阔叶丰花草对荔枝园杂草群落特征及物种多样性的影响

【目的】明确阔叶丰花草在荔枝园定植对杂草群落特征及物种多样性的影响,为阔叶丰花草在果园应用提供参考依据。【方法】通过调查广东茂名高州荔枝国家现代农业产业园的荔枝园中90个有、无阔叶丰花草样方中杂草群落组成、群落高度以及物种多样性,探究阔叶丰花草定植对荔枝园杂草群落结构及物种多样性的影响。【结果】阔叶丰花草在荔枝园定植后,杂草种类减少,由对照样方的42种减少到试验样方的30种;杂草群落结构显著改变,牛筋草、白花鬼针草等恶性杂草重要值降低,薇甘菊、香附子、火炭母等杂草消失;阔叶丰花草的重要值与杂草群落高度和物种多样性指数为显著性负相关(P0.001),且均呈显著三项式回归关系。阔叶花草在荔枝园定植后可建立结构较为单一,且低矮的杂草群落。【结论】阔叶丰花草有望成为荔枝园生草的有益草种。     

不同稻作方式对稻田杂草群落的影响

运用半试验与调查相结合的方法,以贵州省从江县传统农业区的糯稻和杂交稻为例,研究了在水稻单作（R）、稻-鱼（R-F）和稻-鱼-鸭（R-F-D）3种不同稻作方式下稻田杂草群落的特征.结果表明：糯稻在3种稻作方式下的抑制杂草能力均优于杂交稻;R-F-D显著降低了田间杂草的发生密度,对鸭舌草、节节菜等的抑制效果达到100%,总体抑制杂草效果显著优于其他稻作方式,杂草的物种丰富度及Shannon多样性指数显著降低,Pielou均匀度指数提高,表明群落物种组成发生了很大的改变,降低了原来优势杂草的发生, 是一种较好的可达到抑制杂草效果的稻作方式.     

植物功能群去除对高寒草甸群落结构、多样性及生产力的影响

群落中物种的丧失在干扰下普遍存在,但对生态系统过程和功能的影响仍存在较大不确定性。选取青藏高原东缘典型高寒草甸为对象,开展优势植物功能群的梯度去除试验,以模拟长期过牧干扰下物种的损失。经过连续两个生长季的功能群去除,我们对群落的物种组成、结构、多样性和生物量等特征进行了分析,探讨了上述指标的响应过程和机制。研究结果表明：（1）功能群的去除降低了群落高度,增加了物种均匀度,并显著影响了禾草、杂草优势比以及功能群多样性和优势度;（2）同时,去除操作显著减小了凋落物量与禾草生物量,并显著影响了群落地上生物量;（3）进一步分析还发现,禾草、莎草和杂草功能群之间存在显著的竞争关系,群落生产力主要取决于禾草功能群并随物种均匀度的增大而显著减小。上述结果表明,禾草在高寒草甸群落中占据竞争优势地位,植物功能群的损失主要通过改变种间竞争关系、引起有机物质丢失影响群落过程和功能。     

黄竹侵入对群落生物量及植物多样性的影响

采用标准木法、回归分析法（乔木层）和样方法和相结合,分析了黄竹（endrocalamus membranaceus Munro)侵入对群落生物量的积累和物种多样性的影响,结果显示黄竹侵入严重影响生物量的积累,群落生物量随黄竹侵入量的增多而下降。随着黄竹侵入量的增加,群落内物种数量减少,物种多样性指数降低。     

人为干扰对金马河温江段护岸林物种多样性和土壤理化性质的影响

采用典型样地法,运用干扰理论和物种多样性分析方法,使用冗余分析（RDA）研究了11个环境因子与护岸林物种多样性的关系,探究不同强度人为干扰对金马河温江段护岸林物种多样性和土壤理化性质的影响。结果表明：（1）在264个不同层次样方中,记录植物122种,隶属65科102属,其中草本层物种数量最多,种类达89种,占总记录数73%,随人为干扰强度增加物种数量逐渐减少;（2）人为干扰对金马河护岸林群落物种多样性水平产生负面影响,随着干扰强度增加,群落各层次Shannon-Wiener多样性指数（H）和物种丰富度指数（D）逐渐降低,乔木层物种组成单一,造成群落环境功能和稳定性下降;（3）群落土壤pH值呈碱性,土壤有机质含量较高,不同干扰强度下各土壤理化性质具有显著差异（P<0.05）;（4）土壤含水量、速效钾、有机质含量是影响护岸林物种多样性的最主要因子。     

