一氧化氮处理对香蕉多聚半乳糖醛酸酶及MaPGs基因表达的影响

为了解多聚半乳糖醛酸酶（PG）在香蕉采后软化中的分子调控机制,采用40 μL/L NO熏蒸处理绿熟期的‘巴西’香蕉果实3 h后,在20℃和相对湿度为85%的条件下贮藏,研究NO对香蕉果实乙烯释放量、硬度、PG活性及MaPGs基因表达的影响。结果表明：NO处理降低了果实乙烯释放量,延缓了果实硬度的下降,抑制了PG的活性;降低了MaPG2、MaPG3和MaPG4基因的表达,延缓了香蕉果实的软化。     

低温下芒果果皮的冷害及过氧化物酶和纤维素酶活性

热带水果—芒果对贮存低温的反应十分敏感,其冷害特征是果皮褐变、果皮上有凹痕、果实软化不均匀,因此,对冷藏期间果实的过氧化物酶和纤维素酶活性的研究是有意义的。 选择均匀的绿熟芒果(Keitt)果实,在5℃和20℃下各贮存50个。在5℃贮存的果实,21天后转移至20℃让其转熟。定期(20℃贮存0、4、11天,5℃贮存0、7、14、21、22、27天后再转移至20℃)随机取样,每组5个果实,去皮。果皮用丙酮在     

果实成熟的味感变化及其生理生化基础

果实成熟是指果实在生长末期经过一系列生理生化变化而达到食用品质的最佳状态的过程。在此过程中 ,果皮的颜色、果实的味感和硬度等均产生变化。其中 ,味感变化尤为明显和重要。1　甜度增加许多果实未成熟时 ,往往没有甜味或甜味较淡。随着成熟过程的进展 ,甜度才逐渐增加。果实中所含的糖类主要包括贮藏性糖和结构性糖两大类。贮藏性糖主要是可溶性糖 (如蔗糖、葡萄糖和果糖 )和淀粉。结构性糖主要是构成果实细胞壁的果胶类物质。在果实成熟中 ,淀粉可转化为可溶性糖 ,从而使甜度增加。例如香蕉 ,未成熟时淀粉含量占果实重量的 2 0 %～ 2 …     

猕猴桃果实采后成熟过程中糖代谢及其调节

20℃下采后猕猴桃果实中淀粉酶活性快速上升于果实软化启动阶段,随着果实进入快速软化阶段,淀粉迅速水解,葡萄糖和果糖快速积累,SPS活性增加,酸性转化酶活性下降,蔗糖积累;至果实软化后期,SPS活性降低,蔗糖含量下降.AsA和低温可抑制淀粉酶活性、己糖积累、SPS活性上升和酸性转化酶活性下降,延缓蔗糖积累,相反,乙烯则可促进淀粉酶活性,加速淀粉降解和己糖积累进而直接或间接增加SPS活性,促使蔗糖积累.采后猕猴桃果实的SPS活性变化中有己糖激活效应和蔗糖反馈抑制效应.AsA、低温和乙烯等对糖代谢的调节主要是通过对SPS活性的影响而实现的.     

香蕉果实成熟软化时果皮和果肉中α-L-阿拉伯呋喃糖苷酶活性的变化

阿拉伯糖是果实软化过程中变化最明显的细胞壁糖残基之一,α-L-阿拉伯呋喃糖苷酶是导致细胞壁多糖中阿拉伯糖残基降解的主要糖苷酶。为阐明该酶在香蕉果实成熟软化中的作用,实验对香蕉贮藏过程中果皮和果肉中该酶活性以及果实硬度、呼吸强度和乙烯释放量的变化进行了研究。结果表明:α-L-阿拉伯呋喃糖苷酶在果实初期的变化很小,到果实硬度开始急剧下降时达到最大,增加量达10倍以上,且果肉中的酶活性大于果皮中;乙烯吸收剂处理延缓了香蕉果实呼吸和乙烯高峰的出现时间,降低了果实硬度、果皮和果肉中α-L-阿拉伯呋喃糖苷酶活性变化的速度和幅度。以上结果表明α-L-阿拉伯呋喃糖苷酶起诱导香蕉果实成熟的作用,在果实的软化中起着十分重要的作用,且其活性受乙烯的调节。     

