氮响应转录因子Zm NLP5影响玉米根系生长的功能研究

研究作物氮高效机制并挖掘利用其中重要的调控基因,对我国农业绿色发展具有重要意义。前期我们发现氮响应转录因子ZmNLP5调控亚硝酸还原酶基因的表达,对玉米氮素吸收利用具有促进作用,但其调控机制尚未明确。基于此,本研究以ZmNLP5基因突变体(zmnlp5)和野生型(WT)植株为研究材料,深入解析ZmNLP5影响玉米氮素吸收利用的生理机制。足氮(sufficient nitrogen, SN)和低氮(deficient nitrogen, DN)条件下研究材料表型分析发现, DN条件下相对于WT植株, zmnlp5植株根长显著降低。根部不同区域ZmNLP5表达量分析发现, ZmNLP5主要在根尖区域表达。不同亚硝酸盐浓度处理下,研究材料的根长和根尖区域亚硝酸盐含量分析发现,当亚硝酸盐的浓度高于2mmol L~(-1)时,zmnlp5突变体根长相对于WT显著降低,zmnlp5植株根尖区域亚硝酸盐积累量显著高于WT。SN和DN条件下研究材料根部亚硝酸盐含量检测发现, DN条件zmnlp5植株根尖区域所积累的亚硝酸盐也显著高于WT。综上所述,转录因子ZmNLP5在玉米植株响应低氮环境根部伸长生长中发挥重要功能,该结果为玉米氮高效育种提供了一定的理论基础。     

三维扫描技术在获取杨树树冠结构特征参数上的应用

【目的】树冠结构影响光能截获能力从而直接影响生物量的积累。杨树冠形特征参数的研究能够为杨树优良品种的选育提供有力的选择依据，但是因为杨树的树型高达，树冠结构复杂，树冠结构特征参数难以直接观测。【方法】建立了利用三维扫描技术获取树冠结构特征参数的方法，并测量了高密度(2 m ×3 m)人工林中6年生杨树03-04-171的冠形特征参数，包括不同生长单元早发枝和同期枝一级枝的枝长、分枝角度、方位角、枝条曲率及弯曲度。对直接测量(砍伐)与三维扫描方法测量的胸径、树高进行回归分析，检测三维扫描测量的精度。【结果】回归分析结果表明：胸径的回归系数分别为 R2=0.96772，显著值为 P =8.26×10－13，树高回归系数为 R2=0.96527，显著值为 P=1.44029×10－12。结果说明三维扫描方法具有较高的测量精度，可以应用于树冠结构特征的测量。扫描参数结果显示，树冠上每一个生长单元的上部枝条长度较长，分枝角度较小，曲率较大，数量少，为早发枝；中下部枝条数量多，短而平直，为同期枝，这与已有的研究结果一致。【结论】三维扫描技术可以应用于树冠结构特征的研究。     

Assessing the effect of broadleaf woodland expansion on acidic dry deposition and streamwater acidification

The study aim was to determine whether enhanced dry deposition of acidic atmospheric pollutants by broadleaf woodland expansion could increase the potential for acidification of surface waters in acid-sensitive areas. Dry sulphur (S) and nitrogen (N) deposition was modelled with the Fine Resolution Atmospheric Multi-pollutant Exchange (FRAME) model using a roughness length value calculated specifically for birchwoods. Two scenarios were investigated for an acid-sensitive area in Scotland where broadleaf woodland expansion, mainly as birchwood, is occurring: (1) 2002 emissions and broadleaf woodland cover of 5.6%; (2) 2020 projected emissions and broadleaf cover of 29%. The roughness length calculated for birch with Raupach’s simplified drag-partition model was 0.73 m, lower than the value of 1.0 m for conifers which is the default for forest land cover in FRAME. Modelled dry S and N deposition increased between 2002 and 2020 from 8.7 to 29 × 10⁻³ keq ha⁻¹ year⁻¹ of H⁺. However, modelled total dry and wet non-marine S and N deposition decreased during the same period from 1070 to 682 × 10⁻³ keq ha⁻¹ year⁻¹ of H⁺ due to the lower projected emissions in 2020 and the dominance of wet deposition in the remote and upland study area (mean annual rainfall 2275 mm). The modelled total non-marine S and N deposition was used to calculate streamwater critical loads exceedance with the First-order Acidity Balance (FAB) model for five catchments in the study area. The modelled deposition for both the 2002 and 2020 scenarios was less than the calculated streamwater critical loads so the catchments were not considered at risk of streamwater acidification under the projected future emissions and increased broadleaf woodland cover. Nevertheless, broadleaf expansion could pose a greater risk of acidification in acid-sensitive areas with lower rainfall, closer to pollutant sources, where dry deposition accounts for a higher proportion of total S and N deposition.     