短期增温和降水减少对半干旱沙质草地群落特征的影响

【目的】为探究短期增温和降水减少对沙质草地植物群落物种多样性、功能性状及生产力的影响,进一步揭示沙质草地植物群落特征对气候变化的响应。【方法】以科尔沁沙质草地植物群落为研究对象,利用开顶式生长室(OTC)模拟增温,研究降水减少0%、20%、40%和60%与增温的交互作用对沙质草地群落组成、物种多样性和功能性状的影响及群落特征与环境因子关系。【结果】结果显示:（1）短期增温和降水减少使沙质草地植物群落组成和物种优势度发生变化,其中优势物种猪毛蒿和达乌里胡枝子在短期增温和降水减少处理下均明显降低,短期增温和降水减少均显著降低了植物群落盖度和地上生物量。（2）短期增温显著降低了Margalef丰富度指数、Simpson指数、Shannon多样性指数和Pielou均匀度指数,短期降水减少对沙质草地供试4种物种多样性指标均无显著影响。（3）短期增温显著提高了植物群落高度和叶干物质含量,显著降低叶厚度,短期降水减少显著提高了叶干物质含量和叶厚度,显著降低了植株高度和比叶面积。（4）短期增温是影响沙质草地物种多样性和功能性状的主要环境因素。【结论】综上可知,短期增温和降水减少改变了沙质草地群落特征,温度是影响沙质草地群落特征的主要环境因子。     

海南岛热带山地雨林群落物种多样性的空间格局分析

对海南岛四大林区的热带山地林群落物种多样性的分析表明,（1）林区间的乔木层和草木层物种多样性在从东到西（即吊罗山－五指山－坝王岭－尖峰岭）的群落中依次减少,灌木层和层间植物则增加,层间植物和乔木层在物种多样性的空间波动比灌木层和草本层有较高的稳定性;（2）林区内群落乔,灌、草及层间植物各层的物种多样性在海拔梯度上表现出不同的变化趋势;（3）林区内群落各层的物种多样性在不同坡向上也表现出不同的特征。     

佛坪国家级自然保护区植物群落物种多样性特征

用物种多样性指数（Simpson指数和Shannon指数）、均匀度指数（Pielou均匀度）和物种丰富度,对佛坪国家级自然保护区主要高等植物群落物种多样性进行了测度。结果表明：森林群落的多样性程度高于灌丛和草甸,落叶阔叶林高于针叶林,栎林高于杨桦林。群落物种多样性有随海拔高度的升高而降低的趋势。物种多样性在森林群落垂直结构上的分布特点,表现为一般乔木层与灌木层接近但低于草本层。     

黄河三角洲自然保护区典型植物群落物种组成及多样性梯度变化

以黄河三角洲自然保护区典型湿地群落为研究对象,探讨其物种组成及物种多样性的梯度变化规律。结果表明,从芦苇－香蒲群落到翅碱蓬群落梯度上：（1）群落物种丰富度呈波动性变化,旱柳－芦苇－白茅群落的物种丰富度最高,其次是芦苇－柽柳－翅碱蓬群落、芦苇－香蒲群落、柽柳－翅碱蓬群落,翅碱蓬群落的物种丰富最低;（2）群落的α多样性的变化格局与丰富度的变化格局不太一致,其中Shannon-Winner多样性指数与Pelou均匀度指数表现为波动性的下降趋势,而Simpson优势度指数则表现为波动性的上升趋势;（3）群落的β多样性变化格局也不完全相同,其中相异性系数呈波动性降低趋势,Copy指数则表现为先升高再降低的变化趋势。黄河三角洲典型湿地植物群落组成和物种多样性的梯度变化主要与生境变化有关。     

喀斯特石漠生态系统不同自然演替阶段中苔藓植物多样性特征分析

以“空间代替时间”方法研究了贵州喀斯特石漠地区植被自然恢复演替过程中各演替阶段苔藓植物的群落特征及苔藓植物物种α和β多样性指数。研究结果表明：该区共有苔藓植物群落21种,并以美灰藓（Eurohypnum leptothallum）为优势物种。苔藓植物α多样性指数随演替阶段的发展,表现出先下降、再反弹（藤刺灌丛阶段）、最后再次降低的变化趋势。苔藓植物Pielou均匀度指数的大小表现为：苔藓群落阶段（0.9392）〉 乔灌丛阶段（0.8675）〉 藤刺灌丛阶段（0.8651）〉 草灌丛阶段（0.7677）〉 草丛阶段（0.7676）。β多样性指数（Sorenson多样性指数）分析表明,苔藓植物群落随着演替阶段的发展,相同种类的数目随之减少,群落间相似性系数也逐渐降低。虽然苔藓植物群落在草丛阶段和藤刺灌丛阶段的相似性高于草丛阶段和草灌丛阶段之间的相似性系数,但总的相似性系数却呈现下降趋势。该研究结果可为喀斯特石漠生态系统演替的研究提供依据。     

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.     

真菌类遗传学分析的知识结构教学

本文以认知结构理论为指导,讨论了真菌类遗传分析与高等动植物遗传分析的内在联系,认为利用这种内在联系进行教学可收到好的效果并说明了作者的具体教学过程。 Abstract:In the paper, the relationship between genetic analysis of Fungi and genetic analysis of high animal and plant was discussed.A good results were obtained when we adopted this method in the teaching.     

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.