海南秋芒采后贮藏期间的生理变化（简报）

海南秋芒采后贮于室温条件下（２８～３５℃）第６ｄ呼吸速率达到高峰,果实变黄,果皮中果胶甲酯酶（ＰＥ）和多聚半乳糖醛酸酶（ＰＧ）活性分别有采后第７和第１１ｄ最高,果肉组织中纤维素酶活性在采后９ｄ最高,其ＰＥ和ＰＧ活性与果皮中的变化规律相似,均与果实的后熟进程关系密切;多酚氧化酶（ＰＰＯ）和过氧化物酶（ＰＯＤ）活性变化与果实软化没有明显相关性。     

钙对不同成熟期番茄果实的PG活性及其合成的影响

本文研究了钙处理不同成熟期番茄果实对果壁组织中钙含量与转化、多聚半乳糖醛酸酶(PG)活性与 PG 合成的影响。结果表明,钙处理绿熟期的番茄果实可使总钙和可溶性钙含量明显增加,并较多转化为结合钙;后期处理,进入和转化的钙都减少。同样,钙处理愈早,对果实 PG 活性的抑制愈强,绿熟期处理可完全抑制 PG 活性。凝胶电泳结合钌红染色,证明绿熟期果实无 PG,PG 是在果实成熟过程中新合成的。钙处理愈早,对 PG 合成的抑制愈强,绿熟期钙处理可完全抑制 PG 合成。     

采后芒果的后熟软化与贮藏淀粉变化之间的关系

研究了芒果后熟软化与贮藏淀粉变化之间的关系。结果表明,采后芒果淀粉的水解和消失,是使中果皮细胞壁失去支撑致使果实软化的重要原因之一。杀菌剂普克唑对芒果后熟软化和贮藏淀粉形态学的变化稍有延迟作用;2,4－D处理可以明显推迟后熟软化,减慢果实硬度的降低和淀粉的水解,而乙烯利处理则能催熟芒果,显著加速硬度丧失和淀粉的水解及其含量的减少。     

猕猴桃果实成熟进程中木葡聚糖内糖基转移酶mRNA水平的变化

以中华猕猴桃（ActinidiachinensisPlanch．）果实为试材,木葡聚糖内糖基转移酶（XET）cDNA为探针,研究果实成熟进程中XETmRNA的变化规律,探讨XET在果实后熟软化过程的作用。结果表明,20℃下外源乙烯处理可促进XETmRNA的积累,且这种效应因乙烯处理时间的加长而加强,进而加速了果实软化;0℃处理可抑制XETmRNA的增加,延缓果实软化,但当果实转入20℃后熟时,果实硬度迅速下降,而XETmRNA水平变化不明显。认为XET可能只是一种诱导酶,由它引起的细胞壁解聚并非是猕猴桃果实后熟软化的关键因子。     

‘爱文’芒果成熟阶段的蔗糖代谢

芒果（Mangifera indica L．）品种‘爱文’取自本所芒果园。于盛花期（3月8日）选择生长发育良好,长势、花期一致的树,从绿熟期（6月12日）开始取样,每4d取样1次,并于6月28日（商熟期）采摘的果实放在室温（35℃）下进行后熟试验。每次取大小一致的果实,以蒸馏水清洗后,保存于-30℃低温冰箱中待测。可溶性总糖和有机酸测定参照高俊凤（2000）书中的方法,     

