箬叶总黄酮提取方法的研究

分别用水浴和超声2种方法提取箬叶中的总黄酮。通过单因素水平试验和正交试验,确定最佳浸提剂为乙醇;水浴最佳提取条件:乙醇体积分数85%,回流时间3h,液-固比20:1,水浴温度85℃;超声最佳提取条件:乙醇体积分数85%,超声时间30min,液-固比20:1;且超声方法优于水浴方法。在最佳提取条件下,测定箬叶总黄酮含量,冬季采摘的叶为1.92%,夏季采摘的叶为1.38%。     

加强甜玉米鲜食期籽粒品质变化研究

研究加强甜玉米和普通玉米2种不同类型玉米鲜食期籽粒品质变化，以明确各品质变化的动态规律。试验采用不同基因型的玉米材料，测定果穗鲜食期可溶性总糖含量、水分含量、蛋白质含量和百粒鲜重，并进行相关分析。结果表明：鲜食期籽粒发育过程中加强甜玉米可溶性总糖含量和积累速度高于普通玉米；水分的下降速度加强甜玉米比普通玉米慢；蛋白质含量加强甜玉米略低于普通玉米，蛋白质的积累与籽粒鲜重的增加过程基本一致；鲜粒重积累速度加强甜玉米低于普通玉米；授粉13d和授粉28d加强甜玉米和普通玉米蛋白质含量和鲜粒重都相近。     

超高压对腌鱼保藏的影响

以淡腌海鳗为对象,采用200、400、600 MPa处理15 min,通过挥发性盐基氮、三甲胺、总活菌数、硫代巴比妥酸值和pH值等在保藏过程的变化考察超高压对腌鱼保藏的影响.结果表明,600 MPa处理可以极大地抑制微生物生长和脂肪氧化,降低挥发性盐基氮、三甲胺.说明超高压是一种较好的适合腌鱼保藏的冷杀菌技术.     

氮钾肥对污染土壤中蕹菜生长及吸收铅的影响

为了探索提高植物吸收铅(Pb)的能力及增加铅迁移量的方法,采用温室盆栽试验,研究了单施氮钾(N、K)肥及配合施用对蕹菜生长及吸收铅的影响。结果表明:土壤铅浓度为500mg/kg条件下,单施氮肥、钾肥与低量氮肥配施能显著增加植物地上部生物量,提高植物地上部铅的含量,进而显著提高了植物的铅迁移总量,其中以低量氮肥与高量钾肥配合施用的效果最好,单施钾肥则降低植株的铅迁移总量;单施氮肥及氮钾肥适当比例配施还可以提高植物地上部铅的迁移量,提高植物地上部提取铅的效率。因此,通过调节土壤氮钾营养的方法可以提高铅污染土壤中植物对铅的吸收能力及迁移总量。     

不同方法提取狗脊蕨叶片总RNA的比较分析

[目的]为构建狗脊蕨叶cDNA文库,保存珍贵基因资源,克隆和研究与有效成分合成相关的基因等提供技术参考。[方法]以狗脊蕨叶片为材料,采用CTAB法、一步法、酚-SDS法和RNA试剂盒提取分离法提取总RNA,通过比较分析确定最优方法。[结果]这4种方法都能提取出182、8 S的RNA,但CTAB法和试剂盒提取分离法的总RNA质量较高,CTAB法还提取出清晰的5S RNA。一步法和SDS法带型模糊,有降解现象。CTAB法提取的狗脊蕨叶片总RNA质量较好,28S1、8S和5S条带清晰,且无明显降解。CTAB提取法OD260/OD280的值在1.93~2.06,试验中其OD260/OD280值为2.012,接近2.0,纯度较高。一步法和SDS法OD260/OD280>2.0,试剂盒法OD260/OD280<2.0。[结论]CTAB法适合提取的狗脊蕨叶片总RNA,质量较好,可用于cDNA合成、文库构建等后续分子生物学试验。     

有机无机复合肥在不同发酵时期腐殖质及其组成的动态变化

研究了在有机肥堆制过程中加入一定量的化肥后腐殖酸总量、游离腐殖酸、胡敏酸、富里酸养分形态发生的转化.结果表明,由于微生物的作用,有机质含量快速下降,变温条件下下降的速率快于恒温条件;腐殖酸总量无明显增加,游离腐殖酸和胡敏酸表现出明显的增加趋势,变温条件下增加的速率快于恒温条件;富里酸呈现明显的下降趋势,胡富比增大.     

Characterization of lettuce (Lactuca sativa L.) grown with biopesticides and deltamethrin

The purpose of this study was to evaluate the physico-chemical characteristics and the post-harvest loss of mass of curly lettuce (Lactuca sativa L.) cv. Verônica that was grown in a protective environment with applications of biopesticides. The curly lettuce was treated by spraying with neem oil, cassava flour wastewater (manipueira), biofertiliser or the control treatment of deltamethrin. We determined the weight, circumference, dry matter, ash, crude protein, total phenols and minerals profile for the heads of lettuce. After harvesting, the lettuce was packed into opened plastic bags and kept at 5 °C for 5 days to evaluate its weight loss. No differences were observed among the treatments for the physico-chemical parameters. The lettuce that was sprayed with manipueira or biofertiliser had the greatest weight loss during storage. The achievement of similar yields with cheaper products suggests a benefit of using organic bioinsecticides.     

基于BP神经网络的农机总动力预测

分析了BP神经网络用于预测时存在的不足,进而对基于BP神经网络的时间序列的预测问题进行了探讨.根据BP神经网络结构的特点,依据Z变换理论,提出了这一类预测问题可选用y=x作为传递函数,并分析指出了在BP神经网络中,以y=x作为传递函数与y=a+bx作为传递函数等价的结论,同时指出了网络结构应为两层网络.在此基础上,推导...     

日光温室气象环境综合研究(三)——几种弧型采光屋面温室内直射光量的比较研究

本文计算了北京地区四种弧型采光屋面的温室内10～4月各月平均太阳直接辐射日总量(简称直射光总量),并进行了比较。结果表明10～4月室内直射光总量均以圆面——抛物面组合型温室最高,椭圆面最低。圆面和抛物面相比,冬季(11～2月)前者优于后者,春季(3～4月)相反。     

Fractal features of soil particle size distribution and the implication for indicating desertification

Some of the effects of land desertification on soil properties are manifested by the coarsening of the soil particlesize distribution (PSD) and the losses in organic C and nutrients. The changes and characteristics of PSD and selected chemical properties in soils at the 0-15 cm plough layer from different degrees of desertified croplands are analyzed in the semiarid Horqin Sandy Land, northern China. The fractal dimension of the PSD is emanated to characterize the patterns of PSD. The relationships between the fractal dimension of the PSD and selected soil properties are discussed. The results show that: (1) in the transformation from potential desertified cropland to extremely desertified cropland, the sand content at the 0-15 cm soil increased from 69% to 93%, organic C and total N contents decreased by 65% and 69%, respectively; (2) the fractal dimension of PSD ranged from 2.179 to 2.611, the more the contents of sand, the lower the fractal dimension and the higher the desertified degree of farmland. In the desertification process within the studied area, the mean fractal dimension decreased from 2.555 for the potential desertified soils to 2.298 for extremely desertified soils; (3) there existed considerable linear relationships between fractal dimension and soil properties. It was shown that fractal dimensions of PSD are useful parameters able to monitor soil degradation and to estimate the degree of soil desertification.