Simulation of Potential Production and Optimum Population Quantitative Indices for the Second Hybrid Rice

The article established the HDRICE model by modifying the structure of the ORYZA1 model and revising its parameters by field experiments. The HDRICE model consists of the modules of morphological development of rice, daily dry matter accumulation and partitioning, daily CO2 assimilation of the canopy, leaf area, and tiller development. The model preferably simulated the dynamic rice development because of the thorough integration of the effects of temperature and light on the rates of rice development, photosynthesis, respiration, and. other ecophysiological processes. In addition, this model has attainable grain yield in the test experiment that showed the potential yield of cultivar Xieyou 46 ranged from 11 to 13 tons ha-~. Besides, the model was used to optimize the combinations of the transplanting date, seedling age and density for cultivar Xieyou 46 at Jinhua area, and the population quantitative indices to attain the potential yield such as maximum stems, effective panicles, filled grain number/leaf area, and so on. The result showed that the combination of transplanting date on July 25, seedling age of 35 days and base seedling density of 1.33 x 106ha-1 is the optimum combination for the second hybrid rice production in Jinhua County, China. And the maximum stems, the effective panicles, the filled grain per panicle, the peak of optimum LAI, LAI in later filling stage, and the filled grain number/leaf were 6.03×10^6ha, 3.99×10^6ha, 119.2, 8.59, 5-6, and 0.64, respectively.

Transgenic cry1Ab/vip3H+epsps Rice with Insect and Herbicide Resistance Acted No Adverse Impacts on the Population Growth of a Non-Target Herbivore, the White-Backed Planthopper, Under Laboratory and Field Conditions

Numerous Bt rice lines expressing Cry protein derived from Bacillus thuringiensis Berliner （Bt） have been developed since 1989. However, the potential risks posed by Bt rice on non-target organisms still remain debate. The white-backed planthopper （WBPH）, Sogatella furcifera （Horváth）, is one of the most economically important insect pests of rice in Asian countries and also one of the main non-target herbivores of transgenic rice. In the current study, impacts of transgenic cry1Ab/vip3H＋epsps rice （G6H1） with both insect and herbicide resistance on WBPH were evaluated to ascertain whether this transgenic rice line had potential risks for this sap-sucking pest under laboratory and ifeld conditions. The laboratory results showed that no signiifcant difference in egg developmental duration, nymphal survival rate and female fecundity was found for WBPH between G6H1 and its non-transgenic isoline （XS110）. However, the development duration of nymphs was signiifcantly shorter and female longevity signiifcantly longer when WBPH fed on G6H1 by comparison with those on its control. To verify the results found in laboratory, a 3-yr ifeld trial was conducted to monitor WBPH population using both the vacuum-suction machine and beat plate methods. Although the seasonal density of WBPH nymphs and total density of nymphs and adults were not signiifcantly affected by transgenic rice regardless of the sampling methods, the seasonal density of WBPH adults in transgenic rice plots was slightly lower than that in the control when using the vacuum-suction machine. Based on these results both from laboratory and ifeld, it is clear that our tested transgenic rice line will not lead higher population of WBPH. However, long-term ifeld experiments to monitor the population dynamics of WPBH at large scale need to be conducted to conifrm the present conclusions in future.

