黄土高原优势灌丛营养器官化学计量特征的环境分异和机制

为了探究黄土高原灌丛群落中优势物种的根、茎和叶等营养器官之间碳(C)、氮(N)、磷(P)及其比值等化学计量特征的环境分异性及其与土壤养分的耦合性, 在甘肃省和宁夏回族自治区境内的3个灌丛集中分布区(甘肃南部、宁夏北部和甘肃西部)沿水热梯度选取41个样点进行样地调查。结果显示: 1)甘肃、宁夏灌丛群落的有机物质含量及P资源相对匮乏, 而N资源相对丰富。2)从甘肃南部、宁夏北部到甘肃西部, 生长季温度递增、年降水量递减, 与此耦合, 土壤养分也逐级递减, 沿着土壤养分梯度, 黄土高原优势灌丛根、茎和叶的C、N、P储量减少, 根和茎的C:N下降, 根、茎和叶的N:P上升, 但在宁夏北部和甘肃西部间差异不显著。同时, 3个优势灌丛分布区的优势灌丛各器官间营养元素的分配格局不同。3)土壤养分相对较高的区域优势灌丛间各器官营养元素储量无差异, 而土壤养分较低区域亲缘关系较远的优势灌丛间各器官的营养元素储量差异显著, 而亲缘关系较近的优势灌丛各器官营养元素储量差异不显著。黄土高原优势灌丛各器官C、N、P化学计量特征是植物体与土壤中化学元素耦合的结果, 当土壤养分逐渐升高时, 植物体内的化学元素储量也逐渐增多。该研究不仅有助于认识黄土高原优势灌丛化学计量环境分异规律, 而且有助于洞察不同土壤条件下C、N、P在优势灌丛营养器官间的分配格局和植物资源分配策略, 并为黄土高原植被的管理和恢复提供一定的理论基础。     

On the botanic model of plant growth with intermediate vegetative-reproductive stage

The application of dynamic optimization to mathematical models of ontogenic biological growth has been the subject of much research [see e.g. . J. Theor. Biol. 33, 299-307]. Koz?owsky and Zió?ko [1988. Thor. Popul. Biol. 34, 118-129] and Zió?ko and Koz?owski [1995. IEEE Trans. Automat. Contr. 40(10), 1779-1783] presented a model with gradual transition from vegetative to reproductive growth. The central point of their model is a mixed state-control constraint on the rate of reproductive growth, which leads to a mixed vegetative-reproductive growth period. Their model is modified here in order to take into account the difference of photosynthesis use efficiency when energy is accumulated in the vegetative and in the reproductive organs of a plant, respectively. The simple assumption on correlation between photosynthesis and temperature permits us to modify the model in a form that is useful for changing climate. Unfortunately, the mathematical solution of the optimal control problem in Koz?owsky and Zió?ko (1988) and Zió?ko and Koz?owski (1995) is incorrect. The strict mathematical solution is presented here, the numerical example from is solved, and the results are compared. The influence of the length of the season and the relative photosynthesis use efficiency, as well as of the potential sink demand of the reproductive organs, on the location and duration of the mixed vegetative-reproduction period of growth is investigated numerically. The results show that the mixed growth period is increased and shifted toward the end of the season when the lengths of the season is increased. Additional details of the sensitivity analysis are also presented.     

Respiration and reproductive effort in Xanthium canadense

* BACKGROUND AND AIMS: The proportion of resources devoted to reproduction in the plant is called the reproductive effort (RE), which is most commonly expressed as the proportion of reproductive biomass to total plant biomass production (RE(W)). Reproductive yield is the outcome of photosynthates allocated to reproductive structures minus subsequent respiratory consumption for construction and maintenance of reproductive structures. Thus, RE(W) can differ from RE in terms of photosynthates allocated to reproductive structures (RE(P)). * METHODS: Dry mass growth and respiration of vegetative and reproductive organs were measured in Xanthium canadense and the amount of photosynthates and its partitioning to dry mass growth and respiratory consumption were determined. Differences between RE(W) and RE(P) were analysed in terms of growth and maintenance respiration. * KEY RESULTS: The fraction of allocated photosynthates that was consumed by respiration was smaller in the reproductive organ than in the vegetative organs. Consequently, RE(P) was smaller than RE(W). The smaller respiratory consumption in the reproductive organ resulted from its shorter period of existence and a seasonal decline in temperature, as well as a slower rate of maintenance respiration, although the fraction of photosynthates consumed by growth respiration was larger than in the vegetative organs. * CONCLUSIONS: Reproductive effort in terms of photosynthates (RE(P)) was smaller than that in terms of biomass (RE(W)). This difference resulted from respiratory consumption for maintenance, which was far smaller in the reproductive organ than in vegetative organs.     

