水稻光合生产与干物质累积的动态模拟

在综合已有研究成果的基础上,兼顾模型的机理性与实用性的平衡,构建了水稻光合生产与干物质累积的模拟模型．模型采用高斯积分法有效地计算冠层每日的总光合量,并考虑了冠层消光系数随生理发育时间（PDT)的动态变化,模型较充分地量化了生理年龄、温度、叶片含氮量及水分亏缺因子等对光合作用的影响及维持呼吸系数与PDT的动态变化关系、利用独立的试验资料对模型核实的结果显示,模型可以较好地预测不同生长条件下的生物量累积动态,具有较强的机理性与实用性．     

额济纳荒漠河岸胡杨林叶片气孔导度与微环境因子关系的模拟研究

以额济纳荒漠河岸胡杨(Populus euphratica)为研究对象,利用LI-6400光合测定仪于2005年5~9月份观测了胡杨叶片气体交换数据,研究了胡杨叶片气孔导度与光合速率、光合有效辐射与光合速率之间的关系.结果表明:(1)胡杨叶片净光合速率随气孔导度的增大而升高,但当气孔导度增加到一定值后,光合速率的增加变缓慢直至平稳,并主要是非气孔限制因素造成的;Ball-Berry模型(B-B模型)能够很好地描述气孔导度与光合速率之间的关系(R2=0.92).(2)叶片净光合速率随着有效辐射的变化符合非直角双曲线规律(R2=0.99).(3)B-B模型和非直角双曲线光合模型耦合后模拟值与观测值之间存在很好的正相关性(r=0.93),但耦合模型的模拟值还是较实测值偏大.因此,在干旱区还必须考虑水分限制因素对气孔开闭的控制作用,进一步构建适合干旱区生态系统特点的水-碳耦合循环机理模型.     

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.     

水分限制条件下小麦碳同化作用和生物量累积的简单机理模型

以辐射和日长作为自变量,首先建立了一个春小麦碳同化作用和生物量累积过程的简单机理模型;再以叶片水势作为小麦受水分限制的指标,考虑了水分限制下光能利用率、碳同化导度等均受抑制的设定,完成了水分限制下小麦碳同化作用和生物量累积过程简化机理模型的构建。通过分析和田;司实验数据的对比,表明该简单机理模型能很好地反映小麦在有水分限制和无水分限制条件下的碳同化作用和生物量的累积过程。     

臭氧胁迫下冬小麦物质生产与分配的数值模拟

利用ML9810B型臭氧监测分析仪,测定了浙江嘉兴麦田空气O3浓度,并通过改进的开顶式气室实验确定O3浓度变化对冬小麦叶片光合速率的影响函数.在此基础上,加入O3对叶片生长和穗部光合影响的模拟函数,建立反映O3对冬小麦生长和产量形成影响的作物模型.模型的检验结果表明,该模型较好地反映了O3对冬小麦生长的影响,生物量平均相对误差为10.3%.对冬小麦春后生育期(3—5月)的研究表明,水肥适宜时,由O3影响造成的该地区冬小麦干物质累积总损失量为11.4%,产量损失为17.8%.     

小兴安岭低山区红松生长的气候响应机制

基于小兴安岭红松的树轮资料,确定了Tree-Ring生态机理模型模拟红松树木生长的参数.应用Tree-Ring模型对小兴安岭红松的生长过程进行了模拟,结果显示Tree-Ring模型在该地具有较好的适用性.参数敏感性分析表明红松树木生长比较敏感的参数是光合最低温度、光合最适温度下限、最适土壤体积含水率上限和最大土壤体积含水率.模拟发现,红松树轮宽度变化主要受到生长季上一年10月份气温和当年4月份气温变化控制.形成层开始生长平均是在4月下旬,这时水分充足,而温度在光合最低温度和最适温度下限之间,温度愈高,光合速率愈大,储存的养料愈多,因此表现为与树轮宽度的正相关关系.形成层生长结束的时间平均在10月上旬,用于形成层细胞生长的光合产物的消耗减少,而光合速率随着温度的升高而增大,因此,10月份的气温越高为下一年储存的养料越多,翌年易形成宽轮.     

水分胁迫对短枝型果树光合作用的非气孔限制

水分胁迫使叶片相对含水量降低,气孔阻力增大.水分胁迫光合速率的下降除受气孔因素影响之外,随着胁迫时间的延长和胁迫程度的加剧,水分胁迫导致O-·2累积,H2O2含量增加,从而引发膜脂过氧化,造成膜渗漏,质膜相对膜透性增大,膜脂过氧化产物MDA含量升高,由膜系统破坏而诱发的非气孔因素成为光合速率下降的主要原因.     