Modeling Dynamics of Leaf Color Based on RGB Value in Rice

This paper was to develop a model for simulating the leaf color changes in rice （Oryza sativa L.） based on RGB （red, green, and blue） values. Based on rice experiment data with different cultivars and nitrogen （N） rates, the time-course RGB values of each leaf on main stem were collected during the growth period in rice, and a model for simulating the dynamics of leaf color in rice was then developed using quantitative modeling technology. The results showed that the RGB values of leaf color gradually decreased from the initial values （light green） to the steady values （green） during the first stage, remained the steady values （green） during the second stage, then gradually increased to the final values （from green to yellow） during the third stage. The decreasing linear functions, constant functions and increasing linear functions were used to simulate the changes in RGB values of leaf color at the first, second and third stages with growing degree days （GDD）, respectively; two cultivar parameters, MatRGB （leaf color matrix） and AR （a vector composed of the ratio of the cumulative GDD of each stage during color change process of leaf n to that during leaf n drawn under adequate N status）, were introduced to quantify the genetic characters in RGB values of leaf color and in durations of different stages during leaf color change, respectively; FN （N impact factor） was used to quantify the effects of N levels on RGB values of leaf color and on durations of different stages during leaf color change; linear functions were applied to simulate the changes in leaf color along the leaf midvein direction during leaf development process. Validation of the models with the independent experiment dataset exhibited that the root mean square errors （RMSE） between the observed and simulated RGB values were among 8 to 13, the relative RMSE （RRMSE） were among 8 to 10%, the mean absolute differences （da） were among 3.85 to 6.90, and the ratio of da to the mean observation values （Clap） were among 3.04 to 4.90%. In addition, the leaf color model was used to render the leaf color change over growth progress using the technology of visualization, with a good performance on predicting dynamic changes in rice leaf color. These results would provide a technical support for further developing virtual plant during rice growth and development.

A Class of Second-Order Characteristic Difference Schemes for a Model of Population Dynamics

In this paper, a three level characteristic difference scheme is proposed for the model of age structured population with history dependent mortality and natality. It is proved that the scheme is second order convergent in the discrete l ∞ norm.

The Influence of Transgenic cry1Ab/cry1Ac,cry1C and cry2A Rice on Non-Target Planthoppers and Their Main Predators Under Field Conditions

Transgenic Bt rice has been shown to be an effective means of controlling Lepidoptera pests of rice. However, the potential roles of transgenic rice on planthoppers and their predators need to be investigated before its commercialization. Population density, species dominance and population dynamics are important parameters of arthropods populations in field. So the impacts of three transgenic Bt rice strains expressing crylAb/crylAc, crylC and cry2A on population density, species dominance and population dynamics of three species of planthoppers （Nilaparvata lugens, Sogatella furcifera and Laodelphax striatellus） and their three main predators （ Cyrtorhinus lividipennis, Pirata subpiraticus and Theridium octomaculatum） were evaluated at three sites in Hubei Province, China, in the current study. The results showed that among three species of planthoppers, both in transgenic and non-transgenic rice field, the predominant species ofplanthoppers within phytophagous guild was S. furcifera at any site either growing season （46-50%）. Significantly higher population density ofN. lugens was observed in T2A-1 field relative to Minghui 63 field at Wuxue in 2010. The species dominance of predator, P. subpiraticus, in TT51 field was significantly higher than that in T 1 C-19 and T2A-1 fields in 2009 at Xiaogan site. Sampling date significantly influenced six arthropods except for P. subpiraticus in 2010. The interaction between rice strain^sampling date had no significant adverse effects on the population dynamics of three species of planthoppers and their predators, except for several individual species in 2009. The interaction among rice strain^sampling date^sampling site also had no significant effect on six arthropods except for S. furcifera in 2009. The results indicated that transgenic Bt rice expressing crylAb/crylAc, cry2A and crylC had no significant adverse effects on the population dynamics of three planthoppers and their predators in most investigated data and sampling site.

Analyses of the Temporal Development and Yield Losses due to Sheath Blight of Rice (Rhizoctonia solani AG1.1a)

Sheath blight of rice, caused by Rhizoctonia solani AG 1. 1a, has become the most important disease and caused serious yield losses in some major rice-growing regions in China in recent years. In the present study, field plot experiment was conducted to examine the relationships between disease intensity and inoculum density （ID）, the seasonal disease epidemic dynamics, and yield reductions due to disease damages. Results from the experiment demonstrated that the areas under progress curves of disease severity and those of percent rice tillers diseased were positively and closely related to the relative initial ID of the pathogen. The inoculum density-disease （IDD） relationships were simulated and the impractical linear models were obtained. Both logistic and Gompertz functions could be used to simulate the disease progress dynamics in time, but the progress curves of the disease severity were modeled better by the Gompertz than by logistic function. However, the Richards function was found to be the best in simulating the disease progress curves when a most appropriate value was chosen for the shape parameter m by using the computer software Epitimulator. Sheath blight infection decreased rice yield very significantly and a yield reduction of 40% was recorded in rice crop with the highest inoculum density. Rice yield was linearly and negatively correlated with the disease severity and the percent tillers affected. The simulated models for all these relationships were computed through executing Epitimulator software and were presented in this paper.

