直剪法用于糙米内摩擦角的测定与研究

利用土工合成材料综合测定仪（直剪仪）,以水分含量14.57%的糙米为样品,测定了在不同的法向压应力、不同的剪切速率下糙米的剪切应力并计算出内摩擦角。实验结果表明：糙米的剪切应力随着法向压应力（25kPa～100kPa）的增大而增大;剪切速率（1.33mm/min～2.67mm/min）较低时糙米的内摩擦角随着法向压应力的增大而减小;随着剪切速率（1.33mm/min～5.20mm/min）的增大,糙米的内摩擦角减小。     

银杏-杜仲叶发酵物对脂多糖应激肉仔鸡的肠道功能和免疫反应的影响

本试验旨在研究饲粮中添加银杏-杜仲叶发酵物（FGEL）对脂多糖（LPS）应激肉仔鸡的生长性能、肠道结构、消化吸收功能和免疫反应的影响，并与未发酵银杏-杜仲叶（GEL）进行比较。采用2×3双因子试验设计，即2种免疫应激处理（腹腔注射LPS或注射等量生理盐水）和3种饲粮处理（基础饲粮及在基础饲粮中添加0.40%GEL或0.40%FGEL的试验饲粮）。选取1日龄健康爱拔益加（AA）肉仔鸡360只，随机分为6个处理，每个处理均设6个重复，每个重复10只鸡。试验期为21 d。在试验第13、15、17、19和21天，3个应激处理的试鸡腹腔注射500μg/kg BW的LPS，其他3个处理注射等量的生理盐水。在试验第21天最后1次注射后2～4 h进行屠宰取样。结果表明：1）与对照饲粮相比，饲粮添加FGEL的肉仔鸡料重比（F/G）有显著改善（P=0.024），饲粮添加FGEL显著缓解了LPS应激肉仔鸡平均日增重（ADG）(P=0.023)和血清D-木糖的含量（P=0.011）的降低。2）与对照饲粮相比，饲粮添加FGEL显著缓解了LPS应激肉仔鸡十二指肠（P=0.011）和空肠（P=0.030）的相对重量...     

Modelling Wheat Stomatal Resistance in Hourly Time Steps from Micrometeorological Variables and Soil Water Status

An accurate estimation of stomatal resistance (r_S) also under drought stress conditions is of pivotal importance for any process‐based prediction of transpiration and the energy budget of real crop canopies and quantification of drought stress. A new model for r_S was developed and parameterized for winter wheat using data from field experiments accounting for the influences of net radiation (R_Net), air temperature (T_Air) and vapour pressure deficit of the atmosphere (VPD) interacting with an average water potential in the rooted soil (ψ_RootedSoil). r_S is simulated with a limiting factor approach as maximum of the metabolic (related to photosynthesis) and hydraulic (related to drought stress) acting influences assuming that, if drought stress occurs, it will dominate stomatal control: r_S = max(r_S(T_Air), r_S(R_Net), r_S(VPD, ψ_RootedSoil)). This transitional approach is suited to reproduce measured daily time courses of r_S with a varying accuracy for the single measurement dates but performed satisfactorily for the whole data set (r² = 0.63, RMSE = 59 s m^?1, EF = 0.60). This new semi‐empiric approach calculates r_S directly from external environmental conditions. Therefore, it can be easily implemented in existing model frameworks as link between operational crop growth models that use the concept of radiation use efficiency instead of mechanistic photosynthesis modelling and soil–vegetation–atmosphere transport models.     

How do timing,duration, and intensity of drought stress affect the agronomic performance of winter rye?

Winter rye (Secale cereale L.) will be especially affected by drought induced yield losses in Central and Eastern Europe in the future because it is predominantly cultivated on low-fertile soils with a poor water-holding capacity. In order to examine the performance of winter rye under different drought conditions, field experiments were carried out during the years 2011, 2012, and 2013 near Braunschweig, Germany. Two sets of genotypes were tested under severe, mild, pre-anthesis, and post-anthesis drought stress in rain-out shelters as well as under rainfed and well-watered conditions. The grain, straw, and total above ground biomass yields, harvest index, grain yield components, leaf area index (LAI), and phenological characteristics were examined, as well as phenotypic correlations between grain yield and further characteristics. Drought induced grain yield reduction ranged from 14 to 57%, while straw yield and harvest index were lesser affected by drought than the grain yield. Under drought conditions, fully ripe was reached up to twelve days earlier than under non water-limited conditions. Pre-anthesis drought mainly reduced spikes m⁻² and kernels spike⁻¹ while drought during grain filling reduced the 1000-kernel weight (TKW) only. The grain yield was positively associated with straw yield, spikes m⁻², and kernels spike⁻¹ under water limited conditions while the TWK was only positively associated with grain yield under drought during grain filling. Consequently, high pre-anthesis biomass as well as high numbers of spikes m⁻² and kernels spike⁻¹ are especially important for obtaining high grain yields under water-limited conditions. Focusing on these traits is, therefore, recommendable for developing drought tolerant rye genotypes.     