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     

Analysing growth and development of plants jointly using developmental growth stages

Background and Aims Plant growth, the increase of organ dimensions over time, and development, the change in plant structure, are often studied as two separate processes. However, there is structural and functional evidence that these two processes are strongly related. The aim of this study was to investigate the co-ordination between growth and development using mango trees, which have well-defined developmental stages.Methods Developmental stages, determined in an expert way, and organ sizes, determined from objective measurements, were collected during the vegetative growth and flowering phases of two cultivars of mango, Mangifera indica. For a given cultivar and growth unit type (either vegetative or flowering), a multistage model based on absolute growth rate sequences deduced from the measurements was first built, and then growth stages deduced from the model were compared with developmental stages.Key Results Strong matches were obtained between growth stages and developmental stages, leading to a consistent definition of integrative developmental growth stages. The growth stages highlighted growth asynchronisms between two topologically connected organs, namely the vegetative axis and its leaves.Conclusions Integrative developmental growth stages emphasize that developmental stages are closely related to organ growth rates. The results are discussed in terms of the possible physiological processes underlying these stages, including plant hydraulics, biomechanics and carbohydrate partitioning.     

Dry Matter Partitioning in Tomato: Validation of a Dynamic Simulation Model

A model for dynamic simulation of dry matter distribution betweenreproductive and vegetative plant parts and the distributionamong individual fruit trusses in glasshouse tomato, is validated.The model is part of the crop growth model TOMSIM and is basedon the hypothesis that dry matter distribution is regulatedby the sink strengths of the plant organs, quantified by theirpotential growth rates, i.e. the growth rates at non-limitingassimilate supply. Within the plant, individual fruit trussesare distinguished and sink strength of a truss is describedas a function of its development stage. Truss development rateis a function of temperature only. The same potential growthcurve, proportional to the number of fruits per truss, is adoptedfor all trusses. In a simple version of the model, vegetativeplant parts are lumped together as one sink with a constantsink strength. In a more detailed version, vegetative sink strengthis calculated as the sum of sink strengths of vegetative units(three leaves and stem internodes between two trusses). The model was validated for six glasshouse experiments, coveringeffects of planting date, plant density, number of fruits pertruss (pruning at anthesis), truss removal (every second trussremoved at anthesis), single- and double-shoot plants and atemperature experiment conducted in climate rooms at 17, 20or 23 °C. Daily increase in above-ground dry weight, averagedaily temperatures and number of set fruits per truss were inputsto the model. Both the simple and the more detailed model showedgood agreement between measured and simulated fraction of drymatter partitioned into the fruits over time. For the simpleversion of the model, the slope of the lines relating simulatedto measured fraction partitioned into the fruits (16 data sets),varied between 0.92 and 1.11, on average it was 1.04, implying4% over-estimation for this fraction. For the detailed modelthese numbers were slightly better: 0.89, 1.08 and 1.01, respectively.The temperature experiment revealed no important direct influenceof temperature on the ratio between generative and vegetativesink strength. Simulated truss growth curves showed reasonableagreement with the measurements, although both models over-estimated(17% on average) final dry weight of the lower trusses (truss1 –3) on a plant. Modelling dry matter partitioning basedon sink strengths of organs is promising, as it is a general,dynamic and flexible approach, showing good agreement betweenmeasurements and simulation for a range of conditions. Applicabilityof the model is, however, still limited as long as the numberof fruits per truss (flower and /or fruit abortion) is not simulated,as this is a major feedback mechanism in plant growth. Dry matter distribution; sink strength; glasshouse; model; partitioning; simulation; temperature; tomato; TOMSIM; validation     