Increased utilization of lengthening growing season and warming temperatures by adjusting sowing dates and cultivar selection for spring maize in Northeast China

Global warming has lengthened the theoretical growing season of spring maize in Northeast China (NEC), and the temperatures during the growing season have increased. In practise, crop producers adjust sowing dates and alternate crop cultivars to take advantage of the lengthening growing season and increasing temperatures. In this study, we used crop data and daily weather data for 1981–2007 at five locations in NEC to quantify the utilization of the lengthening growing season and increasing temperatures by adjusting sowing dates and cultivar selection for spring maize production. If these two positive factors are not fully utilized, then it is important to know the potential impacts of these climatic trends on spring maize grain yields. The results show that in NEC, both the actual and theoretical growing seasons are lengthening, i.e., the sowing dates have been advanced and the maturity dates have been delayed. The actual sowing dates are 1–8 days later and the actual maturity dates are 6–22 days earlier than the theoretical perspective. Advancing sowing dates and changing cultivars led to 0–5 days and 6–26 days extension of the growing season. For the potential thermal time (TT), adjusting the sowing dates decreased the unutilized TT before sowing, while the cultivar selection increased the utilized TT and decreased the unutilized TT after maturity. On average, the unutilized heating resource before sowing is less than that after the maturity date (0.3–1.9% vs. 2.1–7.8%). During 1981–2007, for per day extension of the growing season, the spring maize grain yield increased by 75.2 kg ha⁻¹. The spring maize grain yields have increased by 7.1–57.2% when both early sowing and changing cultivars during 1981–2007. In particular, adjusting the sowing dates increased the grain yield by 1.1–7.3%, which was far less than the increase effect (6.5–43.7%) from switching to late maturing cultivars. Therefore, selecting late maturing cultivars is an important technique to improve maize grain yields in NEC under the global warming context. Nevertheless, if the currently unutilized TT were fully explored, the local spring maize grain yield would have increased by 12.0–38.4%.     

全混合日粮饲喂泌乳奶牛群摄入养分偏离的原因分析及对生产性能的影响

本试验旨在研究全混合日粮(TMR)饲喂泌乳奶牛群摄入养分偏离的原因分析及对生产性能的影响。选取30个高产牛群,每个牛群采样5 d。采取牛群TMR及剩料样品,进行养分分析和颗粒分级评定,计算各指标的变异系数。记录产奶量,取奶样测乳成分。多元线性回归分析养分、颗粒的变异系数与牛群生产性能的关系。结果表明:30个牛群饲喂的TMR产奶净能(NEL)和粗蛋白质(CP)、中性洗涤纤维(NDF)、酸性洗涤纤维(ADF)、微生物蛋白质(MCP)、瘤胃非降解蛋白质(RUP)、瘤胃能氮平衡(RENB)、小肠可消化粗蛋白质(DCPSI)、钙(Ca)含量分别为6.56 MJ/kg和16.22%、35.71%、21.38%、77.84 g/kg、92.15 g/kg、14.77 g/kg、104.04 g/kg、1.43%,其中高于配方目标的指标有NDF(1.94%)、Ca(0.57%)、RUP(5.03 g/kg)、RENB(6.95 g/kg),低于配方目标的指标有CP(-0.36%)、ADF(-1.54%)、NEL(-0.12 MJ/kg)、MCP(-7.71 g/kg)、DCPSI(-2.12 g/kg)(正值表示提高,负值表示降低)。观测期内,RUP[(16.26±7.10)%]、MCP[(22.78±13.38)%]、RENB[(64.29±34.29)%]3种养分的变异系数大于10%,其他养分的变异系数均小于10%。长、中、短、细4类颗粒含量的变异系数分别为(15.78±9.25)%、(9.12±7.86)%、(6.00±4.00)%、(11.15±9.62)%。回归分析表明,TM R养分和颗粒度变异影响产奶量和乳成分,NEL变异系数每升高1个百分点,产奶量下降3.662 kg/d;长颗粒变异系数每升高1个百分点,产奶量下降0.124 kg/d,乳脂率升高0.012%。结果提示,TMR饲喂泌乳奶牛摄入养分因投料不准确、加工质量不稳定、搅拌不均匀、挑食等与配方养分产生差异。TMR加工质量稳定性影响到产奶量和乳成分,其中NEL、DCPSI、RENB的变异影响产奶量,长颗粒变异影响产奶量和乳脂率。     