Drought Tolerance and Water Use of Cereal Crops: A Focus on Sorghum as a Food Security Crop in Sub‐Saharan Africa

Sub‐Saharan Africa (SSA) faces twin challenges of water stress and food insecurity – challenges that are already pressing and are projected to grow. Sub‐Saharan Africa comprises 43 % arid and semi‐arid area, which is projected to increase due to climate change. Small‐scale, rainfed agriculture is the main livelihood source in arid and semi‐arid areas of SSA. Because rainfed agriculture constitutes more than 95 % of agricultural land use, water scarcity is a major limitation to production. Crop production, specifically staple cereal crop production, will have to adapt to water scarcity and improved water productivity (output per water input) to meet food requirements. We propose inclusion and promotion of drought‐tolerant cereal crops in arid and semi‐arid agro‐ecological zones of SSA where water scarcity is a major limitation to cereal production. Sorghum uniquely fits production in such regions, due to high and stable water‐use efficiency, drought and heat tolerance, high germplasm variability, comparative nutritional value and existing food value chain in SSA. However, sorghum is socio‐economically and geographically underutilized in parts of SSA. Sorghum inclusion and/or promotion in arid and semi‐arid areas of SSA, especially among subsistence farmers, will improve water productivity and food security.     

动态细分饲粮营养供给对肉鸡生产性能、肉品质、氮与磷代谢率及血清生化指标的影响

本试验旨在根据肉鸡生长曲线及动态营养需要,研究动态细分饲粮营养供给对肉鸡生产性能、肉品质、氮、磷代谢率及血清生化指标的影响。选取1日龄爱拔益加(AA)肉鸡240只(公母各占1/2),随机分为3个组,分别为A组:每3.5 d 1个营养标准(1~7日龄1个营养标准);B组:每7 d 1个营养标准;C组:每14 d 1个营养标准。每组8个重复,每个重复10只鸡,试验期42 d。结果表明:1)C组肉鸡的平均日增重(ADG)显著高于A、B组(P0.05),料重比(F/G)显著低于A组(P0.05)。A、B组肉鸡生产性能指标差异均不显著(P0.05)。不同动态细分饲粮营养供给方式对肉鸡肉品质的影响无显著差异(P0.05)。2)不同动态细分饲粮营养供给方式对肉鸡氮、磷代谢率的影响无显著差异(P0.05)。3)肉鸡28日龄时,C组肉鸡血清尿素氮(UREA)含量显著高于A组(P0.05);42日龄时,C组肉鸡血清UREA含量显著高于A、B组(P0.05),但A、B组肉鸡血清UREA含量差异不显著(P0.05)。4)不同动态细分饲粮营养供给方式对肉鸡血清皮质酮(CORT)含量及总抗氧化能力(T-AOC)的影响差异不显著(P0.05)。综上所述,每14 d 1个营养标准可使肉鸡的生产性能达到最佳,从实际操作的复杂性考虑,每7 d 1个营养标准可更好地满足饲粮的氨基酸平衡。     

复盐胁迫下结缕草K~+、Na~+吸收与运输的特点

用2种中性盐(Na Cl和Na2SO4)模拟江苏沿海滩涂土壤盐碱条件,配制不同复盐浓度,对大穗结缕草(Zoysia macrostachya)和中华结缕草(Zoysia sinica)进行30 d复盐胁迫处理,分别测定根和叶中K~+、Na~+含量,探讨复盐胁迫下2种结缕草K~+、Na~+吸收与运输特点。结果表明:随着盐胁迫浓度的增加,2种结缕草根和叶中Na~+的含量逐渐升高,中华结缕草的Na~+含量大于大穗结缕草;2种结缕草根和叶中K~+的含量呈现不同的变化趋势,根中2种结缕草K~+含量先增加后降低,但大穗结缕草K~+含量增加较大,叶中2种结缕草K~+含量总体呈现增加的趋势。2种结缕草根和叶片中K~+/Na~+随盐浓度增加而逐渐降低,但叶片中K~+/Na~+大于根中K~+/Na~+,表明盐胁迫促进了K~+向叶片运输。大穗结缕草的SK,Na逐渐降低,中华结缕草的SK,Na先降低后升高,说明2种结缕草对K~+和Na~+的选择性运输特点不同。     

Improved Cold and Drought Tolerance of Doubled Haploid Maize Plants Selected for Resistance to Prooxidant tert‐Butyl Hydroperoxide

To improve the abiotic stress tolerance of maize (Zea mays L.), doubled haploid (DH) plants were produced by in vitro selection of microspores exposed to tert‐butyl hydroperoxide (t‐BuOOH) as a powerful prooxidant This study investigated the tolerance of the progenies of t‐BuOOH‐selected DH lines to oxidative stress, cold and drought in controlled environment pot experiments by analyses of photosynthetic electron transport and CO₂ assimilation processes, chlorophyll bleaching and lipid peroxidation of leaves. Our results demonstrated that the t‐BuOOH‐selected DH plants exhibited enhanced tolerance not only to oxidative stress‐induced by t‐BuOOH but also to cold and drought stresses. In addition, they showed elevated activities of antioxidant enzymes such as superoxide dismutase, ascorbate peroxidase, catalase, glutathione reductase and glutathione S‐transferase when compared with the DH lines derived from microspores that were not exposed to t‐BuOOH and to the original hybrid plants. The results suggest that the simultaneous up‐regulation of several antioxidant enzymes may contribute to the oxidative and cold stress tolerance of the t‐BuOOH‐selected DH lines, and that the in vitro microspore selection represents a potential way to improve abiotic stress tolerance in maize.