氮输入对植物光合固碳的影响研究进展

植物光合固碳(C)是生物固C的重要途径和生态系统C循环中的重要环节。在全球环境变化背景下,研究氮(N)输入对植物光合固C的影响,对于更好的认识C、N循环过程及生态系统对全球变化的响应过程等具有重要意义。N输入是否能够增加植物固C取决于生态系统类型以及生态系统的N饱和度;草原和湿地生态系统N输入的临界负荷值较高,干旱、半干旱荒漠地区较低;N输入可能改变植物光合固C在各器官的分配,主要由植物生理、自身生长节律和环境养分等决定。由于物种和生态系统类型的差异,N输入对植物固C的影响仍具有很大的不确定性,目前缺乏准确、定量表达N输入对生态系统光合和C同化物分配影响的数学表达方法和过程算法。未来应着重加强N输入下C同化物分配的生物地球化学模型和N、P富集下植物光合固C耦合模型研究,并应用同位素标记和分子生物学技术,从生态系统角度综合探讨N输入下植物光合固C的分配和转化特征。     

营养生长期植物冠根比及其对环境因子的响应

将光强、温度和土壤水势等环境因子对植物光合、呼吸、同化物运输及生长等生理过程的影响结合起来,并考虑到各生理过程之间的交互作用,建立了一个营养生长期内植物条根比变化及对环境因子综合响应的模型。模型的运行结果表明,该模型与许多实验现象均相吻合。     

植物光合产物分配及其影响因子研究进展

植物光合产物分配受环境因子和生物因子的共同影响。为增进对植物对全球变化响应的理解, 从植物个体水平与群落/生态系统水平综述了植物光合产物分配的影响因子与影响机理的最新研究进展。植物个体在光照增强及受水分和养分胁迫时, 会将光合产物更多地分配到根系; CO₂浓度升高对植物光合产物分配的影响受土壤氮素的制约, 植物受氮素胁迫时, CO₂浓度升高会促进光合产物更多地分配到根系; 反之, 对植物光合产物分配没有影响。植物群落/生态系统的光合产物分配对环境因子的响应不敏感; 光合产物向根系的分配比例随其生长阶段逐渐降低。功能平衡假说、源汇关系假说和相关生长关系假说分别从环境因子、个体发育和环境因子与个体发育协同作用方面阐述了植物光合产物分配的影响机理。在此基础上,指出了未来拟重点加强的研究方向: 1)生态系统尺度的光合产物向呼吸部分的分配研究; 2)地下净初级生产力(belowground net primary productivity, BNPP)研究; 3)温室和野外条件下及幼苗和成熟林光合产物分配对环境因子响应的比较研究; 4)生态系统尺度的多因子控制试验; 5)整合环境因子和个体发育对植物光合产物分配格局的影响研究。     

磷影响陆地生态系统碳循环过程及模型表达方法

全球气候变暖已大大改变了陆地植物碳吸收能力, 提高了全球植被净初级生产力。随着气候变暖的加剧, 磷对植物生长的限制作用逐渐显现且不断增强, 磷影响陆地生态系统碳循环的机理和模型研究已成为研究热点。该文系统分析了磷影响陆地生态系统碳循环的相关机理以及模型对相关过程的定量化表达方法。综合对比分析了国际上的Carnegie- Ames-Stanford Approach-CNP (CASA-CNP)、Community Land Model-CNP (CLM-CNP)和Jena Scheme for Biosphere-Atmosphere Coupling in Hamburg-CNP (JSBACH-CNP)等碳、氮、磷耦合模型中磷影响植物光合作用与同化物分配过程、植物对磷的吸收过程、土壤中磷的转化过程以及生态系统磷输入与输出等过程的相关数学表达方法, 指出了模型算法的局限与不确定性以及未来模型发展与改进的方向。同时综合对比分析了CASA-CNP、CLM-CNP、JSBACH-CNP模型的基本特征, 总结了磷循环模型的建模方法, 为未来开展磷影响陆地生态系统碳循环的模型模拟研究提供了借鉴方法与参考思路。     

