The influence of Mg fertilization on growth and mineral contents of fine roots in (Picea abies [Karst] L.) stands at different stages of decline in NE-Bavaria

The effect of various Mg-fertilizers (MgSO₄; calcined dolomite) on root growth and mineral composition of 40 yr old Norway spruce at different sites and stages of decline was studied. Two years after fertilization, density of living fine roots of Mg-deficient trees had significantly increased on fertilized compared to non-fertilized plots. Only fertilization of calcined dolomite appeared to induce new root formation in the upper mineral soil. No such changes were observed for healthy looking trees at a second experimental site, where base saturation of the bulk soil was also low but trees were sufficiently supplied with Mg. At the third experimental site where foliar analyses reflected a luxurious Ca and Mg but an insufficient K nutrition at high Mg and Ca saturation of the bulk soil, calcined dolomite caused an increase of root growth due to a reinforced antagonism between Ca and Mg competing with K uptake. In general, at the experimental sites the fine root necromass decreased when base saturation of the bulk soil increased. The elemental contents of fine roots from the minenal soil of all three sites under investigation indicated that fine root growth in the mineral soil is strongly related to the root Ca and Mg contents. Root Ca contents seemed to be mainly a function of the Ca availability in the soil. Since there was no close relationship between fine root growth and the Ca/Al molar ratio in living fine roots, Al toxicity may not completely account for the differences in root growth and nutrition on the experimental sites.     

Determination of carbadox-related residues in swine liver by gas chromatography/mass spectrometry with ion trap detection

The ion trap detector (ITD), in combination with a capillary gas chromatograph and under chemical ionization conditions, offers sufficient sensitivity to determine carbadox-related residues as the methyl ester derivative of quinoxaline-2-carboxylic acid at 3 micrograms/kg or higher in porcine liver. A tetradeuterated internal standard of QME effectively compensates for losses incurred during sample preparation. The method produced mean levels of 3.3 (+/- 0.5), 5.5 (+/- 0.8), and 10.1 (+/- 0.9) micrograms/kg for liver fortified at 3, 5, and 10 micrograms/kg. When applied to analysis of samples containing incurred residues of 14C-carbadox at the low microgram/kg level, results were comparable to those obtained by reverse isotope dilution analysis.     

The effects of protein level on cytokines and chemokines in the uterine environment of beef heifers during development

The development of replacement heifers is crucial for breeding success and herd efficiency. Nutritional management can affect not only reproductive development but also the inflammatory status of the uterine environment, which may impact reproductive functions such as pregnancy establishment and development. The study herein evaluated the concentration of cytokines and chemokines in the uterus of heifers supplemented with different levels of protein. Angus heifers (n = 60) were blocked by body weight (BW) and randomly assigned to 1 of 3 treatments based on protein supplementation level: control of 10% crude protein (CON), 20% crude protein (P20), or 40% crude protein (P40). BW, body condition score, and blood samples were taken every 2 wk for 140 d to monitor development. Uterine flushes were performed monthly and concentrations of cytokines (IL-1α, IL-1β, TNF-α, IFN-γ, IL-10, VEGF-α, IL-17A, and IL-36RA) and chemokines (IL-8, MCP-1, MIP-1α, and MIP-1β) were quantified via ELISA multiplex. To test if there were mean differences in cytokines between the treatment groups or over time, PROC GLIMMIX (SAS v 9.4) was utilized. Concentrations of all cytokines and chemokines, except IL-1α, changed throughout heifer development (P < 0.05). Heifers in the P40 treatment group displayed reduced concentrations of MCP-1 (P = 0.007) and tended to have decreased concentrations of IFN-γ (P = 0.06). Cytokine IL-36RA tended (P = 0.06) to be affected by protein level, with the lowest concentrations observed in CON heifers. Most cytokines and chemokines increased following the initial month of supplementation (P < 0.05). The increase in concentrations after 1 mo may indicate an adaptive response in the uterus to diet change. Cytokines and chemokines fluctuated due to physiological changes occurring during development. Further research is needed to determine the influence of nutrition on uterine inflammation and long-term impacts on reproductive function.     