Occurrence Regularity of Major Damage Generations of Nilaparvata lugens(Stl) in Single Cropping Medium Rice Region in Sandu County of Guizhou Province

In order to clarify occurrence regularity of major damage generations of Nilaparvata lugens( Stl) in Sandu Shui Autonomous County( Sandu County for short),Guizhou Province,a karst single cropping medium rice region,the population dynamics of N. lugens were systematically studied using the methods of light trap and systematic field survey from 2009 to 2011. The results showed that the number of immigration generations caught by light trap and the actual population of N. lugens in fields were different among three years. The daily maximum trapping numbers of N. lugens amounted to 6 688 in 2009,which were 15. 3 and 2. 5 times of that in 2010 and 2011,respectively. The peak numbers in prediction nursery were 10 777,4 630 and 1 615 heads per hundred hills in 2009,2010 and 2011,respectively. The forth and fifth generations of N. lugens were the major damage generations in single cropping medium rice fields,and the initial immigration day was significantly related with primary-peak day. The occurrence degree of adults and nymphs of N. lugens varied with years and transplanting periods,and the peak days of N. lugens nymphs were from late July to early August in 2010 and 2011. The occurrence peaks of adults and nymphs in late transplanting paddy field were later than that in the early one. Meanwhile,the coexisted various growth periods of rice,due to time differences of transplanting,were conducive to inhabitation and reproduction of N. lugens. The population dynamics of spiders and Cyrtohinus lividipennis well synchronied with that of N. lugens,but predatory capacity of spiders and C. lividipennis was not enough to control N. lugens.

An Algorithm for the Stochastic Simulation of Gene Expression and Heterogeneous Population Dynamics

We present an algorithm for the stochastic simulation of gene expression and heterogeneous population dynamics.The algorithm combines an exact method to simulate molecular-level fluctuations in single cells and a constant-number Monte Carlo method to simulate time-dependent statistical characteristics of growing cell populations.To benchmark performance,we compare simulation results with steadystate and time-dependent analytical solutions for several scenarios,including steadystate and time-dependent gene expression,and the effects on population heterogeneity of cell growth,division,and DNA replication.This comparison demonstrates that the algorithm provides an efficient and accurate approach to simulate how complex biological features influence gene expression.We also use the algorithm to model gene expression dynamics within"bet-hedging"cell populations during their adaption to environmental stress.These simulations indicate that the algorithm provides a framework suitable for simulating and analyzing realistic models of heterogeneous population dynamics combining molecular-level stochastic reaction kinetics,relevant physiological details and phenotypic variability.

An individual-based probabilistic model for simulating fisheries population dynamics

The purpose of stock assessment is to support managers to provide intelligent decisions regarding removal from fish populations.Errors in assessment models may have devastating impacts on the population fitness and negative impacts on the economy of the resource users.Thus,accuracte estimations of population size,growth rates are critical for success.Evaluating and testing the behavior and performance of stock assessment models and assessing the consequences of model mis-specification and the impact of management strategies requires an operating model that accurately describe the dynamics of the target species,and can resolve spatial and seasonal changes.In addition,the most thorough evaluations of assessment models use an operating model that takes a different form than the assessment model.This paper presents an individual-based probabilistic model used to simulate the complex dynamics of populations and their associated fisheries.Various components of population dynamics are expressed as random Bernoulli trials in the model and detailed life and fishery histories of each individual are tracked over their life span.The simulation model is designed to be flexible so it can be used for different species and fisheries.It can simulate mixing among multiple stocks and link stock-recruit relationships to environmental factors.Furthermore,the model allows for flexibility in sub-models(e.g.,growth and recruitment)and model assumptions(e.g.,age-or size-dependent selectivity).This model enables the user to conduct various simulation studies,including testing the performance of assessment models under different assumptions,assessing the impacts of model mis-specification and evaluating management strategies.

