模型能更好地模拟GPP的季节变化.     

Plasma osmolality and oxygen consumption of perch Perca fluviatilis in response to different salinities and temperatures

The present study determined the blood plasma osmolality and oxygen consumption of the perch Perca fluviatilis at different salinities (0, 10 and 15) and temperatures (5, 10 and 20° C). Blood plasma osmolality increased with salinity at all temperatures. Standard metabolic rate (SMR) increased with salinity at 10 and 20° C. Maximum metabolic rate (MMR) and aerobic scope was lowest at salinity of 15 at 5° C, yet at 20° C, they were lowest at a salinity of 0. A cost of osmoregulation (SMR at a salinity of 0 and 15 compared with SMR at a salinity of 10) could only be detected at a salinity of 15 at 20° C, where it was 28%. The results show that P. fluviatilis have capacity to osmoregulate in hyper‐osmotic environments. This contradicts previous studies and indicates intraspecific variability in osmoregulatory capabilities among P. fluviatilis populations or habitat origins. An apparent cost of osmoregulation (28%) at a salinity of 15 at 20° C indicates that the cost of osmoregulation in P. fluviatilis increases with temperature under hyperosmotic conditions and a power analysis showed that the cost of osmoregulation could be lower than 12·5% under other environmental conditions. The effect of salinity on MMR is possibly due to a reduction in gill permeability, initiated to reduce osmotic stress. An interaction between salinity and temperature on aerobic scope shows that high salinity habitats are energetically beneficial during warm periods (summer), whereas low salinity habitats are energetically beneficial during cold periods (winter). It is suggested, therefore, that the seasonal migrations of P. fluviatilis between brackish and fresh water is to select an environment that is optimal for metabolism and aerobic scope.     

Physiological differences of five Holm oak (Quercus ilex L.) ecotypes growing under common growth conditions were related to native local climate

An increase in the frequency and intensity of extreme climatic conditions is expected for the Mediterranean area as a response to climate change. As a consequence, the ability of Mediterranean plant species to adapt to complex and stressful environmental conditions plays an important role in driving their future distribution. The adaption of plant species may be expressed by ecotypes already adapted to local climate. Our goal was to analyse the seasonal physiological behaviour of five Quercus ilex ecotypes coming from different Italian geographical areas (from the north to the south) in order to test if ecotypes maintained their physiological traits when grown in the same environmental conditions. Measurements of gas exchange, biochemistry and chlorophyll fluorescence carried out during winter, spring and summer underlined that the response of the considered ecotypes reflected the climate of the original provenances, particularly under suboptimal conditions. The ecotypes from the northernmost and the southernmost limits were the most sensitive to high and low temperatures, respectively. Our results can be used to advance hypotheses about the respone of Q. ilex to climate change.     

基于FvCB模型分析盐分胁迫对棉花叶片光合作用的影响

为深入理解叶片光合特性对盐胁迫的响应机理,以棉花为试验材料,设置5个盐分(NaCl)浓度处理:0(CK)、50、100、150和200 mmol·L^-1,利用FvCB模型分析盐胁迫对棉花幼苗叶片光合特性的影响。结果表明:与CK相比,50和100 mmol·L^-1盐分处理增加了棉花叶片的最大羧化速率(V_{c max})和最大电子传递速率(J_max),但150和200 mmol·L^-1盐分处理显著降低了V_{c max}和J_max。叶片净光合速率(P_n)、叶肉导度(g_m)和暗呼吸速率(R_d)随盐分浓度升高而下降;与CK相比,50和100 mmol·L^-1盐分处理对g_m无显著影响,但P_n和R_d显著降低。150和200 mmol·L^-1盐分处理明显降低了P_n、g_m和R_d,且与0、50和100 mmol·L^-1盐分处理间存在显著差异;利用FvCB模型模拟了不同盐分胁迫下叶片净光合速率。与不考虑g_m的模拟结果相比,考虑g_m提高模拟值和实测值间的决定系数,并降低了平均绝对误差。棉花幼苗耐盐阈值为100～150 mmol·L^-1,随盐分浓度的增加,光合限制因素由叶肉因素转变为光合机构受损;引入g_m可以提高FvCB模型的模拟精度。     