小麦和玉米叶片光合-蒸腾日变化耦合机理

植物叶片光合-蒸腾耦合是陆地生态系统碳-水耦合的基础.已有研究将叶片光合-蒸腾耦合笼统归因于气孔的共同控制作用,缺乏对其耦合机理的全面分析.选择华北地区大田作物冬小麦(C3)和夏玉米(C4)为研究对象,分别在小麦开花期和玉米拔节期选择典型晴天进行叶片光合蒸腾日变化观测(8:00-18:00).结果发现:1)光合速率(An)、蒸腾速率(Tr)以及光合有效辐射(PAR)、叶片表面温度(T)和气孔导度(gs)均表现出单峰日变化特征,峰值出现在正午前后;2)An-Tr具有极显著线性正相关关系(小麦和玉米的相关系数分别为0.75**和0.92**,回归直线斜率分别为1.99和3.62);3)PAR、T和gs与An和Tr有线性正相关关系;4)PAR-An与PAR-Tr、T-An与T-Tr、gs-An与gs-Tr的回归直线形态非常相似.分析认为:1)在光合-蒸腾耦合特征方面,C3作物小麦和C4作物玉米叶片光合-蒸腾都有明显的线性耦合关系,但两者的耦合关系特征存在明显差异,玉米的An-Tr线性回归斜率要明显大于小麦;2)在光合-蒸腾耦合机理方面,日变化中PAR、T和gs同时受太阳辐射调控与An、Tr发生趋向相同、形态相似且近似同步的变化,因此PAR-An与PAR-Tr、T-An与T-Tr、gs-An与gs-Tr具有形态相似的线性关系,这保证了在PAR、T和gs等调控因子发生较大变化的日变化过程中光合-蒸腾保持良好的线性耦合关系.     

马铃薯生育期和干物质积累的动态模拟研究

根据三年的田间试验数据和有关气象资料,提出了马铃薯生育期和干物质积累的模拟模型、用高斯方程计算每天的温度条件对马铃薯生育期和干物质积累的生理效应,改进了前人的生育期模型和温度条件对干物质积累影响系数的计算方法．以每天的单位叶面积变化、群体上方的有效辐射和温度变化模拟群体的干物质积累、结果表明,本研究的模型有明确的机理性和较高的精度．用Visual Basic 6．0界面表达每日生态条件变化对群体光合生产和干物质积累的影响,模拟结果具有直观的机理性,从而克服了同类研究中的缺陷。     

水稻群体冠层光分布及光合作用模型

作物冠层光分布及光合作用模型,是作物栽培学、作物育种学研究的共同基础,对优化设计和评价作物株型、模拟作物生长发育与对环境变化的响应研究都有十分重要的价值.本文根据水稻群体冠层结构的特点,在虚拟切层法的基础上,建立了水稻群体冠层光分布及光合速率模型,模型包括冠层形态子模型、冠层光分布子模型和冠层光合速率子模型等.利用本模型,对设定的15625种水稻株型的光合速率进行了模拟计算,获得水稻最佳株型模型.结果表明,水稻群体光合速率与叶片数、叶含氮量、叶长、叶宽和叶倾角等5因素密切相关;最佳株型的上述5因素在冠层上部取值大,向下逐渐变小.     

Effect of light interception by non-photosynthetic organs on canopy photosynthetic production

A canopy photosynthesis model was derived on the assumption that the light diminution within a canopy is caused by both leaves and non-photosynthetic organs. The light diminution by leaves and that by non-photosynthetic organs were taken into account separately in the Lambert-Beer equation of light extinction. The light flux density on the leaf surface at each depth was evaluated from the leaf's share of light. The light flux density on the leaf surface thus obtained was incorporated into the Monsi-Saeki model of canopy photosynthesis. The proposed model was applied for estimating gross canopy photosynthesis in a 19-year-oldLarix leptolepis plantation where 38% of the light diminution was due to non-photosynthetic organs. The daily canopy photosynthesis on one summer day calculated using the present model was about 22% less than that calculated by the conventional Monsi-Saeki model, in which light interception by non-photosynthetic organs is neglected. The degree of such reduction in canopy photosynthesis through shading by non-photosynthetic organs was assessed in relation to parameters affecting light extinction, leaf photosynthetic characteristics, and light regime above the canopy.     