An Accelerated Method for Simulating Population Dynamics

We present an accelerated method for stochastically simulating the dynamics of heterogeneous cell populations.The algorithm combines a Monte Carlo approach for simulating the biochemical kinetics in single cells with a constant-number Monte Carlo method for simulating the reproductive fitness and the statistical characteristics of growing cell populations.To benchmark accuracy and performance,we compare simulation results with those generated from a previously validated population dynamics algorithm.The comparison demonstrates that the accelerated method accurately simulates population dynamics with significant reductions in runtime under commonly invoked steady-state and symmetric cell division assumptions.Considering the increasing complexity of cell population models,the method is an important addition to the arsenal of existing algorithms for simulating cellular and population dynamics that enables efficient,coarse-grained exploration of parameter space.

配施硅肥对稻飞虱取食量、田间种群数量及水稻产量的影响

为探明增施硅肥在水稻田稻飞虱绿色防控中的作用,本文采用室内蜜露测定、田间盆拍调查等方法研究了在广西代表性土壤条件下增施硅肥对稻飞虱蜜露量、田间种群数量及水稻产量的影响。结果表明:褐飞虱Nilaparvata lugens St l和白背飞虱Sogatella furcifera Horváth在施硅量为15 kg/hm^(2)和45 kg/hm^(2)水稻上的平均蜜露量均显著低于不施硅对照。在水稻分蘖期,与不施硅对照相比,15 kg/hm^(2)施硅处理下两个试验点稻飞虱发生量均显著减少;45 kg/hm^(2)施硅处理下宾阳试验点的稻飞虱发生量显著减少,而合浦试验点在水稻分蘖盛期稻飞虱发生量虽未显著减少,但水稻分蘖后期稻飞虱发生量极显著低于不施硅对照,减少了51.03%。在水稻灌浆期,与不施硅对照相比,宾阳试验点15 kg/hm^(2)和45 kg/hm^(2)施硅处理稻飞虱的发生量均极显著减少,而合浦试验点稻飞虱发生量没有显著变化。15 kg/hm^(2)和45 kg/hm^(2)施硅处理的稻谷千粒重均显著高于不施硅对照,产量比不施硅对照提高1.88%~9.05%。增施硅肥可明显降低水稻田稻飞虱的取食量和田间种群发生量,同时在一定程度上提高了稻谷产量,因此,水稻增施硅肥有助于广西稻飞虱的绿色防控。

盘锦地区3个主栽品种灰飞虱田间种群动态

为探明盘锦地区近年水稻主栽品种上灰飞虱种群动态特征,连续2 a对盘锦3个水稻品种上灰飞虱发生情况进行调查,结果表明,2022年各品种灰飞虱发生总量显著高于2023年,各品种间灰飞虱总量没有显著差异;不同品种上灰飞虱田间种群动态趋势大体一致,但2023年9月灰飞虱种群数量低于2022年同时期。

Field evaluation of effects of transgenic cry1Ab/cry1Ac,cry1C and cry2A rice on Cnaphalocrocis medinalis and its arthropod predators

The impacts of transgenic Bt rice on target pests and their predators need to be clarified prior to the commercialization of Bt rice.In this study,the percentages of folded leaves of three transgenic Bt rice lines and non-transgenic parental rice line caused by Cnaphalocrocis medinalis were studied over two successive growing seasons.In addition,the population densities,relative abundance and population dynamics of C.medinalis and four species of its natural arthropod predators were investigated at three sites in China.The results showed that rice line significantly affected the percentages of folded leaves and population densities of C.medinalis larvae.Significantly higher percentages of folded leaves were observed on the non-transgenic rice compared with the three transgenic Bt rice on most sampling dates.Significantly higher densities of C.medinalis larvae and higher relative abundance of C.medinalis within phytophages were found on non-transgenic rice compared with three transgenic Bt rice at different sites across the study period.The population dynamics of C.medinalis larvae were significantly affected by rice line,rice line×sampling date,rice line×year,rice line×sampling date×year.However,there was little,if any,significant difference in the relative abundance,population density and population dynamics of the four arthropod predators between the three Bt rice lines and non-transgenic rice.The results of this study indicate that the Bt toxin in transgenic Bt rice can effectively suppress the occurrence of C.medinalis,but has no significant effects on the occurrence of the four predatory arthropod species.

