动物的的变态

变态是动物学中一个较重要的专用名词,有关内容在中学课本也多处涉及到。现择要介绍一点动物变态的知识,供动物学教学参考。何谓动物的变态动物由于外在和内在的原因,个体形态发生变化,这叫变态。但动物学所讲的变态,是狭义地从发生学角度理解,即胚胎不直接转变为成体,而是在后期发育过程中,先形成形态、生理、生态方面特殊的幼体,行独立生活和生长,以后在某阶段发生急剧变化,转变为成体。青     

活的不可培养的细菌的研究进展

活的不可培养微生物(VBNC)即一些微生物明显地丧失了可培养的特性,但是保留了自身原有的代谢活力,并且在一定条件下,又可以回复到可培养的状态。从VBNC细菌的诱导条件、生物学特性和检测方法3个方面对VBNC细菌研究进展做一综述。     

高频率的波动对于种子的萌发和植物的发育的影响

本文主要是以理论和试验来说明音波对植物的生长发育和种子萌发所起的影响。在农业实践上音波所起的作用,据现在所知:有缩短植物成熟期,加速萌芽和增强植物的生长发育等。这一些非但具有理论和实践上的意义,同时在今後把物理科学应用到农业科学中开辟了极广阔的前程。     

真核细胞的基因的组织

一、真核细胞基因的基本结构 1.转录单位: 从已知的数十种基因的顺序,可得出一个具有功能的基因的共同规律,在基因5’端-25至-75区,有CCAAT和TATAAA区(后者又称ATA box或Hogness box),相当于促进子区(Promotor),为体外转录所必需。     

由吸附的缩氨酸诱导的细胞膜的形变

研究了由一系列相互平行的吸附在细胞膜上的缩氨酸引起的膜的弹性形变,以及膜对缩氨酸的包裹行为,得到膜的平衡方程,用它可以来处理大尺度的形变,弯曲能量、吸附能量和弹性形变的相互竞争导致膜对缩氨酸发生从不吸附到部分吸附乃至完全包裹的结构转变．在膜的形变很小的时候,可以得到系统能量的解析解。     

远古的人们是怎样认识自己的起源的

人是从那里来的? 回答这个问题,你也许会说这有什么困难——人是从古猿变来的;甚至你还会进一步说,在这个从猿到人的转变过程中,劳动起着决定性的作用。然而这个现在看来比较明了的道理,恰是经历了多么漫长的认识过程才达到的呵!现在让我们首先来谈谈,远古的人们是怎样认识自己的起源的。最初的原始人可能还想不到自己的起源在人类诞生的最早时期,“最初的、从动物界分离出来的人,在一切本质方面是和动物本身一样不自由的”(恩格斯:《反杜林论》),这些最初的原始人为艰苦     

敲除pckA基因的结核杆菌引起的免疫反应的研究

研究结核杆菌pckA基因编码的磷酸烯醇型丙酮酸羧激酶(PEPCK)诱导机体产生的保护性免疫反应。用敲除pckA基因的牛结核杆菌BCG和野生型BCG分别感染小鼠,取肝、肺、脾进行病理分析,并进行脾细胞培养,检测CD4 、CD4 /CD8 、细胞因子IFNI-γI、L-12和TNF等。用敲除pckA基因的BCG感染的小鼠比野生型BCG感染的小鼠体内产生的结核结节少且不典型,炎性程度低。野生型BCG感染的小鼠脾脏内的CD4 T细胞和CD4 /CD8 、细胞因子IFN-γ、IL-12、TNF均明显高于敲除pckA基因BCG感染的小鼠。pckA基因为结核杆菌生长所必需,其编码产物PEPCK能够刺激机体产生免疫反应,是一种很好的疫苗候选分子。     

分离的蚕豆细胞核的RNA聚合酶活力的研究

利用Triton X-100对叶绿体膜的作用,可快速地从蚕豆幼叶制备较纯净的细胞核,它具有较高的RNA聚合酶活力。比较了两种分离核的方法,证明利用匀浆法制备的核具有较高的活力。核活力与发育时期有关系,茎端和第1对幼叶的核活力显著高于第2和第3对叶片的核活力。此外,核活力明显地受反应液内锰离子的抑制。     