磷影响陆地生态系统碳循环过程及模型表达方法

全球气候变暖已大大改变了陆地植物碳吸收能力,提高了全球植被净初级生产力。随着气候变暖的加剧,磷对植物生长的限制作用逐渐显现且不断增强,磷影响陆地生态系统碳循环的机理和模型研究已成为研究热点。该文系统分析了磷影响陆地生态系统碳循环的相关机理以及模型对相关过程的定量化表达方法。综合对比分析了国际上的CarnegieAmes-Stanford Approach-CNP (CASA-CNP)、Community Land Model-CNP (CLM-CNP)和Jena Scheme for Biosphere-Atmosphere Coupling in Hamburg-CNP (JSBACH-CNP)等碳、氮、磷耦合模型中磷影响植物光合作用与同化物分配过程、植物对磷的吸收过程、土壤中磷的转化过程以及生态系统磷输入与输出等过程的相关数学表达方法,指出了模型算法的局限与不确定性以及未来模型发展与改进的方向。同时综合对比分析了CASA-CNP、CLM-CNP、JSBACH-CNP模型的基本特征,总结了磷循环模型的建模方法,为未来开展磷影响陆地生态系统碳循环的模型模拟研究提供了借鉴方法与参考思路。     

基于源库生长单位的温室番茄干物质生产-分配模拟

为了量化研究温室番茄果穗间干物质的分配,提高温室番茄栽培的效益,采用源库生长单位的测定方法,将经典的单叶同化物生产模型与GreenLab模型相结合,构建了干物质向源库生长单位内茎节、叶片、果实分配的动态模型,利用越冬茬、早春茬和春夏茬温室番茄各器官的干物质测定数据对模型进行了验证.结果表明:所构建的模型模拟结果与实测结果吻合性较好,不同茬口同化物生产模拟值与实测值的回归方程斜率为0.93,R~2为0.92;源库生长单位内茎节、叶片、果实以及根系的模拟值与实测值间回归方程斜率在0.85～0.89之间,其相对误差(R_e)均值分别为5.3%、5.6%、8.1%和3.6%,说明模型的模拟准确度较高,可为不同茬口温室番茄栽培管理提供理论依据和决策支持.     

植物营养生长期同化物分配的机理模型

将营养生长期的植株分为叶、茎、根三部分,在同化物供应条件下,将根系吸水能力与叶片蒸腾特性结合起来,以各器官之间的功能平衡为约束条件,得出了同化产物在各器官中的分配模型,该模型能够解释地上部分与地下部分生长的相互关系,能够解释环境因子对同化物分配的影响。利用Ｎａｇａｒａｊａｈ（１９８３）的实验资料对模型进行了验证,结果表明,此模型能较好地模拟它的实验结果。     

土壤干旱胁迫对作物影响的模拟研究进展

用于模拟土壤干旱胁迫对作物影响的模型分为两类,一是水分管理模型,此类模型并不模拟作物的生长发育,但可以用于灌溉管理;二是作物生长模拟模型,这类模型模拟作物生长的主要过程(如叶片生长、生物量的积累与分配等),通常以实际蒸腾与潜在蒸腾的比值估算土壤干旱胁迫对作物光合的影响,近年来发展的耦合模型将植物的碳同化、蒸腾、能量平衡以及气孔行为相耦合,使得土壤干旱胁迫对作物影响的模拟更具机理性。本文从不同模型模拟土壤干旱对作物影响的原理入手,阐述了水分管理模型(FAO水分生产函数模型)、作物生长模型(Aqua Crop模型、CERES-Maize模型、WOFOST模型、EPICphase模型、耦合模型)等具有代表性模型是如何模拟土壤干旱胁迫对作物生长发育和(或)产量影响的,提出了作物模型模拟土壤干旱胁迫影响时应着力解决的问题:完善干旱对作物物候的影响模拟;考虑花期不遇对作物产量影响的模拟;考虑后续持续影响的模拟机制;发展更加基于物理和生理过程的模型。提出:作物模型的发展还需要多领域如模型程序员、田间试验、植物生理学家的相互协同与发展,田间试验研究是作物模型发展不可或缺的数据来源与坚实基础。     

高等植物光合同化物的运输与分配

高等植物光合同化物的运输受维管束发育状况影响较大,有时会限制产量。而同化物在各库器官间的分配主要决定于库本身的特性,它常用库强度和优先权来描述。库强度是库容量和库活力的乘积,库容量用细胞数目来度量,而库活力常用相对生长速度来度量。近年来人们也用酶少戌一来度量库活力或库强度。而库的优先权描述的是各库器官需求同化物的优先次序,种子被认为是优等权最高的库。同化物的运输分配不仅决定于植物本身源、流、库的特     