澳门城市栖息地斑块中鸟类群落功能和谱系多样性

了解群落构建过程是生态学的核心和基本问题,这对于解释物种共存和物种多样性的维持,完善生物多样性保护政策至关重要。与传统的物种多样性相比,功能和谱系多样性能够提供更多的信息,特别是在群落构建过程方面提供深刻见解。2014年5月—2017年1月,采用样线法对澳门地区5个城市栖息地斑块中(生态一区、鹭鸟林、赛马场滩涂、关闸口岸滩涂和莲花桥侧红树林)的鸟类进行繁殖季和越冬季的调查,共调查14次。利用鸟类丰富度和多度来表征群落的物种多样性,其中多度以最大值保留法计;功能和谱系多样性分别采用功能丰富度(functional richness:FRic)和Faith'PD。同时,利用基于多度加权的平均成对功能距离(mean pairwise functional distance,MFD)和平均成对谱系距离(mean pairwise phylogenetic distance,MPD)来表征群落的功能和谱系结构。结果表明:共记录98种鸟类,隶属于14目32科,目、科、种中数量最多的依次为,雀形目鸟类最多为47种,鹭科物种数为11种,白鹭多度为849只;鸟类物种丰富度(68种)和PD在生态一区最高,多度在莲花桥侧红树林最高为2940只,MFD和FRic在赛马场滩涂最高,MPD在生态一区最高;斑块面积在鸟类丰富度、多度、FRic和PD中具有普遍重要性,植被面积和滩涂面积则分别强烈影响着MFD和MPD;关闸口岸滩涂和莲花桥侧红树林的鸟类群落SES.MFD显著低于随机值(P <0. 05),鹭鸟林和赛马场滩涂的鸟类群落SES. MPD显著低于随机值(P<0.05),表明关闸口岸滩涂和莲花桥侧红树林鸟类群落功能聚集(functional clustering),可能与生境过滤驱动群落构建有关。栖息地斑块的特征差异导致了鸟类群落构建机制的不同,这是仅仅考虑物种多样性难以提供的信息,说明了研究群落构建机制时考虑多维度多样性的必要性。     

Novel mannose-sequestration technique reveals variation in subcellular orthophosphate pools do not explain the effects of phosphorus nutrition on photosynthesis in Eucalyptus globulus seedlings

Although only a small proportion of plant phosphorus (P) is used for photosynthesis, the relationships between P and photosynthesis can be strong. It was hypothesized, in this study, that variation in the allocation of orthophosphate (Pi) between active (cytoplasmic) and nonactive (vacuolar) pools would underpin differences in rates of photosynthesis in 4-month-old Eucalyptus globulus seedlings grown with a varying P supply. Photosynthetic biochemistry was assessed by the response of net photosynthesis to increasing intercellular [CO2]. Cytoplasmic Pi was sequestered as mannose 6-phosphate. Total P and the proportion of P as Pi were positively related to P supply. The ratios of active : stored Pi (10-24%) varied little over the range of treatments. Active Pi was positively related to P supply, as was photosynthesis (7 micromol CO2 m(-2) s(-1) with 0 mM P vs. 16 micromol CO2 m(-2) s(-1) with 0.32 mM P). Positive relationships between P supply and photosynthesis were explained best by leaf P content, not by active pools of Pi. The distribution of Pi between the vacuole and the cytoplasm had little impact on the photosynthetic phosphorus-use efficiency (PPUE), and reductions in cytoplasmic Pi had little effect on photosynthesis. Hence, PPUE is an unsuitable guide for assessing plant responses to increasingly unavailable P in the environment.     