陆地碳循环研究中植物生理生态过程模拟进展

植物生理生态过程的模拟是陆地碳循环模型研究中的关键过程之一,就与碳循环过程密切相关的3个关键的植物生理生态过程;光合作用,碳分配和物候等过程的数学模式进行分类：（1）光合作用模式,根据光合作用模式基础的不同把光合作用模式分为：半经验模式;机理模式和使用卫星遥感资料的模式等;（2）植物碳分配模式介绍了功能平衡模式;运输-阻力模式;光合作用与生长模式;环境反应模式和大尺度生态系统模式等5类。（3）植被物候模式;根据观测和参数化方法的不同可以将现有的物候数值模式分为两类;观测统计模式和使用卫星遥感资料的物候模式,对各类模式的主要控制方程,研究进展和应用分别进行了简要评述。     

A Mathematical Model for Leaf Photosynthesis of Mulberry

A mathematical model of leaf photosynthesis has been established. In this model, the processes of photosynthesis are divided into two parts, ie., the carboxylation process driven by light which is dependent on temperature and CO2 concentration, and the diffusion of CO2 from atmosphere to the carboxylation site. Finatly, CO2 uptake by the leaf is understood as dependent on 1), the CO2 response curve of the leaf mesophyll and 2). the CO2 partial pressure in the intercellular space in leaf. The COs response curve of the leaf photosynthesis is described mathematically in terms of carboxylation efficiency (Ca) or its initial slope and the photosynthetic capacity (Pm) or the CO2-saturated uptake rate of CO2 uptake, and dark respiration (Rd). The dependency of photosynthesis on leaf temperature and incident light intensity is incorporated into variations of those parameters which establish an appropriate response to internal CO2 pressure for particular light and temperature conditions prevailing at any time. Secondly the interactiion of stomata with photosynthesis is represented as an empirical relation between stomatal conductance and a combined environmental physiological index, APn·Hx/CaThe parameters used in the modelwere estimated with Marquardt-Newton method for non-linear function. Field measurements of mulberry leaf photosynthesis provided a data set for model testing. The resuks show that the simulated values of the model agree well with observed data. The model was used to analyse the response surface of leaf conductance and photosynthesis to environmental factors—Applications and limitations of the model are discussed     

美国黑核桃实生苗单叶片光合作用生理生态模型的建立与验证

在对叶片光合过程机理分析的基础上,结合数学分析方法,建立了模拟美国黑核桃单叶片光合作用的机理模型,该模型包含了叶片光合作用的限速的生化过程和气孔调节因素,对光合作用一气孔导度的耦合模型进行了简化,使之既便于应用,又能较准确地反映田间条件下的情况,并就光合作用对环境因子(太阳辐射、温度及CO2浓度等）变化的响应特征及响应的合理性进行了分析,使用整个生长季实测的叶片生理数据及生态环境数据对所建模型进行了验证,结果表明,模型可以较准确地模拟田间美国黑核桃叶片的光合速率;确定了美国东部黑核桃、北加州黑核桃等两种黑核桃单叶片光合作用与环境因子互作的数量美系。     

Circadian rhythms have insignificant effects on plant gas exchange under field conditions

Circadian rhythms in photosynthesis and stomatal conductance have been widely observed, but their possible adaptive significance is unknown. To determine whether such rhythms have a significant effect on the daily courses of carbon gain and/or water loss under field conditions, we obtained laboratory data on circadian rhythms in gas exchange of Saururus cernuus L., a wetland perennial. Using these data we modified a widely used mathematical model of photosynthesis and stomatal conductance by introducing the observed circadian‐rhythmic variation into the maximum rates of electron transport and carboxylation. We measured photosynthesis and stomatal conductance hourly on the same species growing naturally in the field and compared measured daily courses of photosynthesis and stomatal conductance with daily courses calculated using the model as originally formulated and also as modified to include circadian rhythms. The model fit the field data only slightly better when rhythms were included: the rhythms accounted for only about 1% of the observed daily carbon gain. Thus, these rhythms probably do not affect photosynthesis and stomatal conductance in the field.     

Exploring the spatial distribution of light interception and photosynthesis of canopies by means of a functional-structural plant model

Background and Aims

At present most process-based models and the majority of three-dimensional models include simplifications of plant architecture that can compromise the accuracy of light interception simulations and, accordingly, canopy photosynthesis. The aim of this paper is to analyse canopy heterogeneity of an explicitly described tomato canopy in relation to temporal dynamics of horizontal and vertical light distribution and photosynthesis under direct- and diffuse-light conditions.