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。     

Carbon partitioning in forage crops

The paper describes the conceptual models used to understand the processes determining plant growth rates in response to environmental changes. A series of experiments and growth models were used at three organizational levels: the specific plant organs, the whole plant and the plant canopy. The energy conversion efficiency and the total plant carbon balance were first examined. The carbon partitioning amongst the plant parts was then studied. The energy conversion efficiency is generally understood. In modelling carbon partitioning it was first necessary to establish the carbon demand for each plant organ. The carbon partitioned amongst plant organs was then calculated in two ways. The first one based on empirical data consisted in defining which organ received the carbon prior to other organs. The second one was based on the relationship between the carbon mass of specific organs and their trophic activity. This hypothesis allowed the optimization of the carbon partitioning in order to maximize the whole plant growth rate. The opportunities to use these theoretical approaches in plant growth modelling are discussed.     

基于植株拓扑结构的生物量分配的玉米虚拟模型

依据植物结构—功能相互作用机理,建立了能模拟玉米生长发育与形态结构建成的虚拟模型。该模型的重要部分为基于植株拓扑结构的生物量分配模块。叙述了该模块的构建原理,以2000年田间试验数据提取了玉米的发育、生物量生产和生物量分配参数。模型模拟了2001年的玉米生长发育与生物量分配过程,模拟结果与田间试验结果比较吻合。应用该模型模拟了2001年玉米不同生育阶段植株的生物量分配和各器官生物量积累动态。     

Carbon allocation in fruit trees: from theory to modelling

Carbon allocation within a plant depends on complex rules linking source organs (mainly shoots) and sink organs (mainly roots and fruits). The complexity of these rules comes from both regulations and interactions between various plant processes involving carbon. This paper presents these regulations and interactions, and analyses how agricultural management can influence them. Ecophysiological models of carbon production and allocation are good tools for such analyses. The fundamental bases of these models are first presented, focusing on their underlying processes and concepts. Different approaches are used for modelling carbon economy. They are classified as empirical, teleonomic, driven by source–sink relationships, or based on transport and chemical/biochemical conversion concepts. These four approaches are presented with a particular emphasis on the regulations and interactions between organs and between processes. The role of plant architecture in carbon partitioning is also discussed and the interest of coupling plant architecture models with carbon allocation models is highlighted. As an illustration of carbon allocation models, a model developed for peach trees, describing carbon transfer within the plant, and based on source–sink and Münch transport theory is presented and used for analyzing the link between roots, shoots and reproductive compartments. On this basis, the consequences of fruit load or plant pruning on fruit and vegetative growth can be evaluated.     

A Simulation Model for Dry Matter Partitioning in Cucumber

A dynamic model is developed for the simulation of the dailydry matter distribution between the generative and vegetativeplant parts and the distribution among individual fruits ingreenhouse cucumber. The model is based on the hypothesis thatdry matter partitioning is regulated by the sink strengths ofthe plant organs. The sink strength of an organ is defined hereas its potential growth rate, i.e. the growth rate at non-limitingassimilate supply. The sink strength of each individual fruitis described as a function of its temperature sum after anthesisand the actual temperature, that of the vegetative plant partsas a function of actual temperature only. The formation rateof non-aborting fruits is essentially a function of the source/sinkratio. Model results agreed well with the measured fluctuating distributionof dry matter between fruits and vegetative parts. The measuredeffects of three intensities of fruit removal were also simulatedsatisfactorily. When simulating the partitioning among individualfruits the final fruit size was simulated quite well. However,the growth rate of young fruits was usually overestimated andthat of old fruits underestimated, because of dominance amongfruits. This phenomenon could be accounted for by incorporatingpriority functions into the model. Finally, a sensitivity analysisof the model was performed to investigate the effects of someclimatic factors, manipulations of the number of fruits on aplant and model parameters on dry matter distribution. Strategiesto manipulate the dry matter distribution are discussed.Copyright1994, 1999 Academic Press Cucumber, Cucumis sativus (L.), dry matter distribution, fruit growth, partitioning, simulation model, source-sink     