Inconsistency of the maximum parsimony method when the rate of nucleotide substitution is constant

The inconsistency of the maximum parsimony method is known to occur even when the rate of nucleotide substitution is constant. To understand why this inconsistency occurs, a mathematical study was conducted for the cases of five, six, and seven sequences. The results obtained indicate that this inconsistency occurs because the probability of occurrence of nucleotide configurations generated by one substitution on a short interior branch is often lower than that of configurations generated by more substitutions on other longer branches. The chance of occurrence of this event—or, the inconsistency of the maximum parsimony method—apparently increases as the number of sequences increases. The inconsistency may occur even when the extent of sequence divergence is relatively small. Correspondence to: M. Nei     

A general equation for the evaluation of the error that affects the value of the maximum specific growth rate

A general equation is proposed to evaluate the absolute error that affects the maximum specific growth rate calculated from batch or continuous experiments. This error depends on the relative errors of the cell concentration measurements and on the duration of the test.Nomenclature X ₁ Cell concentration at the beginning of the exponential growth phase or of the washing-out period - X ₁ Lowest value of X ₁ due to experimental errors - X ₁ Highest value of X ₁ due to experimental errors - X ₂ Cell concentration at the end of the exponential growth phse or of the washing-out period - X ₂ Lowest value of X ₂ due to experimental errors - X ₂ Highest value of X ₂ due to experiment errors - Relative error that affects X ₁ - Relative error that affects X ₂ - t Exponential growth stage or washing-out duration - Asolute error that affects - Maximum specific growth rate - ₁ Lowest value of due to experimental errors - ₂ Highest value of due to experimental errors The author is with the Instituto Mauá de Technologia, Estrada das Lágrimas 2035, 09580-900, São Caetano do Sul, SP, Brazil     

Robustness of coalescent estimators to between-lineage mutation rate variation

Data from HIV and from human neoplastic cells can show substantial between-lineage mutation rate variation even within a single population. Such variation may affect estimators of population quantities such as Theta = 4N(e)mu. Using simulated DNA data, I measured the effect of rate variation on recovery of Theta by the summary-statistic estimator of Watterson (Watterson GA. 1975. On the number of segregating sites in genetical systems without recombination. Theor Popul Biol. 7:256-276) and the coalescent maximum likelihood algorithm LAMARC (Kuhner MK. 2006. LAMARC 2.0: maximum likelihood and Bayesian estimation of population parameters. Bioinformatics. Advance Access doi: 10.1093/bioinformatics/btk051). Watterson's estimator showed a downward bias, as expected, with high values of Theta. LAMARC's mean estimate was accurate for all tested values of Theta and rate variation except for a downward bias when rate variation was maximal (i.e., the slow rate was zero). LAMARC had consistently narrower confidence intervals (CIs) than Watterson's estimator. Both methods tended to reject the truth too often when rate variation was 8x or greater and independent among branches, as well as when variation was 4x or greater and correlated among branches. In the case of Watterson's estimate, this excess rejection was fully attributable to variation among genealogies in the amount of total branch length associated with the fast and slow rates. However, in the case of LAMARC, some excess rejection was still observed even when between-genealogy variation was taken into account. Both estimators are robust to modest rate variation; however, their use should be coupled with a statistical test to rule out extreme rate variation as the resulting CIs may not be reliable.     

不同立地条件罗汉果组培苗的光合特性

比较了三种不同立地条件罗汉果组培苗的光合光响应特性以及主要环境因子和光合生理参数的日变化,从光合作用的角度探讨影响罗汉果组培苗生长的关健生态因子。结果显示:罗汉果组培苗的光饱和点和补偿点均随海拔的增高而增大;丘陵的最大净光合速率最高,山地最低。丘陵和山地罗汉果组培苗的净光合速率(Pn)日变化曲线呈"双峰"型,在12:30～13:30时出现轻微的非气孔限制,平地受云层遮挡,无第二峰出现;9:00～15:30时之间的罗汉果组培苗Pn与气孔导度(Gs)正相关,而Pn和Gs均与光量子通量密度(PFD)、叶温(TL)和叶片内外水汽压差(VPD)负相关,并随TL和VPD的增大下降幅度更大。丘陵环境条件最适合罗汉果组培苗的生长,中午前后Pn的下降与此时的强光、高温和低湿度有关,是气孔限制和非气孔限制同时作用的结果。     