正红菇的化学成分的研究

采用ＧＣ、ＨＰＬＣ、ＧＣ／ＭＳ．凝胶过滤层析等方法对正红菇（Ｒｕｓｓｕｌａ ｖｉｎｏｓａ）的某些成分的分析结果表明：正红菇其色素由红紫色素和黄色素两个组分的组成,其中红紫色素对酸稳定,对碱及高温不稳定,而黄色素对它们则表现一定的稳定性。其多糖含量２．７４％,含有五种多糖组分。在脂肪酸组成上,主要是油酸和亚油酸,并有可能 存在ＥＰＡ和ＤＨＡ。全氨基酸分析表明含有十六种氨基酸,必需氨基酸占总氨基酸的５     

麦长管蚜唾液中几种酶的鉴定、活力测定与功能分析

用Parafilm膜夹营养液法,以两种食料介质饲喂麦长管蚜Macrosiphum avenae 3龄若蚜并收集其唾液,对唾液中的酶类进行了鉴定、活力测定和功能分析。结果表明,在20%蔗糖介质提取液中,鉴定有果胶酶、多酚氧化酶和纤维素酶; 在水介质提取液中鉴定有纤维素酶; 两种介质提取液中都未鉴定出过氧化物酶。酶活力测定结果表明, 在20%蔗糖介质提取液中, 每30头蚜虫分泌的果胶酶、多酚氧化酶和纤维素酶的酶活力分别为2.59×10^-3 U/g、7×10^-3 U/g和7.89×10^-3 U/g; 在水介质提取液中,纤维素酶活力为3.68×10^-3 U/g。行为反应试验结果表明,果胶酶处理麦苗的挥发物组分能引起麦长管蚜寄生性天敌燕麦蚜茧蜂Aphidius avenae和捕食性天敌七星瓢虫Coccinella septempunctata 的嗅觉偏好反应,因此,果胶酶在麦长管蚜取食诱导小麦植株的间接防御反应中具有重要作用。     

Characterization of major hydrolytic enzymes secreted by Pythium myriotylum, causative agent for soft rot disease

Pythium myriotylum, an oomycetous necrotroph is the causal agent of soft rot disease affecting several crops. Successful colonization by necrotrophs depends on their secretion of a diverse array of plant cell wall degrading enzymes (CWDEs). The induction dynamics of CWDEs secreted by P. myriotylum was analysed as little information is available for this pathogen. Activities of CWDEs that included pectinase, cellulase, xylanase and protease were detected using radial diffusion assay and differential staining. In Czapek Dox minimal medium supplemented with respective substrates as carbon source, the increase in CWDE activities was observed till 8 days of incubation after which a gradual decline in enzymatic activities was observed. With sucrose as sole carbon source, all the enzymes studied showed increase in activity with fungal growth while with cell wall material derived from ginger rhizome as sole carbon source, an initial spurt in cellulase, xylanase and pectinase activities was observed 3 days post incubation while protease activity increased from three days of incubation and reached maximum at 13 days of incubation. To further evaluate the role of CWDEs in pathogenicity, UV-induced mutants (pmN14uv1) were generated wherein significant reduction in cellulase, pectinase and protease activities were observed while that of xylanase remained unchanged compared to wild type isolate (RGCBN14). Bioassays indicated changes in infection potential of pmN14uv1 thereby suggesting the crucial role played by P. myriotylum CWDEs in initiating the rotting process. Hence appropriate strategies that target the production/activity of these secretory hydrolytic enzymes will help in reducing disease incidence/pathogen virulence.     

Chitinase and peroxidase activities in sunflower hypocotyls: Effects of BTH and inoculation with <Emphasis Type="Italic">Plasmopara halstedii</Emphasis>

Systemic acquired resistance (SAR) can be induced in plants by incompatible pathogens, pathogen derived extracts, or certain chemicals as benzothiadiazole (BTH). The aim of this work was to compare changes in peroxidase and chitinase activities, enzymes considered as PR-proteins, caused by BTH and the pathogen Plasmopara halstedii. Hypocotyls from susceptible and resistant BTH-treated sunflower seedlings showed increased peroxidase and chitinase activities. Inoculation with P. halstedii increased chitinase and peroxidase activities in inoculated hypocotyls from susceptible but not from resistant sunflower seedlings.     