Combined MRI–PET dissects dynamic changes in plant structures and functions

Unravelling the factors determining the allocation of carbon to various plant organs is one of the great challenges of modern plant biology. Studying allocation under close to natural conditions requires non-invasive methods, which are now becoming available for measuring plants on a par with those developed for humans. By combining magnetic resonance imaging (MRI) and positron emission tomography (PET), we investigated three contrasting root/shoot systems growing in sand or soil, with respect to their structures, transport routes and the translocation dynamics of recently fixed photoassimilates labelled with the short-lived radioactive carbon isotope ¹¹C. Storage organs of sugar beet ( Beta vulgaris ) and radish plants ( Raphanus sativus ) were assessed using MRI, providing images of the internal structures of the organs with high spatial resolution, and while species-specific transport sectoralities, properties of assimilate allocation and unloading characteristics were measured using PET. Growth and carbon allocation within complex root systems were monitored in maize plants ( Zea mays ), and the results may be used to identify factors affecting root growth in natural substrates or in competition with roots of other plants. MRI–PET co-registration opens the door for non-invasive analysis of plant structures and transport processes that may change in response to genomic, developmental or environmental challenges. It is our aim to make the methods applicable for quantitative analyses of plant traits in phenotyping as well as in understanding the dynamics of key processes that are essential to plant performance.     

Nitrogen Uptake and Plant Growth II. An Empirical Model of Vegetative Growth and Partitioning

An empirical model of vegetative plant growth is presented.The model is based on experimental data on Polygonum cuspidatum,which showed (1) that the partitioning of dry matter and nitrogenamong organs was linearly related to the nitrogen concentrationof the whole plant and (2) that leaf thickness was negativelycorrelated with leaf nitrogen concentration. The model properlydescribes the behaviour of plants. Steady-state solutions ofthe model give the relative growth rate, specific leaf weight,and partitioning of dry matter and nitrogen among organs withthe net assimilation rate and the specific absorption rate asenvironmental variables. The effect of nitrogen removal on drymatter and nitrogen partitioning was examined as non-steady-statedynamic solutions of the model. The model predicted not onlyreduced leaf growth and enhanced root growth but also a fluxof nitrogen from the leaf to the root, which agreed with theexperimental results. Mathematical model, partitioning of dry matter and nitrogen, plant nitrogen, relative growth rate, shoot: root ratio, specific leaf weight     

Effects of foliar applied gibberellic acid and benzyladenine upon yield components in sunflower (Helianthus annuus L.)

Sunflower yield is determined by seed number/m^–2 and by achene weight. Frequently, a high percentage of empty achenes in the inner portion of the capitulum, probably due to a reduced vascularization of that section of the flower head, decreases final yield. The objective of the present research is to determine if foliarly applied gibberellic acid (GA) and benzyladenine (BA) can enhance the vascularization in the inner portion of the capitulum, improving photoassimilate translocation. Field experiments were conducted during 1989/90 with hybrid SPS 894 and during 1990/91 with hybrid ACA 882. GA (150 mg/l^–1), BA (150 and 250 mg/l^–1) and GA 150+BA 150 mg/l^–1 each were foliarly applied 20, 40, or 60 days after emergence. For both seasons and hybrids plant growth regulator (PGRs) applications significantly reduced the percentage of empty achenes, increased achene weight, achene weight (× 1000) and achene number in the inner portion of the capitulum and in the middle and outer portion during 1990/91. A 25% increase in seed yield was achieved due to PGR application and the capitulum partition index (achene weight/receptacle weight^–1, CPI) was significantly increased due to an improvement in photoassimilate distribution. A distribution model was derived showing that preferential allocation of photoassimilates in the outer portion of the capitulum can be modified by PGR application, demonstrating that photoassimilate distribution is under hormonal control.Consejo Nacional de Investigaciones Científicas y Tecnológicas (CONICET)     

Regulation of photosynthetic carbon metabolism in cucumber by light intensity and photosynthetic period

The effects of photosynthetic periods and light intensity on cucumber (Cucumis sativus L.) carbon exchange rates and photoassimilate partitioning were determined in relation to the activities of galactinol synthase and sucrose-phosphate synthase. Carbon assimilation and partitioning appeared to be controlled by different mechanisms. Carbon exchange rates were influenced by total photon flux density, but were nearly constant over the entire photoperiod for given photoperiod lengths. Length of the photosynthetic periods did influence photoassimilate partitioning. Assimilate export rate was decreased by more than 60% during the latter part of the short photoperiod treatment. This decrease in export rate was associated with a sharp increase in leaf starch acccumulation rate. Results were consistent with the hypothesis that starch accumulation occurs at the expense of export under short photoperiods. Galactinol synthase activities did not appear to influence the partitioning of photoassimilates between starch and transport carbohydrates. Sucrose phosphate synthase activities correlated highly with sugar formation rates (sucrose, raffinose, stachyose + assimilate export rate, r = 0.93, α = 0.007). Cucumber leaf sucrose phosphate synthase fluctuated diurnally in a similar pattern to that observed in vegetative soybean plants.