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991.
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[目的]为明确枣棉间作模式下不同施氮量对棉花根际微生物的影响。[方法]通过田间小区试验,研究0、150、300、450、600、750 kg/hm26种施氮水平对枣树‖棉花模式中棉花根际土壤中细菌、真菌和放线菌数量的变化动态。[结果]300和450 kg/hm2施氮量能显著增加蕾期、花期和吐絮期微生物总数量。细菌和放线菌在整个生育期中蕾期数量最少,铃期和花期较高,吐絮期次之。真菌数量各个时期变化不大。适宜施氮量能增加铃期枣棉间作交际行棉花根际土微生物数量。[结论]该研究可为枣棉间作系统合理施用氮肥提供科学依据。 相似文献
994.
995.
Differential Responses of Nitrifier and Denitrifier to Dicyandiamide in Short- and Long-Term Intensive Vegetable Cultivation Soils 总被引:1,自引:0,他引:1
Nitrification inhibitors, such as dicyandiamide (DCD), have been shown to decrease leaching from urea- and ammoniumbased fertilizers in agricultural soils. The effect of nitrification inhibitors on nitrifier and denitrifier in short- and long-term intensive vegetable cultivation soils was poorly understood. In this study, the pot trial was conducted to investigate the differential responses of nitrifier (amoA-containing bacteria) and denitrifier (nirK-containing bacteria) to DCD in short-(soil S) and long-term (soil L) intensive vegetable cultivation soils. Quantitative polymerase chain reaction (qPCR) and terminal restriction fragment length polymorphism (T-RFLP) were employed to detect the abundance and composition of amoA- and nirK-containing communities. The results indicated that application of DCD led to a consistently higher NH4+-N concentration during the whole incubation in soil L, while it was quickly decreased in soil S after 21 days. Furthermore, DCD induced more severe decrease of the abundance of amoA-containing bacteria in soil L than in soil S. However, the abundance of the nirK- containing community was not significantly affected by DCD in both soils. Long-term vegetable cultivation resulted in a super-dominant amoA-containing bacteria group and less divergence in soil L compared with soil S, and DCD did not cause obvious shifts of the composition of ammonia-oxidising bacteria (AOB). On the contrary, both amoA- and nirK-containing bacterial compositions were influenced by DCD in soil S. The results suggested that long-term intensive vegetable cultivation with heavy nitrogen fertilization resulted in significant shifts of AOB community, and this community was sensitive to DCD, but denitrifiers were not clearly affected by DCD. 相似文献
996.
LIU Guo-qing ;LIAN Ying-qi ;GAO Chao ;YU Xiao-feng ;ZHU Ming ;ZONG Kai ;CHEN Xue-jiao ;YAN Yi 《中国农业科学(英文版)》2014,(5):1121-1129
Aptamers are specific nucleic acid sequences that can bind to a wide range of nucleic acid and non-nucleic acid targets with high affinity and specificity. Nucleic acid aptamers are selected in vitro from single stranded DNA or RNA ligands containing random sequences of up to a few hundred nucleotides. Systematic evolution of ligands by exponential enrichment (SELEX) was used to select and PCR amplify DNA sequences (aptamers) capable of binding to and detecting Listeria monocytogenes, one of the major food-borne pathogens. A simplified affinity separation approach was employed, in which L. monocytogenes in exponential (log) phase of growth was used as the separation target. A fluorescently-labeled aptamer assay scheme was devised for detecting L. monoeytogenes. This report described a novel approach to the detection of L. monocytogenes using DNA aptamers. Aptamers were developed by nine rounds of SELEX. A high affinity aptamer was successfully selected from the initial random DNA pool, and its secondary structure was also investigated. One of aptamers named e01 with the highest affinity was further tested in aptamer-peroxidase and aptamer-fluorescence staining protocols. This study has proved the principle that the whole-cell SELEX could be a promising technique to design aptamer-based molecular probes for dectection of pathogenic microorganisms without tedious isolation and purification of complex markers or targets. 相似文献
997.
MA Dong-yun SUN De-xiang ZUO Yi WANG Chen-yang ZHU Yun-ji GUO Tian-cai 《中国农业科学(英文版)》2014,(6):1258-1267
The current interest in the health beneifts of whole wheat grain has prompted breeders to further increase the concentration of antioxidants in wheat. The objective of this study was to investigate the variation in antioxidant content among Chinese wheat grains and the relationship between antioxidants and grain color and morphological characteristics. A wide variation was observed in the total phenolic, carotenoid and lfavonoid contents, as well as the antioxidant activity (AOA), of Chinese wheat varieties. Black wheat had the highest mean total phenolic, carotenoid and lfavonoid contents and the highest AOA, followed by red and white wheats. The grain color parameters were signiifcantly negatively correlated with total phenolic, carotenoid and lfavonoid contents and AOA among all of the wheat varieties examined, and grain weight was also signiifcantly negatively correlated with these traits. The same correlation between grain weight and antioxidant traits was also observed within individual groups of wheat, which indicates that grain weight may be used as an index for selecting wheat varieties with high AOA. Landraces had signiifcantly higher lfavonoid content than commercial wheat varieties. The results of this study may be useful for breeding nutrient-rich wheat varieties. 相似文献
998.
建设用地供应是一个庞大而又复杂的系统,不仅仅是土地本身的问题,同时还与人口、社会、经济、政治等因素紧密相关。合理的建设用地供应不但能够促进土地集约利用、保护耕地,而且能够改善城乡居民生产生活条件、促进产业结构调整、拉动区域经济发展。基于此认识,根据长沙市1995~2013年统计数据,运用Eviews6.0软件,通过单位根检验、协整检验、Granger因果关系检验探讨建设用地供应与经济社会发展间的相关关系,重点探讨建设用地与GDP、城市化率的关系。结果表明:建设用地供应与GDP之间存在双向因果关系,而与城市化率之间只有单向因果关系。 相似文献
999.
1000.
[目的]对几种SDS-PAGE凝胶电泳染色方法进行比较。[方法]从凝胶背景颜色、染色时间及灵敏度的角度对6种SDS-PAGE凝胶电泳快速染脱色方法进行比较研究,并对适用于椰子和油棕总蛋白质SDS-PAGE凝胶电泳的实用方法进行总结。[结果]方法 F最快速,条带清晰,染料及试剂都较少,是一种经济、快速、安全、实用的染色方法,整个过程仅需1 h左右。[结论]试验比较了几种SDSPAGE凝胶电泳染色方法,对进一步开展椰子和油棕蛋白质组学研究具有重要意义。 相似文献