Effect of elevated carbon dioxide and water stress on gas exchange and water use efficiency in corn

CO₂ has been predicted to increase in the future, and thus leading to possible changes in precipitation patterns. The objectives of this study were to investigate water use and canopy level photosynthesis of corn plants, and to quantify water use efficiency in corn plants under two different CO₂ levels combined with four different water stress levels. Corn plants were planted in sunlit plant growth chambers and a day/night temperature of (28/18 °C) was applied. From 21 days after emergence (DAE), the eight treatments including two levels of carbon dioxide concentrations (400 and 800 μmol mol⁻¹) and four levels of water stress (well-watered control, “mild”, “moderate”, and “severe” water stress) treatments at each CO₂ level were imposed. Height, number of leaves, leaf lengths, and growth stages of corn plants were monitored from nine plants twice a week. Corn plants were separately collected, dried, and analyzed for the biomass accumulation at 21 and 60 DAE. Soil water contents were monitored by a time domain reflectometry (TDR) system (15 probes per chamber). The “breaking points” (changes from high to low rates of soil water uptake) were observed in the bottom of soil depth for the water stressed conditions, and the “breaking points” under ambient CO₂ appeared 6-9 days earlier than under elevated CO₂. Although approximately 20-49% less water was applied for the elevated CO₂ treatments than for ambient CO₂ from 21 DAE, higher soil water contents were recorded under elevated CO₂ than under ambient CO₂. However, corn growth variables such as height, leaf area, and biomass accumulation were not significantly different in CO₂ or water stressed treatments. This result may be explained by considering that significant differences in canopy level gross photosynthesis among the water stress treatments was observed only toward the end of the experiment. The higher soil water contents observed under elevated CO₂ resulted mainly from less water use than under ambient CO_2. WUE (above ground biomass per water use since 21 DAE) at the final harvest was consistently higher and varied with a smaller range under elevated CO₂ than under ambient CO₂. This study suggests that less water will be required for corn under high-CO₂ environment in the future than at present.     

The Static Fertilization Experiment at the Start and the End of the 20th Century

Changes of yields, nitrogen uptake on the zero plots and nitrogen balances are discussed in the course of the decades at the Static Fertilization Experiment exemplary. 1991-2000 yields of cereals on the fertilized plots were nearly 200% in comparison to 1906-1915. At potatoes and sugar beets increase of yields was smaller. In the middle of all crops 52kg/ha nitrogen were taken up on the unfertilized plots in the years 1959-2000. Since there is a balance in the soil this nitrogen can only derived from the air. On the PK plots the atmogenic nitrogen input is 6kg/ha still higher. Crops with a long vegetation period like winter wheat and sugar beets take up more atmogenic nitrogen than such with a shorter vegetation period like summer barley and potatoes. The atmogenic nitrogen input per day of vegetation period is between 0,24 (winter wheat) and 0,38 (sugar beet)kg/ha and day. Nitrogen balances of the more important variants show that nitrogen uptake is higher than nitrogen input for a long time. In comparison of the decades 1961-1970 and 1991-2000 the best effect is in the case of mineral fertilization alone, also at increasing nitrogen input at the end of the century. The reason is the optimal control of nitrogen amount and time of application. In contrast organic fertilization and nitrogen release from the organic matter you can't control with the result of more unfavourable balances.     

黑河地区大豆脂肪和蛋白质的积累与开花到成熟期间气象因子的关系

本文将大豆开花至成熟期间分为九个生育时段,建立脂肪、蛋白质与气象因子的积分回归方程,并对每个生育时段中温度、降水、日照的时间分布所导致籽实脂肪、蛋白质含量发生变化的相关规律进行了初步研究。结果认为,每一单位温度(℃)、降水(mm)、日照(小时)在大豆脂肪、蛋白质累积的不同生育时段中所起的作用是不同的(正效应或负效应),同样的作用在量上也有较大的差别。这是一个品种在当地多年种植所产籽粒中脂肪、蛋白质含量存在差异的主要原因。其中降水量具有决定性作用。大豆脂肪与蛋白质的形成对7月下旬至8月上旬气象因子的不同要求,是达成两者含量呈负相关的主要原因。根据不同生育阶段气象因子对脂肪、蛋白质累积的不同效应情况,将脂肪、蛋白质累积的全过程分为四个时期。     

稻米蛋白质及其组分研究概况及其对稻米品质的影响

稻米蛋白质是决定其食味品质的重要因素,稻米蛋白质含量通常与米饭的食味品质呈显著负相关。作为典型的数量性状,稻米蛋白质含量受环境因素的影响较大。然而,稻米蛋白质含量及其构成的决定机制及环境因素对其的影响等方面还有诸多不明之处,其影响食味品质的机理也不清晰。本文综述了稻米蛋白质的种类、结构及其分布,稻米蛋白质的合成与积累过程以及蛋白质含量的遗传控制和影响因素,概括了稻米蛋白质及其组分含量与稻米品质关系的研究进展,为优质水稻的品种筛选及调优栽培提供参考和借鉴。     