Physiological and biochemical studies on Fusarium oxysporum f. sp. lycopersici race 2 for its biocontrol by nonpathogenic fungi

Abstract The self-degradation of the phytopathogenic fungus Fusarium oxysporum f. sp. lycopersici race 2 ( F. oxysporum l. 2), which reached an autolysis degree of 72% after 60 days of incubation in stationary culture, occurred principally during the first 14 days of incubation, when considerable β-(1,3)-glucanase, pectinase, xylanase and chitinase activities were detected in the culture fluids. The levels of β-(1,3)-glucanase, pectinase, cellulase, chitinase and xylanase activities increased in the culture fluids of this fungus, when the culture medium was supplemented with different inducers. The vegetable juice (V8) that contained tomato juice, was the best inducer for most of these activities. Chitosan, glucosamine oligomers and Mucor rouxii mycelium extract were found to have an inhibitory effect on F. oxysporum l. 2 growth. When incubating cell walls from young mycelia of F. oxysporum l. 2 with enzymic precipitates obtained from autolyzed cultures of Mucor rouxii, Aspergillus nidulans, Penicillin oxalicum and Penicillium purpurogenum , degradations of 45%, 22%, 21% and 12%, respectively, were detected.     

Evaluation of plant growth promoting and colonization ability of endophytic diazotrophs from deep water rice

A study of the diversity of endophytic bacteria present in seeds of a deepwater rice variety revealed the presence of seven types of BOX-PCR fingerprints. In order to evaluate the plant growth promoting potential the presence of nitrogenase, indole acetic acid production and mineral phosphate solubilization were estimated in the representative BOX-PCR types. The seven representatives of BOX-PCR types produced indole acetic acid, reduced acetylene and showed specific immunological cross-reaction with anti-dinitrogenase reductase antibody. Only four types showed mineral phosphate solubilizing ability. Comparison of cellulase and pectinase activities showed differences among different BOX-PCR types. PCR fingerprinting data showed that one strain isolated from the surface sterilized seeds as well as the aerial parts of the seedlings of rice variety showed low cellulase and pectinase but relatively high ARA. On the basis of 16S rDNA nucleotide sequence and BIOLOG system of bacterial identification, this strain was identified as Pantoea agglomerans. For studying the endophytic colonization this strain was genetically tagged with the reporter gene, gusA. Histochemical analysis of the seedling grown in hydroponics showed that the tagged strain colonized the root surface, root hairs, root cap, points of lateral root emergence, root cortex and the stelar region. Treatment of the roots with 2,4-D produced short thickened lateral roots which showed better colonization by P. agglomerans.     

Comparative physiological analysis in the tolerance to salinity and drought individual and combination in two cotton genotypes with contrasting salt tolerance

Soil salinity and drought are the two most common and frequently co‐occurring abiotic stresses limiting cotton growth and productivity. However, physiological mechanisms of tolerance to such condition remain elusive. Greenhouse pot experiments were performed to study genotypic differences in response to single drought (4% soil moisture; D) and salinity (200 mM NaCl; S) stress and combined stresses (D + S) using two cotton genotypes Zhongmian 23 (salt‐tolerant) and Zhongmian 41 (salt‐sensitive). Our results showed that drought and salinity stresses, alone or in combination, caused significant reduction in plant growth, chlorophyll content and photosynthesis in the two cotton genotypes, with the largest impact visible under combined stress. Interestingly, Zhongmian 23 was more tolerant than Zhongmian 41 under the three stresses and displayed higher plant dry weight, photosynthesis and antioxidant enzymes activities such as superoxide dismutase (SOD), peroxidase (POD) catalase (CAT) and ascorbate peroxidase (APX) activities compared to control, while those parameters were significantly decreased in salt‐stresses Zhongmian 41 compared to control. Moreover, Na⁺/K⁺‐ATPase activity was more enhanced in Zhongmian 23 than in Zhongmian 41 under salinity stress. However, under single drought stress and D + S stress no significant differences were observed between the two genotypes. No significant differences were detected in Ca²⁺/Mg²⁺‐ATPase activity in Zhongmian 41, while in Zhongmian 23 it was increased under salinity stress. Furthermore, Zhongmian 23 accumulated more soluble sugar, glycine‐betaine and K⁺, but less Na⁺ under the three stresses compared with Zhongmian 41. Obvious changes in leaf and root tips cell ultrastructure was observed in the two cotton genotypes. However, Zhongmian 23 was less affected than Zhongmian 41 especially under salinity stress. These results give a novel insight into the mechanisms of single and combined effects of drought and salinity stresses on cotton genotypes.     