六种藓类植物茎的比较解剖学研究

通过对6种藓类植物,即褶叶青藓(Brachythecium salebrosum(Web.et Mohr.)B.S.G.)、湿地匐灯藓(Plagiomnium acutum(Lindb.)Kop.)、侧枝匐灯藓(Plagiomnium maximoviczii(Lindb.)Kop.)、大凤尾藓(Fissidensnobilis Griff.)、大羽藓(Thuidium cymbifolium(Doz.et Molk.)B.S.G.)和大灰藓(Hypnum plumaeforme Wils.)嫩茎和老茎的石蜡切片和显微观察发现,同一藓类植株的嫩茎和老茎,茎结构稳定,不同种藓类植物茎横切面具有不同特征.植物体茎横切面形状、表层细胞的层数、细胞大小和细胞壁厚薄、皮层细胞大小和形状、中轴的有无以及比例等特征可以作为藓类植物的分科分类依据之一.     

Photoregulation of seed germination of wild-type and of an aurea-mutant of tomato

Seed germination of an aurea mutant of tomato ( Lycopersicon esculentum Mill.) is promoted by continuous irradiation with red, far-red or long-wavelength far-red (758 nm) light as well as by cyclic irradiations (5 min red or 5 min far-red/25 min darkness). Far-red light applied immediately after each red does not change the germination behaviour. Seed germination of the isogenic wild-type, cv. UC-105, is promoted by continuous and cyclic red light while it is inhibited by continuous and cyclic far-red light and by continious 758 nm irradiation. Far-red irradiation reverses almost completely the promoting effect of red light. The promoting effect (in the aurea mutant) and the inhibitory effect (in the wild-type) of continuous far-red light do not show photon fluence rate dependency above 20 nmol m⁻² s⁻¹. It is concluded that phytochrome controls tomato seed germination throgh low energy responses in both the wild type and the au mutant. The promoting effect of continuous and cyclic far-red light in the au mutant can be attributed to a greater sensitivity to P_fr.     

Cause of Senescence of Nine Sorts of Flowers

The levels of endogenous phytohormones and respiratory rate in nine sorts of flowers such as Cymbidium faberi Rolfe, Nopalxochia ackermannii Kunth and others were investigated both at full bloom and senescence and meanwhile the effect of exogenous phytohormones on prolonging the blossoms and promoting ethylene production were tested. There is a high content of endogenous ethylene in all the long-lived flowere, about 3–16 folds higer than the short-lived ones. There is a high level of ABA at full blooming flowers of short-lived flowers, in which there is no or only some cytokinins in it, but the ratio of CTK (6BA+zeatin)/ABA is smaller(l.7). The endogenous ABA reached a much higher level at senescence in all nine sorts of flowers, so it is reasonable to consider that it is ABA which plays an important role of regulation in controlling flower's senescence. There is a much higher level of GA3 and zeatin in the long-lived flowers which is not demonstrated in the shortlived ones. The respiratory rate is one of the factors controtling the longevity of flowers, but it does not play a decided role. Application of 6BA and zeatin prolongs distinctly orchid’s longevity, however exogenous IAA through the promotive action on ethylene production, evidently extends the longevity of the flowers of the Nopalxochia ackermannii Kunth.     

Interconnection of parameters of regulation system of lipid peroxidation and of morphophysiological parameters of mouse liver

A complex analysis of seasonal fluctuations of the mean group parameters of the system of regulation of lipid peroxidation has been performed in liver of Balb/c mice. Association of lipid characteristics and morphophysiological parameters is studied in the Balb/c mouse liver. An inter-connection is revealed between the liver index and the amount of lysoforms of phospholipids, the scale and character of the interconnection differing essentially depending on proportion of phos-phatidylcholine in mouse liver phospholipids.     

