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241.
242.
以含nisZ基因的质粒pHJ201为模板,对乳链菌肽铰链区进行定点突变,并以pMG36e为载体,转入受体菌L.lactis NZ9800进行表达,研究不同电荷铰链区突变体的特性及结构。结果表明,9个突变体中除N 20En is in Z,M21E nisinZ和K22E n is in Z失去抑菌活性外,其余突变体的抑菌活性均有下降;N20K nisinZ和M21KnisinZ突变体的抑菌谱发生了变化,其对革兰氏阴性菌沙门氏菌、志贺氏菌和假单胞菌均有抑菌活性。CD谱表明,在波长210~220 nm区,N 20K nisinZ和M21KnisinZ的-αhelix值均较野生型nisinZ略有提高。 相似文献
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垂直航空摄影像片上存在的投影差,使得坡向向像主点的坡长影像相对延长,逆像主点的坡长影像相对缩短,这在高差大、坡向变化频繁的山区更为显著。当坡长影像长度小子于其理论影像长度的2/3时,坡面上的各地类界线难以判清;小于1/2时,则坡面上的许多地类都难以判出。因此,以像主点为中心的航片最适有效作业半径r_1≤- H_A/2h D_1=f/3tgα,极限有效作业半径rm=- H_A/h D_1=f/2tgα,即最适和极限有效作业半径决定于逆向坡高差h的负值和坡长影像长度D_1或地面倾角α。 相似文献
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246.
Organic residues affect phosphorus availability and maize yields in a Nitisol of western Kenya 总被引:3,自引:0,他引:3
The effects of organic residues and inorganic fertilizers on P availability and maize yield were compared in a Nitisol of
western Kenya. Leaf biomass of Calliandra calothyrsus, Senna spectabilis, Croton megalocarpus, Lantana camara, Sesbania sesban, and Tithonia diversifolia were incorporated into the soil at 5 Mg ha–1 for six consecutive seasons in 3 years and responses compared with those following the application of 120 kg N ha–1, 0 kg P ha–1 (0P); 120 kg N ha–1, 10 kg P ha–1; and 120 kg N ha–1 25 kg P ha–1 as urea and triple superphosphate (TSP); K was supplied in all treatments. Addition of Tithonia, Lantana and Croton increased soil resin-extractable P over that of fertilizer-amended soil throughout the first crop, but the amounts in the
former treatments became similar to those for soils amended with inorganic fertilizers for subsequent crops. Addition of Sesbania, Calliandra and Senna had a similar effect on resin P as inorganic fertilizers. Total maize yields after six seasons were tripled by the application
of Tithonia compared to 0P, and were higher than those of the Calliandra, Senna, Sesbania and Lantana treatments, and similar only to that of the Croton treatment. P recovered in the above-ground biomass and resin P, immediately after the implementation of the treatments, was
higher in the Senna, Sesbania, Croton, Lantana and Tithonia (35–77%) treatments than in the inorganic fertilizer treatments (21–27%). The P content of organic residues, and the soluble
C:total P ratio, were the main residue parameters predicting soil P availability and maize yield. All organic residues used
in this study can replace inorganic fertilizers for the enhancement of P availability and maize production, while an additional
benefit could be obtained from the use of Croton, Lantana and Tithonia.
Received: 19 January 2000 相似文献
247.
山西瘦肉型猪SD-Ⅱ系繁殖性状的表型和遗传参数估测 总被引:2,自引:0,他引:2
本文对山西瘦肉型猪SD—Ⅱ系繁殖性状的表型参数和遗传参数进行了研究 ,结果如下 :(1)繁殖性状存在负的母体效应 ,表型变化不稳定 (呈亲代高子代低 ,亲代低子代高的趋势 ) ,不适宜用表型选择进行选择 ;(2 )总产仔数、活产仔数、初生窝重、初生个体平均重、泌乳力、断奶窝重、断奶个体平均重、断奶头数、总乳头数的遗传力分别为 0 2 30、 0 2 42、 0 2 19、 0 2 5 7、 0 184、 0 12 8、 0 40 8、 0 419、 0 5 0 2 ,与国内文献报道结果相近 ,而高于国外文献报道结果。 (3)繁殖性状间的遗传相关都比较强 ,断奶头数与大多数繁殖性状的遗传相关呈显著或极显著的正相关 ,因此应作为繁殖性状的主选性状之一 相似文献
248.
Late blight (LB), caused by Phytophthora infestans, is one of the most devastating diseases of tomato (Solanum lycopersicum) worldwide. Aggressive pathogen isolates resistant to fungicides have driven research in favour of finding new sources of host resistance for tomato breeding. Recently, we reported S. pimpinellifolium accession PI 270443 exhibiting LB resistance stronger than all commercial LB-resistant tomato cultivars. The purpose of this study was to examine the inheritance of LB resistance conferred by this accession. An interspecific cross was made between PI 270443 and a LB-susceptible tomato breeding line and advanced to F10 generation. A total of 166 F9 and corresponding F10 recombinant inbred lines (RILs) were evaluated for response to LB in four replicated greenhouse experiments. Estimates of heritability (h2) of LB resistance, determined by parent–offspring (F9:F10) correlation analysis, ranged from 0.66 to 0.81, with an average of 0.76. The moderately high h2 of LB resistance in PI 270443 suggests the utility of this accession for tomato breeding. Molecular mapping and RNA-sequencing efforts are underway to identify genes underlying LB resistance in PI 270443. 相似文献
249.
【目的】针对柑橘中常用的农药,采用QuEChERS方法和超高效液相色谱-三重四极杆串联质谱,系统研究了其测定过程中的基质效应。【方法】柑橘样品利用乙酸-乙腈溶液(V∶V=1∶99)提取、GCB净化,采用甲醇-0.1%甲酸水溶液(含1 mmol·L-1乙酸铵)作为流动相,正离子多反应监测(MRM)模式,基质外标法定量,可以有效地减弱基质效应。【结果】10种农药在柑橘中主要是以基质抑制为主,其基质效应范围为-18%~4%,在0.1~100 ng·mL-1内线性关系良好,相关系数(r)大于0.999,检出限为0.08~0.30μg·kg-1,回收率为70.5%~102%,相对标准偏差(RSD)为3.32%~5.76%。【结论】该方法快速简便、净化效果好,适合柑橘中常见农药的快速测定。 相似文献