Mutants ofXanthomonas campestris defective in secretion of extracellular enzymes

Summary Mutants ofXanthomonas campestris B 1459 were isolated that are defective in secretion of both cellulase and amylase. Both enzymes accumulated in the periplasmic space. The defects in secretion of cellulase or amylase were partly overcome by introducing into the mutants specific multiple copies of DNA cloned fromX. campestris, and presumed to code for cellulase or amylase enzymes. The mutant strains also showed reduced amounts of extracellular pectinase and protease activities, as if the mutants were generally defective for secretion of extracellular enzymes. The mutants showed reduced pathogenesis for turnip seedlings. The secretion-defective mutants may allow production of xanthan gum with reduced cellulose, pectin, protein and starch-degrading enzyme activities, thereby allowing more widespread mixing of microbially produced xanthan gum with these commercially important water-soluble polymers.     

Morphological and Molecular Characterization of Pomegranate Fruit Rot Pathogen, <Emphasis Type="Italic">Chaetomella raphigera</Emphasis>, and its Virulence Factors

A new fungal pathogen was isolated from rotten pomegranates collected from the orchards of different parts of Maharashtra. The pathogen was morphologically identified as Chaetomella raphigera followed by sequencing of ITS and D1/D2 hypervariable region of LSU (28S) of rRNA gene. The pathogen produced pectinase, cellulase, xylanase and protease in liquid medium at a concentration of 71, 13.8, 54.3 and 7 U/ml respectively. Enzyme activity was also determined during pathogenesis in the tissues artificially infected by C. raphigera. Xylanase activity was maximum (25.1 U/g) followed by pectinase (19.2 U/g) and cellulase (1.5 U/g), whereas, protease activity was unnoticed. There was significant correlation (P < 0.05) between disease rating scale and pectinase, xylanase and cellulase activity in infected tissues. This indicates the simultaneous production of hydrolytic enzymes that aids in necrosis of fruit tissues. The elevated levels of these enzymes in infected tissues as compared with control suggest their possible role in pathogenesis. Thus, pectinase, cellulase and xylanase produced by C. raphigera acts as major virulence factors in the development of fruit rot in pomegranates. This is a first report of fungal fruit rot caused by C. raphigera in pomegranate.     

Salicylic acid and ethylene pathways are differentially activated in melon cotyledons by active or heat-denatured cellulase from Trichoderma longibrachiatum

Infiltration of cellulase (EC 3.2.1.4) from Trichoderma longibrachiatum into melon (Cucumis melo) cotyledons induced several key defense mechanisms and hypersensitive reaction-like symptoms. An oxidative burst was observed 3 hours after treatment and was followed by activation of ethylene and salicylic acid (SA) signaling pathways leading to marked induction of peroxidase and chitinase activities. The treatment of cotyledons by heat-denatured cellulase also led to some induction of peroxidase and chitinase activities, but the oxidative burst and SA production were not observed. Co-infiltration of aminoethoxyvinil-glycine (an ethylene inhibitor) with the active cellulase did not affect the high increase of peroxidase and chitinase activities. In contrast, co-infiltration of aminoethoxyvinil-glycine with the denatured enzyme blocked peroxidase and chitinase activities. Our data suggest that the SA pathway (induced by the cellulase activity) and ethylene pathway (induced by heat-denatured and active protein) together coordinate the activation of defense mechanisms. We found a partial interaction between both signaling pathways since SA caused an inhibition of the ethylene production and a decrease in peroxidase activity when co-infiltrated with denatured cellulase. Treatments with active or denatured cellulase caused a reduction in powdery mildew (Sphaerotheca fuliginea) disease.     

玉米幼苗萎蔫过程中某些理化性质变化的研究

玉米幼苗在暂时性萎蔫期间失水速率相对较慢,可溶性糖,脯氨酸等渗透调度物质的积累较多,ＳＯＤ活性增加,而在永久性萎缩期间失水速率较快,渗透调节物质减少,ＳＯＤ活性下降,在玉米幼苗萎蔫的全过程中,叶绿素,蛋白质含量及ＣＡＴ,ＰＯＤ活性等迅速下降,质膜透性增大,膜脂过氧化加剧。