龙胆科药用植物化学成分的研究现状

龙胆科植物在我国的分布范围很广,且多数为药用植物,其多数种属的药用植物,至今其化学成分尚未被系统研究。综述了目前龙胆科药用植物的化学成分的研究现状及一般提取方法,对近年来发现的环烯醚萜及裂环烯醚萜类化合物进行了总结,为本科药用植物的更深入研究提供了参考。     

Physiological characteristics of various species of strains of carboxydobacteria

Seven strains of aerobic carbon monoxide-oxidizing bacteria (carboxydebacteria) when growing on CO as sole source of carbon and energy had doubling times which ranged from 12–42 h. The activity profiles obtained after discontinuous sucrose density gradient centrifugation indicated that the CO-oxidizing enzymes are soluble and the hydrogenases are membrane-bound in all strains examined. The CO-oxidizing enzymes of Pseudomonas carboxydohydrogena, Pseudomonas carboxydoflava, Comamonas compransoris, and the so far unidentified strains OM2, OM3, and OM4 had a molecular weight of 230,000; that of Achromobacter carboxydus amounted to 170,000. The molecular weights of the CO-oxidizing and H₂-oxidizing enzymes turned out to be identical. The cell sonicates were shown to catalyze the oxidation of both CO and H₂ with methylene blue, thionine, phenazine methosulfate, toluylene blue, dichlorophenolindophenol, cytochrome c or ferricyanide as electron acceptors. Methyl viologen, benzyl viologen, FAD⁺, FMN⁺, and NAD(P)⁺ were not reduced. The spectrum of electron acceptors was identical for all strains tested. Neither free formate, hydrogen nor oxygen gas were involved in the CO-oxidation reaction. Methylene blue was reduced by CO at a 1:1 molar ratio. The results indicate that CO-oxidation by carboxydobacteria is catalyzed by identical or similar enzymes and that the reaction obeys the equation CO+H₂OCO₂+2H⁺+2e^- as previously shown for Pseudomonas carboxydovorans.Dedicated to Otto Kandler remembering almost three decades of enjoyable cooperation     

Modulation of allostery of pyruvate kinase by shifting of an ensemble of microstates

Since the introduction of the concepts of allostery about four decades ago, much advancement has been made in elucidating the structure-function correlation in allostery. However, there are still a number of issues that remain unresolved. In this review we used mammalian pyruvate kinase (PK) as a model system to understand the role of protein dynamics in modulating cooperativity. PK has a triosephosphate isomerase (TIM)(α/β)₈ barrel structural motif. PK is an ideal system to address basic questions regarding regulatory mechanisms about this common (α/β)₈ structural motif. The simplest model accounting for all of the solution thermodynamic and kinetic data on ligand-enzyme interactions involves two conformational states, inactive E^T and active E^R. These conformational states are represented by domain movements. Further studies provide the first evidence for a differential effect of ligand binding on the dynamics of the structural elements, not major secondary structural changes. These data are consistent with our model that allosteric regulation of PK is the consequence of perturbation of the distribution of an ensemble of states in which the inactive E^T and active E^R represent the two extreme end states. Sequence differences and ligands can modulate the distribution of states leading to alterations of functions. The future work includes: defining the network of functionally connected residues; elucidating the chemical principles governing the sequence differences which affect functions; and probing the nature of mutations on the stability of the secondary structural elements, which in turn modulate allostery.     

（鱼句）亚科花（鱼骨）型鱼类骨骼系统的比较

对我国花型Hemibarbuspattern鱼类作了骨骼系统比较,结果表明,此类型鱼类脑颅较长,副蝶骨平直或稍弯曲,眶蝶骨腹纵嵴发达(铜鱼Coreius septentrionalis例外),下颞窝和咽突中等大,基枕骨后突发达;脑颅中的上筛骨的后突、侧筛骨的外筛突,蝶耳骨的外突、上耳骨的后突、围眶骨和后颞窝等均有明显的差异;咽颅中的舌颌骨、尾舌骨、鳃盖骨和下咽齿的列数等又有显著的区别;附肢骨骼中的腰带骨、脊椎骨中的复合神经骨和第4椎骨腹侧的悬器等也有不同之处。据此,这些差异和区别可作为属间或种间的分类依据。