一种新的机顶盒缓存控制算法     

彭日回  郑善贤 《湖南农业大学学报(自然科学版)》1999,26(3)

结合视频点播系统中的一种存储与传输技术，分析并介绍了一种机顶盒功能的实现方案，研究了机顶盒视频点播缓存控制问题并提出了一种控制算法。  相似文献   

几种植物生长调控剂对油菜的生物学效应     

宋光泉  欧阳静仁 《仲恺农业技术学院学报》1999,12(3):44-49

以杂交油菜秦油２ 号和普通油菜中油８２１ 为试验材料，研究了在施硼砂的基础上喷施植物生长调控剂对油菜的生物学效应－ 结果表明：喷施多效唑（ＭＥＴ）使油菜叶片的气孔数、有效荚果数大幅度增加，对千粒重影响不明显，但使荚果内的表现粒数明显减少，尤其使秦油２ 号的成棵率极显著降低，且减产达显著水平；喷施８０２ 使油菜的有效荚果数和千粒重增加，但使叶片的气孔数和荚果内的表现粒数减少，增产效果不显著；喷施增产菌除使千粒重有增加的趋势外，但使中油８２１ 的成棵率极显著降低，增产效果也不显著  相似文献   

亚热带山地多年生黑麦草及选育材料生产性能的评价   总被引：5，自引：1，他引：4  

白静仁  李向林 《草业科学》1999,16(4):66-70

在南方亚热带山地，对１２个多年生黑麦草品种和选自老草地上１１个育种材料的生长发育状况观察及生产性能进行了评价和比较，３年的试验结果表明，在该试验条件下表现优良的有来自美国的品种编号为１７－１Ｂｉｓｏｎ和选自老草地上的９１－１，Ｈ－１５和Ｂ－１等３个选育材料，它们的共同特点是返青早，产草量高，有推广前景和继续选育的价值。  相似文献   

Pisatin demethylation by fungal pathogens and nonpathogens of pea: association with pisatin tolerance and virulence     

L. M. DELSERONE  K. McCLUSKEY  D. E. MATTHEWS  H. D. VANETTEN   《Physiological and Molecular Plant Pathology》1999,55(6):317

Previous studies have indicated that detoxification of their hosts' phytoalexins is a tolerance mechanism for some true fungi, but not the fungus-like Oomycota, and may be involved in determining the virulence of a pathogen. In the present study, the associations between demethylation of the pea phytoalexin pisatin, tolerance to pisatin, and virulence on pea were examined for 50 fungal isolates which represent 17 species of pathogens and nonpathogens of pea. All isolates ofPythium coloratum and P. irregulare failed to metabolize and were sensitive to pisatin, consistent with previous observations that members of the Oomycota generally lack the ability to metabolize and are sensitive to their hosts' phytoalexins. Among true fungi tested, the ability to demethylate pisatin was common, regardless of whether the particular isolate was pathogenic on pea or not. However, when the rate of pisatin demethylation was compared to virulence, all but one of the moderate to highly virulent isolates rapidly demethylated pisatin. In addition, the more rapidly demethylating isolates were generally more tolerant of pisatin. These results suggest that a specialized enzyme system for quickly detoxifying pisatin might be present in most pea pathogens. In previous studies a specific cytochrome P450 enzyme for demethylating pisatin was identified in the pea pathogen Nectria haematococca mating population VI, and genes (PDA genes) encoding that enzyme have been cloned from this fungus. When DNA specific for these genes was used to probe genomic DNA from other fungi that demethylate pisatin, significant hybridization was detected with only one fungus, the pea pathogen Fusarium oxysporum f. sp. pisi. If the other pea pathogens possess a specific cytochrome P450 system for detoxification of pisatin, the genes encoding these enzymes apparently share limited nucleotide similarity with N. haematococca PDA genes.  相似文献   

Predicting Carbon Stocks Following Reforestation of Pastures: A Sampling Scenario‐Based Approach for Testing the Utility of Field‐Measured and Remotely Derived Variables     

《Land Degradation \u0026amp; Development》2017,28(3):1122-1133

Reforestation of agricultural lands is an important means of restoring land and sequestering carbon (C). At large scales, the labour and costs of direct measurement of ecosystem responses can be prohibitive, making the development of models valuable. Here, we develop a new sampling scenario‐based modelling approach coupled with Bayesian model averaging to build predictive models for absolute values in mixed‐species woody plantings and differences from their adjacent pasture, for litter stocks, soil C stocks and soil C:N ratios. Modelling scenarios of increasing data availability and effort were tested. These included variables that could be derived without a site visit (e.g. location, climate and management) that were sampled in the adjacent pasture (e.g. soil C and nutrients) or were sampled in the environmental planting (e.g. vegetation, litter properties, soil C and nutrients). The predictive power of models varied considerably among C variables (litter stocks, soil C stocks and soil C:N ratios in tree plantings and their differences to their adjacent pastures) and the model scenarios used. The use of a sampling scenario‐based approach to building predictive models shows promise for monitoring changes in tree plantings, following reforestation. The approach could also be readily adapted to other contexts where sampling effort for predictor variables in models is a major potential limitation to model utilization. This study demonstrates the benefit of exploring scenarios of data availability during modelling and will be especially valuable where the sampling effort differs greatly among variables. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Role of soil redox in growth and fertilizer nitrogen uptake by rice in Thailand paddy soils     