Theory for growth of plants derived from the nitrogen productivity concept

A theory is developed on the assumption that growth of plants is determined by the current amount of nitrogen in the plants. The nitrogen-growth relation is formalized in the nitrogen productivity concept (amount of biomass produced per amount of nitrogen in the biomass and per unit of time), which is essentially a constant for a given species under fixed environmental conditions. A number of results follow for increases in whole plant biomass: (A) The relative growth rate is a linear function of the internal nitrogen concentration. (B) The maximal relative growth rate uniquely determines the scaling of the time axis. (C) Exponential growth is consistent only with stable internal nitrogen concentration. Dose-response curves expressed in reduced variables (the ratio between a variable and the same variable for a plant growing under optimal conditions) are universal, so that all species and all environmental conditions yield the same curve. This is confirmed by experimental data. The shape (linear, exponential, etc.) of the nitrogen uptake curve is the only parameter differentiating these universal curves. The Mitscherlich curve or variations of it can be fitted very closely to the derived dose-response curves, except under exponential growth. A conclusion drawn from the analysis is that the results of nutrition experiments cannot be properly interpreted unless the variation with time of the amount of nitrogen in the plant is known. The theory can be extended to more complex situations, for example, time-varying environmental conditions.     

Normalization and calculation of lanthanide element concentrations in environmental samples

Summary A mathematical model for the prediction of lanthanide element concentrations in soil and plant samples is presented. A comparison between pre dicted and measured lanthanide values in soil and plant samples show, that the model produces good results for the elements in the soil samples and for most elements in plant material. The accuracy of prediction worsens with decreasing concentration of the heavier lanthanide elements. The mathematical model presented is not valid on other environmental samples like aerosols, because no data for these matrices are available yet to calibrate our normalized curves.     

Analysis of the Time Course of Change in Nitrogen Content in Dactylis glomerata L. Using a Model of Plant Growth

The growth, root fraction and nitrogen content of Dactylis glomerataL. grown hydroponically in constant environmental conditions,were measured in the vegetative phase. The variation of theseparameters denotes a progressive change in the chemical compositionof the plant, which can be attributed to changing proportionsof structural material, which is immediately available for growth,and storage material. On the basis of a kinetic model of plantgrowth, a definition of the two components was proposaed, whichled us to derive a relationship between relative growth rateand nitrogen content. This relationship was found to be compatiblewith experimental data. Dactylis glomerata L., vegetative phase, kinetic model, growth rate, nitrogen content     

Auxin Depletion from the Leaf Axil Conditions Competence for Axillary Meristem Formation in Arabidopsis and Tomato

The enormous variation in architecture of flowering plants is based to a large extent on their ability to form new axes of growth throughout their life span. Secondary growth is initiated from groups of pluripotent cells, called meristems, which are established in the axils of leaves. Such meristems form lateral organs and develop into a side shoot or a flower, depending on the developmental status of the plant and environmental conditions. The phytohormone auxin is well known to play an important role in inhibiting the outgrowth of axillary buds, a phenomenon known as apical dominance. However, the role of auxin in the process of axillary meristem formation is largely unknown. In this study, we show in the model species Arabidopsis thaliana and tomato (Solanum lycopersicum) that auxin is depleted from leaf axils during vegetative development. Disruption of polar auxin transport compromises auxin depletion from the leaf axil and axillary meristem initiation. Ectopic auxin biosynthesis in leaf axils interferes with axillary meristem formation, whereas repression of auxin signaling in polar auxin transport mutants can largely rescue their branching defects. These results strongly suggest that depletion of auxin from leaf axils is a prerequisite for axillary meristem formation during vegetative development.     

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。     

Life history and population dynamics of the Japanese Yam,Dioscorea japonica Thunb.

The adaptive significance of the emergence mode ofDioscorea japonica was studied with respect to initial plant size (seed, bulbil and tuber) and light intensity, using mathematical simulation based on Yokoi's (1976) model. Under 1.5% full sunlight conditions, plants emerging with only one leaf did not develop a shoot system throughout the growing period (Hori and Oshima, 1986). Simulation indicated that, for this species of plant under poor productive conditions, the optimal time for switch-over from the vegetative to reproductive growth phase to maximize the tuber weight at the end of the growing period, occurred immediately following the start of autotrophic growth. By means of shoot growth patterns, small and large size plants acquired the ability of shade tolerance and shade avoidance, respectively. Further, the life history ofD. japonica could be expressed as a flow chart based on plant size and light intensity data.     