Methods

Detailed measurements of canopy architecture, light interception and leaf photosynthesis were carried out on a tomato crop. These data were used for the development and calibration of a functional–structural tomato model. The model consisted of an architectural static virtual plant coupled with a nested radiosity model for light calculations and a leaf photosynthesis module. Different scenarios of horizontal and vertical distribution of light interception, incident light and photosynthesis were investigated under diffuse and direct light conditions.

Key Results

Simulated light interception showed a good correspondence to the measured values. Explicitly described leaf angles resulted in higher light interception in the middle of the plant canopy compared with fixed and ellipsoidal leaf-angle distribution models, although the total light interception remained the same. The fraction of light intercepted at a north–south orientation of rows differed from east–west orientation by 10 % on winter and 23 % on summer days. The horizontal distribution of photosynthesis differed significantly between the top, middle and lower canopy layer. Taking into account the vertical variation of leaf photosynthetic parameters in the canopy, led to approx. 8 % increase on simulated canopy photosynthesis.

Conclusions

Leaf angles of heterogeneous canopies should be explicitly described as they have a big impact both on light distribution and photosynthesis. Especially, the vertical variation of photosynthesis in canopy is such that the experimental approach of photosynthesis measurements for model parameterization should be revised.     

A Dynamic Model for Photosynthesis

A dynamic mathematical model of the effect of radiant flux densityand CO₂ concentration on the rate of photosynthesis is proposed.An appropriate dynamic experimental method for ecological studiesof this subject is described. The methodology permits the analysisof numerous problems, including the effect of changes in CO₂concentration on photosynthesis and the effectiveness of energyconversion by a leaf of a plant in different environmental conditions. The dynamic model for photosynthesis is composed of two separateinteracting non-linear parts; one describes the dynamics ofthe complex set of light reactions, and the other describesthe dark reactions. The model explains the dynamics of leafphotosynthesis in a closed circuit flow system, and also explainsthe expressions for the equilibrium states of photosyntheticrate widely used in the literature. photosynthesis, mathematical model, carbon dioxide fixation, light reactions     

CO2浓度升高对大豆冠层光合速率影响的数值模拟研究

利用美国Li-6200光合测定系统对鲁豆4号叶片光合速率进行了大量测定研究,确定了大豆叶片光-光合作用模式,模式中考虑了CO2浓度对光合作用速率的影响,在此基础上进一步测定了大豆冠层结构,建立了一个大豆冠层光合速率数值模式.利用GXH-305红外线CO2分析仪外接50×50×120cm同化箱对冠层光合速率进行了实际测定,结果表明当CO2浓度低于660ppm时,模式可以较好地模拟出CO2浓度升高对群体光合速率的影响,平均相对误差为7.41%.本文所测得的大量实验数据,为研究CO2浓度升高对大豆生长影响提供了更加可靠的模型参数,同时也为进一步建立自然状况下大豆生长数值模式提供了一定的理论依据.     

Development of the Monsi-Saeki theory on canopy structure and function

BACKGROUND AND AIMS: Monsi and Saeki (1953) published the first mathematical model of canopy photosynthesis that was based on the light attenuation within a canopy and a light response of leaf photosynthesis. This paper reviews the evolution and development of their theory. SCOPE: Monsi and Saeki showed that under full light conditions, canopy photosynthesis is maximized at a high leaf area index (LAI, total leaf area per unit ground area) with vertically inclined leaves, while under low light conditions, it is at a low LAI with horizontal leaves. They suggested that actual plants develop a stand structure to maximize canopy photosynthesis. Combination of the Monsi-Saeki model with the cost-benefit hypothesis in resource use led to a new canopy photosynthesis model, where leaf nitrogen distribution and associated photosynthetic capacity were taken into account. The gradient of leaf nitrogen in a canopy was shown to be a direct response to the gradient of light. This response enables plants to use light and nitrogen efficiently, two resources whose supply is limited in the natural environment. CONCLUSION: The canopy photosynthesis model stimulated studies to scale-up from chloroplast biochemistry to canopy carbon gain and to analyse the resource-use strategy of species and individuals growing at different light and nitrogen availabilities. Canopy photosynthesis models are useful to analyse the size structure of populations in plant communities and to predict the structure and function of future terrestrial ecosystems.