A. Jugsujinda  J. Prasittikhet  R.D. DeLaune  C.W. Lindau 《Soil Use and Management》1998,14(4):223-229

Abstract. In a laboratory study, ¹⁵N ammonium fertilizer uptake and rice growth was determined in a non-acid sulphate marine soil (Typic Tropaquept) and an acid sulphate soil (Sulfic Tropaquept). Acid sulphate sensitive (IR 26) and acid sulphate tolerant (IR 46) rice varieties were grown in soil suspensions incubated at four Eh levels (+500, +250, +50, and -150 mV) in microcosms for three weeks. The results showed that rice grown in non-acid sulphate marine soils gave slightly better dry matter weight of 1.8g/pot, greater ¹⁵N uptake of 12.8 mg N/pot, and higher total N uptake of 38.4 mg N/pot than under acid sulphate soil conditions indicating the non-acid marine soil is more favourable to rice culture. Growth as measured by weight of dry matter was significantly reduced from 2.1g/pot under oxidized condition (+500 mV) to 0.8g/pot under highly reduced condition (-150 mV). N uptake by rice was significantly reduced from 16.9 mg/pot at + 500 mV to 4.5 mg N/pot at -150 mV Total N uptake also decreased with decreasing Eh. Growth, ¹⁵N uptake and total N uptake by acid sulphate tolerant rice, IR 46 were significantly higher than the acid sulphate sensitive rice variety, IR 26. Under highly reduced soil conditions (-150 mV), growing rice in acid sulphate soil would require additions of lime, intermittent irrigation and/or mid season drainage in order to increase soil redox potential and remove toxic substances.  相似文献   

白三叶(Trifolium repens L)无性系植物分株间的生理整合作用     

胡宝忠  刘娣 《东北农业大学学报》1998,(1)

研究了白三叶无性系植物种群，在相互连接的分株之间生理上相互依存的程度。结果显示子代在生理上取决于母株资源的转移，这一依赖性随时间而下降。相互连接的分株，一部分被遮荫至１０％，而照光分株光合速率明显增加。光被限制期间，分株将重新整合，遮荫分株无性系中由其它分株提供同化物。在子代匍匐茎数目和长度上有一个权衡。当资源受限制时，产生极少较长的子代匍匐茎，结果提高了子代能够占据更有利条件的可能性。在分株之间，生理整合作用降低了子代建立所面临的危险，使同源分株在资源的可利用能力上整合到一个局部的异质环境，增加同源分株间的竞争能力，缓冲所面对的局部微生境的选择。  相似文献   

水稻施用硅钙肥试验总结   总被引：1，自引：0，他引：1  

龚宝林  王长青  朱德文  楮红宇 《北方水稻》2008,38(2):46-47

为了研究硅钙肥对水稻生育及产量的影响,采用寿益牌硅钙肥进行大区对比试验,供试的水稻品种为辽粳9号。试验结果表明:硅钙肥可促进水稻分蘖,茎秆高大粗壮,增强抗逆性,增产5.7%～7.3%,增收31.20、18.60元/667 m2。  相似文献   

3种生长调节物质对生菜不定芽直接再生的影响   总被引：3，自引：0，他引：3  

周音  张智奇 《吉林农业大学学报》1998,20(3):31-34

应用“３１１－Ｂ”回归最优设计研究ＡｇＮＯ３，ＡＢＡ，ＡＳＡ对生菜离体培养不定芽直接再生的影响。结果表明，ＡｇＮＯ３是良好的乙烯抑制剂，与ＡＢＡ配合使用可明显抑制愈伤产生，大大促进不定芽的直接再生；而ＡＳＡ未曾抑制愈伤产生，不是乙烯抑制剂。  相似文献   

兔胚胎的一些与分离胚胎干细胞有关的生物学特征   总被引：6，自引：1，他引：5  

赖良学  郑瑞珍 《中国兽医学报》1998,18(4):351-354

为获得具有发育全能性的胚胎干细胞（ＥＳ细胞），对３日龄、３．５日龄和４日龄家兔胚胎的形态结构和免疫组化特征进行了观察。家兔胚胎的外围，不仅有透明带，还包有一层很厚的胶膜。３日龄兔胚为桑椹胚；３．５日龄胚胎已出现囊胚腔，囊胚腔较小，扩增内细胞团（ＩＣＭ）占据囊腔的１／２～２／３；４日龄为囊胚，囊腔扩大，ＩＣＭ与囊胚腔的体积比值缩小。桑椹胚的卵裂球和３．５日龄、４日龄胚胎的ＩＣＭ，以碱性磷酸酶染色和胚胎阶段特异性细胞表面抗原－１（ＳＳＥＡ－１）免疫荧光标记均呈强阳性，说明它们是由未分化的细胞构成。因此，从保证全能性的角度考虑，３日龄、３．５日龄和４日龄的家兔胚胎，均可用于ＥＳ细胞的分离。  相似文献