Quantitative variation in water-use efficiency across water regimes and its relationship with circadian, vegetative, reproductive, and leaf gas-exchange traits

Drought limits light harvesting, resulting in lower plant growth and reproduction. One trait important for plant drought response is water-use efficiency (WUE). We investigated (1) how the joint genetic architecture of WUE, reproductive characters, and vegetative traits changed across drought and well-watered conditions, (2) whether traits with distinct developmental bases (e.g. leaf gas exchange versus reproduction) differed in the environmental sensitivity of their genetic architecture, and (3) whether quantitative variation in circadian period was related to drought response in Brassica rapa. Overall, WUE increased in drought, primarily because stomatal conductance, and thus water loss, declined more than carbon fixation. Genotypes with the highest WUE in drought expressed the lowest WUE in well-watered conditions, and had the largest vegetative and floral organs in both treatments. Thus, large changes in WUE enabled some genotypes to approach vegetative and reproductive trait optima across environments. The genetic architecture differed for gas-exchange and vegetative traits across drought and well-watered conditions, but not for floral traits. Correlations between circadian and leaf gas-exchange traits were significant but did not vary across treatments, indicating that circadian period affects physiological function regardless of water availability. These results suggest that WUE is important for drought tolerance in Brassica rapa and that artificial selection for increased WUE in drought will not result in maladaptive expression of other traits that are correlated with WUE.     

Environmental heterogeneity and mechanism of stoichiometry properties of vegetative organs in dominant shrub communities across the Loess Plateau

 为了探究黄土高原灌丛群落中优势物种的根、茎和叶等营养器官之间碳(C)、氮(N)、磷(P)及其比值等化学计量特征的环境分异性及其与土壤养分的耦合性, 在甘肃省和宁夏回族自治区境内的3个灌丛集中分布区(甘肃南部、宁夏北部和甘肃西部)沿水热梯度选取41个样点进行样地调查。结果显示: 1)甘肃、宁夏灌丛群落的有机物质含量及P资源相对匮乏, 而N资源相对丰富。2)从甘肃南部、宁夏北部到甘肃西部, 生长季温度递增、年降水量递减, 与此耦合, 土壤养分也逐级递减, 沿着土壤养分梯度, 黄土高原优势灌丛根、茎和叶的C、N、P储量减少, 根和茎的C:N下降, 根、茎和叶的N:P上升, 但在宁夏北部和甘肃西部间差异不显著。同时, 3个优势灌丛分布区的优势灌丛各器官间营养元素的分配格局不同。3)土壤养分相对较高的区域优势灌丛间各器官营养元素储量无差异, 而土壤养分较低区域亲缘关系较远的优势灌丛间各器官的营养元素储量差异显著, 而亲缘关系较近的优势灌丛各器官营养元素储量差异不显著。黄土高原优势灌丛各器官C、N、P化学计量特征是植物体与土壤中化学元素耦合的结果, 当土壤养分逐渐升高时, 植物体内的化学元素储量也逐渐增多。该研究不仅有助于认识黄土高原优势灌丛化学计量环境分异规律, 而且有助于洞察不同土壤条件下C、N、P在优势灌丛营养器官间的分配格局和植物资源分配策略, 并为黄土高原植被的管理和恢复提供一定的理论基础。     

Distribution and levels of phytoecdysteroids in plants of the genus Silene during development

The purpose of the present work is the study of ecdysteroid distribution in annual and perennial Silene species during development. The experimental approach included the measurement of ecdysteroid levels in different plant organs and an evaluation of the contribution of individual organs to the total amount of 20-hydroxyecdysone (20E) produced by the plant. The highest concentrations of 20E were observed in reproductive organs. High levels were also found in leaves with lower levels in stems. Maximal ecdysteroid content for aerial parts was observed during periods of intense growth: at budding or flowering in annual species, and during vegetative growth or budding in perennial species. The contribution of the different organs to the overall ecdysteroid content changes during plant development. Leaves represent the main part of plant mass and 20E content. Reproductive organs represent a relatively small mass, but they contain high concentrations of ecdysteroids and, in terms of the amount of 20E they contain, their contribution is equal to that of stems. Arch.     

