Alteration of stimulus-specific guard cell calcium oscillations and stomatal closing in Arabidopsis det3 mutant     

Allen GJ  Chu SP  Schumacher K  Shimazaki CT  Vafeados D  Kemper A  Hawke SD  Tallman G  Tsien RY  Harper JF  Chory J  Schroeder JI 《Science (New York, N.Y.)》2000,289(5488):2338-2342

Cytosolic calcium oscillations control signaling in animal cells, whereas in plants their importance remains largely unknown. In wild-type Arabidopsis guard cells abscisic acid, oxidative stress, cold, and external calcium elicited cytosolic calcium oscillations of differing amplitudes and frequencies and induced stomatal closure. In guard cells of the V-ATPase mutant det3, external calcium and oxidative stress elicited prolonged calcium increases, which did not oscillate, and stomatal closure was abolished. Conversely, cold and abscisic acid elicited calcium oscillations in det3, and stomatal closure occurred normally. Moreover, in det3 guard cells, experimentally imposing external calcium-induced oscillations rescued stomatal closure. These data provide genetic evidence that stimulus-specific calcium oscillations are necessary for stomatal closure.  相似文献   

基于神经网络的电控发动机怠速不稳定的故障识别方法     

储江伟 《东北林业大学学报》2002,30(1):44-47

以电控发动机怠速不稳定这种十分常见的故障为研究对象。系统地介绍了应用神经网络进行故障原因识别的方法。详细地分析了不同网络结构的训练效率和以不同样本形式训练的网络对相同故障症兆的故障原因的识别能力。  相似文献   

Observation of polymer conformation hysteresis in extensional flow     

Schroeder CM  Babcock HP  Shaqfeh ES  Chu S 《Science (New York, N.Y.)》2003,301(5639):1515-1519

Highly extensible Escherichia coli DNA molecules in planar extensional flow were visualized in dilute solution by fluorescence microscopy. For a narrow range of flow strengths, the molecules were found in either a coiled or highly extended conformation, depending on the deformation history of the polymer. This conformation hysteresis persists for many polymer relaxation times and is due to conformation-dependent hydrodynamic forces. Polymer conformational free-energy landscapes were calculated from computer simulations and show two free-energy minima for flow strengths near the coil-stretch transition. Hysteresis cycles may directly influence bulk-solution stresses and the development of stress-strain relations for dilute polymer flows.  相似文献   

野柿A砧与几个甜柿品种嫁接早期亲和力观察     

高焕章  吴楚 《湖北农学院学报》2001,21(4):316-317,346

用3个不同甜柿（Diospyros kaki)品种与野柿（Diospyros kaki var.silvestris)A砧进行嫁接亲和力对比试验。结果表明：禅寺丸麻城甜柿与野柿A砧亲和性良好，定植二年生野柿A砧后嫁接建园，接后第1年始花，第2年结果，前川次郎与野柿A砧嫁接存在明显不亲和性，少量植株嫁接当年接口呈现大、小脚现象、次年枝条生长细弱，第3年植株萎缩。  相似文献   

Dispersed polaron simulations of electron transfer in photosynthetic reaction centers   总被引：4，自引：0，他引：4  

A Warshel  Z T Chu  W W Parson 《Science (New York, N.Y.)》1989,246(4926):112-116

A microscopic method for simulating quantum mechanical, nuclear tunneling effects in biological electron transfer reactions is presented and applied to several electron transfer steps in photosynthetic bacterial reaction centers. In this "dispersed polaron" method the fluctuations of the protein and the electron carriers are projected as effective normal modes onto an appropriate reaction coordinate and used to evaluate the quantum mechanical rate constant. The simulations, based on the crystallographic structure of the reaction center from Rhodopseudomonas viridis, focus on electron transfer from a bacteriopheophytin to a quinone and the subsequent back-reaction. The rates of both of these reactions are almost independent of temperature or even increase with decreasing temperature. The simulations reproduce this unusual temperature dependence in a qualitative way, without the use of adjustable parameters for the protein's Franck-Condon factors. The observed dependence of the back-reaction on the free energy of the reaction also is reproduced, including the special behavior in the "inverted region."  相似文献   

农业增长方式转变与农业投资问题研究   总被引：2，自引：0，他引：2  

褚保金  张兵 《南京农业大学学报》1997,20(2):100-106

论述了农业投资在推动农业增长方式的转变中的特殊地位和作用，以及农业投资规模，数量，结构和方向等对农业持续稳定增长的影响，并在此基础提出应确立有效的农业投资机制和正确的农业投资方向，对投资机制的确立和投资方向的调整提出了操作性较强的对策措施。  相似文献   

Spherical bilayer vesicles of fullerene-based surfactants in water: a laser light scattering study     

Zhou S  Burger C  Chu B  Sawamura M  Nagahama N  Toganoh M  Hackler UE  Isobe H  Nakamura E 《Science (New York, N.Y.)》2001,291(5510):1944-1947

The low solubility of fullerenes in aqueous solution limits their applications in biology. By appropriate substitution, the fullerenes can be transformed into stabilized anions that are water soluble and can form large aggregated structures. A laser light scattering study of the association behavior of the potassium salt of pentaphenyl fullerene (Ph5C60K) in water revealed that the hydrocarbon anions Ph5C60- associate into bilayers, forming stable spherical vesicles with an average hydrodynamic radius and a radius of gyration of about 17 nanometers at a very low critical aggregation concentration of less than 10(-7) moles per liter. The average aggregation number of associated particles in these large spherical vesicles is about 1.2 x 10(4).  相似文献   

云杉小黑天牛幼虫空间分布型的研究     

刘篆芳  王振经 《吉林林学院学报》1993,9(2):53-58

1988年在大兴安岭火烧迹地上,调查了云杉小黑天牛(Monochamus sutor L)幼虫的空间分布。采用扩散系数(C),Iwao的m—m回归分析如Taylor幂的法则等7种方法,测定云杉小黑天牛幼虫的空间分布型呈聚集分布,分布的基本成分是个体群。扩散蔓延规律为聚集型扩散。其聚集程度随火烧程度、有虫株率及虫口密度大于5～7个侵入孔/1000 cm~2时种群趋于随机或均匀分布。聚集原因分析表明,平均1000 cm~2树干面积上2.13头幼虫是该虫种群聚集机制发生变化的临界值。  相似文献   

肘形进水流道解析法探讨     

储训 《扬州大学学报(农业与生命科学版)》1986,(1)

本文采用数学分析的方法,建立了大型泵站肘形进水流道过水断面面积与内外壁边界几何参数之间的方程,并给出了方程的数值解法。与以往所采用的图解法相比,免除了繁琐的作图和校核修改过程,对应于一定的流速分布给出唯一的结果。  相似文献   

中国食蚜蝇亚科昆虫的区系分析（双翅目：食蚜蝇科）     

何继龙  储西平  孙兴全  陈文龙  叶文娟 《上海交通大学学报(农业科学版)》1996,(1)

本文对我国食蚜亚科昆虫的区系进行了分析。我国该亚科昆虫的区系具备以下特点：东洋区与古北区种类所占比重较大，两者分别占总种数的３０．１０％和２８．０６％，几乎相等；而特有种和广布种较为丰富；以食蚜蝇族的区系最具多样性。  相似文献