青海省干旱灾害时间序列分形特征研究

采用标度变换法,计算了1470—1970年青海省总体干旱灾害、各等级旱灾及旱季序列的时间分维数,并探讨了各等级旱灾及旱季序列时间分维的动态变化特征。结果表明,干旱灾害时间序列存在自相似性,具有分形特征。各等级旱灾以及各旱季时间分维数与其发生频次正相关。不同等级干旱灾害的时间重演规律不同,旱灾程度越重,无标度区越宽、分维值越低;旱灾程度越轻,无标度区越窄、分维值越高。旱灾序列时间分维数与区域气候条件有关。研究时段内,总体旱灾和轻度旱灾的发生趋向混沌无序化,短周期更加明显;中度旱灾变化较无序;春旱趋向混沌无序的平衡态,夏旱则出现短周期与长周期、有序与无序的交替现象。     

基于人工神经网络的黑龙江省农机总动力预测

黑龙江省农机总动力的建模和预测是制定黑龙江省农机发展计划的重要依据。为此,应用BP人工神经网络技术(BP-ANN)处理1980～1998年农机总动力数据,建立正确的预测模型。利用此模型预测出1999～2003年黑龙江省农机总动力数值,预测结果和实际结果有很好的一致性;同时,预测了2004～2006年黑龙江省农机总动力数值,为今后制定农机发展战略提供参考依据。     

高丹草遗传效应与杂种表现预测模型

以5个高粱不育系材料为母本, 18个优质苏丹草材料为父本, 按照遗传交配设计(NCII)配制成90个杂交组合。分别在内蒙呼市和包头两地, 利用与高丹草产量相关的QTL位点标记检测亲本间的遗传差异, 并将F₁的8个性状表型值对亲本材料进行标记位点的筛选, 建立标记效应和标记型值估算体系。估算特异性位点对性状表现的效应及杂种标记型值, 进而分析杂种标记型值与杂种表现的相关性, 应用逐步回归分析法建立8个性状杂种表现的预测模型, 并通过Jackknife抽样技术检测模型的精确度和稳定性。结果显示, 在分别考虑显性、加性作用下8个性状的标记型值与表型值的相关系数平均为0.65, 各性状的可决系数较大(0.51~0.88), 而且两地结果趋势一致, 表明该预测模型稳定性强, 精确度较高。该模型对高丹草的杂种表现预测以及亲本选配都具有一定的指导意义。     

用SSR标记建立玉米黄早四DNA标准指纹图谱的方法研究

DNA标准指纹图谱是分子检测技术用于玉米新品种选育及其DUS辅助评价的重要基础。通过玉米对黄早四DNA的SSR标准指纹图谱构建方法的研究,筛选出20对可以用于玉米DNA标准图谱构建的核心引物,它们的平均PIC值为0.8554,检测出的等位基因数是6~15个,平均8.55个,Bnlg125和Bnlg2162检测到了玉米黄早四的DNA特有谱带;8%的聚丙烯酰胺电泳体系可以将亲缘关系很近的玉米品种区分开来。对玉米DNA标准指纹图谱的建立方法和DNA取样方法进行了深入探讨。     

Satellite-like particle of tobacco ringspot virus that resembles tobacco ringspot virus

A satellite-like nucleoprotein serologically indistinguishable from multicomponent tobacco ringspot virus, also resembles it in size, shape, and electrophoretic mobility. Although the protein shell of the nucleoprotein is similar to, if not identical to that of tobacco ringspot virus, each ahell of the nucleoprotein conntains many small strands of nucleic acid, which replicate only in mixed infections with the virus.     

7个茶树品种的花粉形态与生活力研究

为研究不同茶树品种之间花粉的形态特征与生活力变化,以7个茶树品种为试材,进行花粉形态结构观察及其随培养时间增长萌发率的变化趋势研究。结果表明:(1)7个茶树品种花粉均呈左右对称,具有3个萌发沟,长度和宽度差异不显著,萌发沟长度、宽度以及延伸比例呈现多样性,赤道面观呈椭圆形和棱锥形,极面观呈圆形和近三角形;外壁呈现光滑瘤状和粗糙瘤状,且部分品种花粉表面有穿孔。(2)在24 h的培养时间内,7个茶树品种的花粉萌发率均呈"S"型曲线增长,且基本上在1、3和5 h呈现显著性差异增长,到7 h接近萌发峰值。其中,柿大茶黄种、龙井43、福鼎大白茶的花粉萌发率较高,而云抗10号的花粉萌发率均显著低于其他6个品种。对中国种舒茶早(Camellia sinensis var. sinensis ‘Shuchazao’)与阿萨姆种云抗10号(Camellia sinensis var. assamica ‘Yunkang 10’)的花粉在不同贮藏条件下的生活力进行进一步的比较,发现它们在4℃和–20℃温度下的生活力存在显著差异,在180d的贮藏时间内,舒茶早与云抗10号分别在–80℃与–20℃的贮藏温度下对其花粉活力的保存更适宜。