二郎山山地鸡鸡距生长测定及分析

本试验以二郎山山地鸡为研究对象,分析其2个品系鸡距的生长发育规律,希望能将其鸡距的长度作为区分两品系的标志之一。本试验从23周龄开始,每个品系测定100只公鸡的距长,每周测1次(第1阶段),结果发现,同一品系中4次测定结果均差异不显著(P0.05);从27周龄开始,改为每个月测1次(第2阶段),结果表明:2个品系的距长发育整齐度并不是很高,距长与个体发育有关,与生长时间不呈绝对正比,且与体重不相关(R0.3);SD03系公鸡的距明显长于SD02系(P0.05)。试验结果表明,可以将距长作为区分2个品系的标志之一,但在实际生产中该方法对饲养时间较短的商品肉鸡不可行。     

NaCl胁迫对3种草地早熟禾种子萌发特性的影响

用室内模拟的方法,对"午夜""新歌来德""抢手股"3种草地早熟禾种子进行4种不同浓度(0、1、1.5、2mmol·L-1)的NaCl溶液盐胁迫试验,结果表明:盐浓度越高,植物受到的盐胁迫越大;3种早熟禾种子中,发芽率、胚根长度和胚芽长度最高的均为午夜种子,最低的为抢手股种子。午夜种子的综合能力较强,最适合应用于抗盐碱土地中,新歌来德次之,而抢手股不适合种植在盐碱地中。     

Effects of plant roots on soil preferential pathways and soil matrix in forest ecosystems

To characterize effects of plant roots on preferential flow(PF),we measured root length density(RLD)and root biomass(RB) in Jiufeng National Forest Park,Beijing,China.Comparisons were made for RLD and RB between soil preferential pathways and soil matrices.RLD and RB declined with the increasing soil depth(0–10,10–20,20–30,30–40,40–50,50–60 cm) in all experimental plots.RLD was greater in soil preferential pathways than in the surrounding soil matrix and was 69.5,75.0 and72.2 % for plant roots of diameter(d) \1,1 \ d \ 3 and3 \ d \ 5 mm,respectively.Fine root systems had the most pivotal influence on soil preferential flow in this forest ecosystem.In all experimental plots,RB content was the sum of RB from soil preferential pathways and the soil matrix in each soil depth.With respect to 6 soil depth gradient(0–10,10–20,20–30,30–40,40–50,50–60 cm) in each plot,the number of soil depth gradient that RB content was greater in soil preferential pathways than in the soil matrix was characterized,and the proportion was68.2 % in all plots.     

红松、蒙古栎和色木槭凋落物混合分解研究

以位于中国东北吉林蛟河的天然红松阔叶林森林生态系统为研究对象,针对其中主要树种的凋落物分解速 率和分解过程研究中的几个关键问题进行了探讨。研究内容包括该生态系统中常见的红松、蒙古栎和色木槭的凋 落物的分解速率,在分解过程中的养分动态和凋落物的混合效应及其机制等。本研究使用的具体方法为凋落物降 解袋法。结果表明:1)凋落物中各种营养元素的初始含量差异显著,其中初始氮、磷含量与凋落物的分解速率呈正 相关。2)不同树种凋落物的失重率之间差异显著,且均随时间进程增大,但是和时间不成线性关系。3)在整个分 解进程中,凋落物的分解速率开始时明显升高,中后期以后逐渐平稳。4)单一凋落物分解中,阔叶凋落物的分解速 率高于针叶的分解速率。5)395 d 的分解进程中,有机碳(C)、全氮(N)、全磷(P)、全钾(K)含量呈动态变化, N 和 P 均表现出富集现象,N 在短期富集后强烈释放;C 和K 表现为净释放;C/ N 持续下降。6)红松 蒙古栎和红松 色 木槭混合凋落物对分解速率产生显著的混合效应; 混合凋落物对分解过程中的养分动态, 尤其是P 和N 元素具有 显著的混合效应, 而混合效应的方向(正或负)和强度是十分复杂的;混合效应是否能发生及其发生的方向主要是 由组分凋落物的特点来决定的。