Plant reaction to drilling wastes of petroleum complex in the zone of Middle Taiga of Ob region

Data on the change in plant condition under the impact of drilling wastes (DWs) of petroleum clefts and on the transport of toxic elements from the stratum (soil) to vegetative organs are obtained. Stimulation of plant growth and productivity is revealed at a DW concentration in oligotrophic strata of up to 20% without translocations of their separate elements in vegetative organs.     

Multiple switches between vegetative and reproductive growth in annual plants

A model of growth and reproduction in annual plants was developed by Cohen (1971, J. Theor. Biol.33, 299–307) to determine the allocation strategy which maximizes seed yield. The model divides the plant into vegetative and reproductive parts and predicts that yield is maximized by a strategy consisting of a switch from purely vegetative to strictly reproductive growth. We generalize Cohen's model to include vegetative and reproductive loss terms. Both growth and loss rates are allowed to vary with time. Using optimal control theory we find that seed yield is maximized by a strategy consisting of multiple switches between vegetative and reproductive growth, for certain ranges of the model parameters. In natural systems a predictable vegetative loss burst may be necessary to promote multiple switches.     

植物同化物分配及其模型研究综述

目前生态系统模型模拟中所用的大多数同化物分配模型是经验性的。同化物分配对植物的生长、竞争及结构的形成有重要的影响,是植物生长的关键,也是植物生长模型中的薄弱环节。总结了影响同化物分配的因素：生理过程和环境因子。指出植物作为一个有机的整体,所有的生理过程都对其有影响,维管束作为各器官间的连接系统,以及同化物的运输管道,其性质对同化物分配有重要的影响。综述了环境因子特别是环境水分条件对同化物分配的影响。总结了以往研究中发现的、主要的同化物分配规律,指出同化物分配的模式极其复杂,分配过程完全是根据环境以及生长阶段变化而变化的、随机应变的过程。 对于同化物分配模型按照经验模型,目的性模型,源汇关系模型进行了总结归纳,分析指出：经验性模型应用最多但机理性差;功能平衡模型在模拟营养生长阶段同化物在条与根之间的分配很成功,但应用于其它器官之间很困难;最优化模型适于模拟平衡态下同化物的分配;源汇关系模型机理性最强,可模拟任何器官间的同化物分配,应用范围最广泛。 同化物研究取得了很大的进展,但研究中仍存在很多不足：对于各相关过程的研究存在不平衡性;整体水平上同化物分配的机理仍缺乏深入研究;同化物分配对于环境的响应方面的研究相对较弱;缺乏多环境因素的研究;缺乏长期的实验观测研究。作者认为环境与同化物分配相互关系的研究将成为日后研究中的热点问题。     

Optimal Reproductive Strategy of Plants, with Special Reference to the Modes of Reproductive Resource Allocation

Abstract A growth model for reproductive energy allocation pattern and schedule is proposed. Assumptions are as follows: (1) the assimilation rate for an individual is given by a logistic curve of vegetative dry weight; (2) size variability is expressed by the parameter W of the logistic curve (asymptotic value of vegetative dry weight); (3) a plant controls allocation of the assimilate to vegetative and reproductive structures so as to maximize the reproductive energy investment at the end of the growth period. The models were analyzed in comparison with field and experimental observations and gave reasonable explanations for the reproductive allocation pattern of individuals which reflects ecological preferences and life history characteristics, such as environmental conditions of habitats (stable or changing), length of life span (annual, biennial or perennial) and growth form (erectophile or planophile). Decreasing RA (reproductive allocation) with individual size and delayed switchover time from vegetative to reproductive growth were found in plants which occur in stable environments and have a more or less fixed growth period; in those which occur in changing environments where growth period depends on individual size, RAs that remain constant or increase with variations in individual size and early switchover time were detected. Most perennials conform to the former case, but annuals and biennials conform to the latter case. Under extremely overcrowded conditions, planophiles, which are much more subject to crowding effect than erectophiles, tend to have increasing RA with increasing size, while erectophiles tend to have almost constant RA irrespective of size. These trends are discussed in the light of the life history characteristics and ecological distribution of plant species studied.