拟禾本科根结线虫种群密度与旱稻产量损失的关系

本研究旨在探讨土壤中拟禾本科根结线虫(Meloidogyne graminicola)的初始种群密度对旱稻产量损失的影响。通过室外网室盆栽试验,在旱种旱管模式下测定了土壤不同初始种群密度对旱稻产量和线虫繁殖的影响。研究结果表明,在2~200个卵和二龄幼虫/100 cm^(3)土的初始种群密度下,旱稻根长、根重、株高、分蘖数、穗长、千粒重和单盆谷粒重与土壤线虫初始种群密度呈极显著负相关,符合一元回归方程;旱稻产量随着土壤初始种群密度的增加,其损失率增加,在初始密度为2个卵和二龄幼虫/100 cm^(3)土时,旱稻产量损失率为28.4%,接种密度为200个卵和二龄幼虫/100 cm^(3)土时,损失率最大,为67.8%;随着线虫初始种群密度的增加,线虫的繁殖系数呈现降低的趋势。利用Seinhorst模型,初始线虫种群密度与相对产量的关系式为Y=0.24+0.76(0.3252)(Pi)。在旱种旱管模式下,拟禾本科根结线虫在2~200个卵和二龄幼虫/100 cm^(3)土的初始种群密度下与旱稻产量损失呈极显著正相关,表明拟禾本科根结线虫对旱稻的危害风险性较高。

水稻田埂捕食性天敌多样性与种群动态

农田生态系统中天敌群落具有重要的生态控害功能。受作物种植技术与栽培管理措施影响,稻田自然生草的田埂成为天敌的理想避护所。本研究连续2年在中稻整个生长期,应用陷阱法(Pitfall trap)对水稻田埂的捕食性天敌群落与动态进行了系统监测,明确了水稻田埂捕食性天敌的种群和多样性格局,并分析了步甲、蜘蛛和泽蛙在中稻不同时期的变化。结果表明:两年共捕获步甲类13属23种1100头,蜘蛛类9科1928头,泽蛙Rana limnocharis 1485头。步甲、蜘蛛和泽蛙在年度间中稻的不同生长发育阶段,种群数量动态表现出差异化波动。水稻不同生育期Pitfall陷阱捕获步甲的个体数、多样性指数、均匀度指数和优势度指数在年际间变化显著;蜘蛛则表现在水稻不同生育期其被捕获种群数量有显著差异;2019年水稻分蘖期泽蛙个体数显著高于抽穗成熟期,而2020年拔节孕穗期泽蛙个体数显著高于分蘖期。综上表明,水稻田埂系统具有支持捕食性天敌多样性及其潜在生态控害作用的功能。因此,建议在高标准农田整治过程中,适当保留一定数量的生草田埂与沟渠,以实现天敌保育。

辽河三角洲稻田不同管理方式稻飞虱种群动态

为探明辽河三角洲稻田不同管理方式下稻飞虱发生情况,连续2 a进行了稻飞虱发生总量及种群动态趋势调查,结果表明,常规稻田粗放管理方式下,稻飞虱发生总量最高(65.67头/穴),其次为蟹田清洁生产系统,而常规稻田清洁生产方式下,稻飞虱发生总量最低(46.80头/穴);三类稻田稻飞虱种群动态趋势大体一致,2022年与2023年没有显著差异。

人口规模与教育资源配置良性互动机制的动态仿真

我国人口规模与教育资源配置形成了恶性循环。以社会宏观动力学为分析框架,基于2000—2019年面板数据,采用Vensim PLE软件,构建人口规模与教育资源配置互动机制系统动力学模型。研究表明:2024年开始,人口规模下降速度将逐年加快,教育市场将出现结构性萎缩,教育资源投入总量和速度将提高;人口规模对生产水平敏感;教育资源市场配置对人口增速、权力巩固程度、权力中心化程度、物力教育资源敏感。基于研究结论,提出两者良性互动的调适策略:保持经济高质量发展,降低生育养育成本;将生育权还给家庭,全面放开生育;巩固“双减”政策成效,引导教育需求;降低权力中心化程度,利用教育市场优势;加大教育资源投入,促进优质教育资源均衡。