松花湖铜绿微囊藻无菌株和单藻株生长因素的研究

用毛细滴管洗净法从松花湖分离纯化出铜绿微囊藻(Microcystisaeruginosa)的单藻株和无菌株,研究了温度、照度、N、P、Fe各种因素对单藻株和无菌株生长的影响。结果表明,各种因素对单藻株和无菌株最大比增长率的影响差别不大,单藻株和无菌株分别在温度33℃,照度5000Lx(2000Lx)、NO3-N浓度1.2mg·L-1,PO43-P浓度0.06mg·L-1,柠檬酸铁铁浓度0.05mg·L-1(0.04mg·L-1)时,达到最大比增长率。在一定浓度范围内,随着N、P、Fe浓度的增加,单藻株比无菌株的最大增长量高得多,可见附着细菌的存在,能促进铜绿微囊藻的生长。从松花湖湖水中N、P和Fe含量以及温度和照度的情况看,松花湖的某些区域已经基本具备了水华发生的条件。     

Maximum Likelihood Estimation of the Mortality Rate Function

Maximum likelihood estimator is obtained for the mortality rate function of a specific type appearing in survival data analysis. Strict consistency of this estimator is proved.     

横断山脉大绒鼠最大代谢率的季节性差异

最大代谢率对于动物的生存、繁殖和分布具有关键作用。实验用开放式呼吸仪测定了大绒鼠(Eothenomys miletus)夏季和冬季的冷诱导最大代谢率和运动最大代谢率。大绒鼠夏季的冷诱导最大代谢率O2为(7.24±0.61)ml/(g.h),运动最大代谢率O2为(7.69±0.59)ml/(g.h);冬季的冷诱导最大代谢率O2为(8.61±0.42)ml/(g.h),运动最大代谢率O2为(7.51±0.51)ml/(g.h)。冷诱导最大代谢率冬夏之间具有差异显著,而运动最大代谢率则差异不显著。结果表明:栖息于横断山脉的大绒鼠由于受到低温的胁迫,导致其冷诱导最大代谢率季节性变化较大,而运动最大代谢率则相对稳定。     

植物叶片最大羧化速率及其对环境因子响应的研究进展

植物叶片最大羧化速率对环境因子的响应关系是陆地生态系统生产力与碳收支研究的重要方面。论文从测定方法、影响因子与模拟模型3方面综述了植物叶片最大羧化速率及其对环境因子响应研究的最新进展,指出现有的植物叶片最大羧化速率对单个环境因子的响应研究严重制约着陆地生态系统生产力的准确评估。为弄清植物叶片最大羧化速率对环境因子的综合响应关系,迫切需要加强以下研究:(1)植物叶片最大羧化速率的生物与环境控制机制研究;(2)生物与环境因子协同作用下的植物叶片最大羧化速率定量模拟及其尺度化研究;(3)植物叶片最大羧化速率的环境因子阈值研究。     

Locomotor activity of mice divergently selected for basal metabolic rate: a test of hypotheses on the evolution of endothermy

The aerobic capacity model postulates that high basal metabolic rates (BMR) underlying endothermy evolved as a correlated response to the selection on maximal levels of oxygen consumption () associated with locomotor activity. The recent assimilation capacity model specifically assumes that high BMR evolved as a by‐product of the selection for effective parental care, which required long‐term locomotor activity fuelled by energy assimilated from food. To test both models, we compared metabolic and behavioural correlates in males of laboratory mice divergently selected on body mass‐corrected BMR. elicited by running on the treadmill did not differ between selection lines, which points to the lack of genetic correlation between BMR and . In contrast, there was a positive, genetic correlation between spontaneous long‐term locomotor activity, food intake and BMR. Our results therefore corroborate predictions of the assimilation capacity model of endothermy evolution.