杂交粳稻食味品质的遗传及相关分析

以9个新育成的BT型粳稻不育系和5个恢复系为亲本,采用p×q不完全双列杂交（NCⅡ）设计配制45个杂交组合,对其F1代食味品质性状进行遗传及相关分析。结果表明：食味品质性状同时受加性效应和非加性效应的影响;食味值与直链淀粉含量和蛋白质含量呈极显著负相关;在产量性状方面,食味值与实粒数、结实率极显著相关,各产量性状对食味品质性状均存在较大的影响;关于叶型对食味品质的影响主要是倒1叶的长宽、倒3叶的宽度以及倒1叶、倒2叶的基角开角,而叶片厚度、倒2叶长宽、倒3叶的基角开角的影响微弱。     

基于MODIS/EVI时间序列数据分析冰冻灾害对植被绿叶始期的影响(英文)

In the field of global changes, the relationship between plant phenology and climate, which reflects the response of terrestrial ecosystem to global climate change, has become a key subject that is highly concerned. Using the moderate-resolution imaging spectroradiometer (MODIS)/enhanced vegetation index(EVI) collected every eight days during January- July from 2005 to 2008 and the corresponding remote sensing data as experimental materials, we constructed cloud-free images via the Harmonic analysis of time series (HANTS). The cloud-free images were then treated by dynamic threshold method for obtaining the vegetation phenology in green up period and its distribution pattern. And the distribution pattern between freezing disaster year and normal year were comparatively analyzed for revealing the effect of freezing disaster on vegetation phenology in experimental plot. The result showed that the treated EVI data performed well in monitoring the effect of freezing disaster on vegetation phenology, accurately reflecting the regions suffered from freezing disaster. This result suggests that processing of remote sensing data using HANTS method could well monitor the ecological characteristics of vegetation.     

VaR数学模型及其计算方法

VaR(Value at Risk)是一种以规范的统计技术来度量市场风险的新标准,目前在金融数学领域被广泛使用,它是在正常的市场条件下,给定一定时间区间和置信水平,测度最大损失的数学方法。传统的VaR计算方法在计算开放式基金时,可能存在着高估风险的情况,对数正态分布假设下得到的风险值(VaR)要比正态分布假设下的风险值更接近实际值。本文着重论述了VaR模型的数学原理以及该模型的计算方法,运用对数正态分布假设来评估开放式基金的风险,以验证其结果是否更加接近实际风险值。     

Gradient analysis of an eastern sand savanna's woody vegetation,and its long-term responses to restored fire processes

Little information is available comparing historic and modern sand savannas, and how remnants respond to restored fire. We compared short- and long-term effects of restored fire on the Tefft Savanna, a 197 ha eastern sand savanna in northwest Indiana that had undergone three decades of fire protection. U.S. Public Land Survey data from Tefft in 1833 indicate black and white oak barrens, and pin oak savanna, with trees averaging 50 stems/ha and 4 m²/ha basal area. We used ordination and a digital elevation model to assess topographic distribution of tree species in 1986. In 1986, we also compared initial effects of high- and low-intensity dormant season fire on woody vegetation among nine blocks containing black oak, white oak, and pin oak stands. Twenty years later, we compared the same blocks, all of which had been burned three times per decade with low-intensity fires. In 1986, black oak, white oak and pin oak occurred across a gradient of decreasing elevation and slope. At that time, unburned black oak and white oak stands averaged >400 stems/ha and about 10 m²/ha basal area, and their smaller size classes contained non-oak woody vegetation that apparently had invaded with fire exclusion. After initial burns, black oak and white oak stands receiving high-intensity fire averaged <200 stems/ha and had significantly lower oak canopy cover and basal area than unburned stands. Stands receiving low-intensity fire had intermediate oak canopy cover, with basal area similar to unburned stands. Pin oak stands were more fire-resistant, apparently because spring flooding often reduced fire effects. Density, cover and basal area of non-oak tree species were much lower than oaks, and were not reduced by initial burning. Repeated low-intensity burning over 20 years tended to maintain structure caused by initial fires. However, it reduced lower size class stem densities, promoted post-fire sprouting into the shrub layer, and allowed oak basal area to increase in larger size classes. Time since fire regulated shrub layer structure on a 4-year cycle. Density and cover of trees and shrubs returned to pre-burn conditions by the second and fourth growing seasons after fire, respectively, with non-oak tree species exceeding pre-burn cover and density by the fourth season. These results suggest that high-intensity fire is more important than repeated low-intensity burning in structuring and restoring eastern sand savanna, and that non-oak tree species, once established, may be resistant to low-intensity fire.     

基于MODIS／EVI时间序列数据分析冰冻灾害对植被绿叶始期的影响

1数据和方法1．1研究区域介绍长江流域位于北纬24°27’-35°54’,东经90°13’-122°19’,南北跨11个纬度,东西距32个经度,呈东西长、南北短的流域平面形状。流域面积1800000hmz,约占全国国土面积的18．75％。由于其位置的特殊性及地形因素,长江流域是受拉尼娜现象影响最严重的地区。