Hydrate agglomeration modeling and pipeline hydrate slurry flow behavior simulation

Dynamic modeling and numerical simulation of hydrate slurry flow behavior are of great importance to offshore hydrate management.For this purpose, a dynamic model of hydrate agglomeration was proposed in this paper.Based on population balance equation, the frame of the dynamic model was established first, which took both hydrate agglomeration and hydrate breakage into consideration.Then, the calculating methods of four key parameters involved in the dynamic model were given according to hydrate agglomeration dynamics.The four key parameters are collision frequency, agglomeration efficiency, breakage frequency and the size distribution of sub particles resulting from particle breakage.After the whole dynamic model was built, it was combined with several traditional solid–liquid flow models and then together solved by the CFD software FLUENT 14.5.Finally, using this method, the influences of flow rate and hydrate volume fraction on hydrate particle size distribution, hydrate volume concentration distribution and pipeline pressure drop were simulated and analyzed.

CO_(2)浓度升高下水稻株高、茎蘖与SPAD动态响应及其模拟

水稻是中国主要粮食作物,CO_(2)浓度升高直接影响水稻的生产。但在CO_(2)浓度升高条件下,水稻生长发育的动态特征及其模型模拟研究尚不足。为探究水稻株高、分蘖与SPAD(表征叶绿素相对含量)动态对CO_(2)浓度升高的响应特征,在2017年与2018年,以常规粳稻“南粳9108”为试验材料,利用开顶式气室(OTC),设置背景大气CO_(2)浓度与CO_(2)浓度升高(+200μmol·mol^(-1))两个处理,并采用Logistic方程、Logistic修正方程和多项式回归方程分别对三者的动态曲线进行定量描述。结果表明:CO_(2)浓度升高对抽穗前的株高无影响,但当抽穗1周后的有效积温(GDD)大于720℃·d时,显著增加了最终株高,其增幅为7.1%(P<0.05)。因此,水稻生长的环境温度调控株高对CO_(2)浓度升高的响应。株高可用大于10℃的GDD和CO_(2)响应比建立的Logistic方程进行有效模拟(r~2>0.953)。CO_(2)浓度升高总体上提高了水稻的分蘖能力,并且以移栽后天数和CO_(2)响应比为驱动变量,采用Logistic修正方程有效地模拟了茎蘖增长与消亡动态(r~2>0.971)。CO_(2)浓度升高仅增加了2017年抽穗后35 d旗叶与倒二叶的SPAD(P<0.05),但对其他时期或叶位SPAD无显著影响。因此,水稻SPAD对CO_(2)升高的响应因叶位选择与测定时间而异。多项式回归模型能有效模拟抽穗后不同叶位SPAD动态(r~2>0.960),其中抽穗后天数和CO_(2)响应比是驱动变量。综上所述,CO_(2)浓度升高对水稻株高、茎蘖与SPAD具有促进作用,其效应与外界因素有关。模型能较好地模拟水稻株高、茎蘖与SPAD对CO_(2)浓度升高的动态响应。该研究可为未来CO_(2)浓度升高条件下,水稻生长发育和产量形成的预测提供科学依据。

稻田养鸭对稻飞虱的控制作用

为了探明稻田养鸭对水稻病虫害的控制作用,于2003年4至11月在湖南省桃江县建立稻田养鸭试验示范区.研究结果表明,在中稻田,放鸭区第四代、第五代稻飞虱百蔸虫量较空白区虫量下降70.2%和72.4%;晚稻田养鸭区第四代、第五代稻飞虱虫量较空白区下降56.2%和64.7%,表明稻鸭共栖对稻飞虱起到了稳定、持久的控制作用.放鸭区不需用药防治稻飞虱,经济效益明显.