PERSISTENCE OF AMBROSIA TRIFIDA POPULATIONS IN OLD FIELDS AND RESPONSES TO SUCCESSIONAL CHANGES

A population of Ambrosia trifida L. (Asteraceae) in an annually ploughed field and an adjacent 15-year old population in an old field were compared to determine how plant responses, genotypic composition, and genetic variability change in populations over successional time. The two populations were originally part of a large contiguous population in an annually ploughed field. When individuals from the two populations were grown from seed in a common garden, they showed several significant differences in characteristics indicating different genotypic compositions in the two populations. Individuals from the old field population showed earlier emergence, lower leaf mortality, and greater numbers of leaves, biomass, seed production, and reproductive allocation relative to plants from the annually ploughed field. When sown in the field in a reciprocal transplant experiment, individuals from the two populations also differed in patterns of emergence, survivorship, yield, and fecundity. When grown together in a pairwise competition experiment, individuals from the old field population showed competitive superiority with respect to growth and seed production. This genetic differentiation between populations of different successional ages may be explained by natural selection imposed by the changing environment over successional time. However, the history and characteristics of these populations are such that founder effects may also be important in explaining the differences between them. A comparison of levels of variability in 14 different characters of individuals of the two populations showed no evidence that genetic variability in A. trifida populations declined over successional time.     

蟛蜞菊的生化他感作用及生化他感作用物的分离鉴定

蟛蜞菊是华南常见的园林绿化草本植物。植被调查表明其群落中杂草很少,形成蟛蜞菊纯群落。用琼脂培养基培养蟛蜞菊发现其分泌物对萝卜和黄瓜的萌发和幼草生长有生化他感作用。蟛蜞菊的组织抽提物对萝卜、稗草、马唐、窝苣和苜蓿５种植物幼苗生长都有抑制作用。用蟛蜞菊作覆盖物对马唐、大画眉草和空心莲子草幼苗生长有抑制作用。用真空液相色谱、快速柱色谱等赍蟛蜞菊地上部分离出２个纯化合物和１个较纯组分。纯化合物用质谱、红外     

MYCORRHIZAL AND CLIPPING EFFECTS ON ANDROPOGON GERARDII PHOTOSYNTHESIS

Mature Andropogon gerardii (Vitman) plants were placed in a 2 × 2 factorial treatment regime with clipping soil fumigation as main treatment effects. Plants were grown in a greenhouse using a Latin square design; pots were watered daily, and fertilized weekly with a low phosphorus nutrient solution. Photosynthesis and conductance were measured prior to and after a clipping which removed about 23% of the total leaf length of clipped plants. Fumigation reduced mycorrhizal colonization levels from 34.3 to 7.4%. Conductance was not affected by either treatment. Fumigated, clipped plants had significantly lower photosynthetic rates than their nonfumigated counterparts. However, there were no significant differences between fumigated and nonfumigated unclipped plants. The initial slope of the photosynthetic light response curve was significantly greater for the nonfumigated plants. Greater mycorrhizal development in nonfumigated plants appeared to be beneficial only when the host plants were under defoliation stress.     

ALLELOPATHIC EFFECTS OF DECAYING LITTER OF DOMINANT TREES AND THEIR ASSOCIATED SOIL IN A LOWLAND FOREST COMMUNITY

Phytotoxins released by the dominant species in a lowland forest showed highest accumulations in their respective stands. The accumulation of such phytotoxins corresponded with the amount of litter produced and its decaying rate. The release of phytotoxins and their activity depended on whether they were free or bound, and on their solubility. Therefore, the phytotoxins in soils were highly variable in amounts from one species stand to another species stand, during the same and different times of the year. The persistent accumulation of phytotoxins from all dominant tree species continues to influence the soil properties around the trees. Fourteen phytotoxins were isolated from the leaf litter and the soil. Seven persistent toxins were quantified in soils under different tree stands at various times of the year. The cycle of release of bound and free phenolics is discussed.     

东海原甲藻对羊栖菜合子生长及光合活性的化感作用研究

为评估东海原甲藻(Prorocentrum donghaiense)赤潮发生对羊栖菜(Sargassum fusiformis)幼苗产量的影响并探讨其化感机理,在实验室条件下分别利用浓度为1.00×10⁵cells/mL东海原甲藻活细胞悬浮液(LC)、细胞破碎液(RC)和无细胞滤液(FC)培养羊栖菜合子,并对其生长发育及光合活性进行测定。结果显示,LC、RC和FC均会抑制羊栖菜合子的生长、叶绿素a合成和光合活性,其中FC及LC对合子的抑制程度相似且均大于RC。JIP-test分析表明,FC及LC对合子的最大量子产率(φP_o)、性能指数(PI)及PSⅡ反应中心密度(RCs/ABS)的抑制作用显著大于RC。表明东海原甲藻主要通过向细胞外释放化感物质产生抑制作用,这些化感物质抑制了羊栖菜合子PSⅡ的电子传递,使PSⅡ部分光化学反应中心(RCs)失活,进而使大量激发能转化为热能被耗散掉。而RC中可能含有某些能够刺激羊栖菜合子生长的物质,从而在一定程度上抵消了化感物质的抑制作用。结果表明东海原甲藻对羊栖菜合子的抑制作用主要是由化感物质引起的,东海原甲藻赤潮可以抑制羊栖菜合子的发育和光合活性,减少羊栖菜种苗产量,并最终阻碍了羊栖菜产业的发展。     

东海原甲藻对羊栖菜合子生长及光合活性的化感作用研究

为评估东海原甲藻(Prorocentrum donghaiense)赤潮发生对羊栖菜(Sargassum fusiformis)幼苗产量的影响并探讨其化感机理,在实验室条件下分别利用浓度为1.00×10⁵cells/mL东海原甲藻活细胞悬浮液(LC)、细胞破碎液(RC)和无细胞滤液(FC)培养羊栖菜合子,并对其生长发育及光合活性进行测定。结果显示,LC、RC和FC均会抑制羊栖菜合子的生长、叶绿素a合成和光合活性,其中FC及LC对合子的抑制程度相似且均大于RC。JIP-test分析表明,FC及LC对合子的最大量子产率(φP_o)、性能指数(PI)及PSⅡ反应中心密度(RCs/ABS)的抑制作用显著大于RC。表明东海原甲藻主要通过向细胞外释放化感物质产生抑制作用,这些化感物质抑制了羊栖菜合子PSⅡ的电子传递,使PSⅡ部分光化学反应中心(RCs)失活,进而使大量激发能转化为热能被耗散掉。而RC中可能含有某些能够刺激羊栖菜合子生长的物质,从而在一定程度上抵消了化感物质的抑制作用。结果表明东海原甲藻对羊栖菜合子的抑制作用主要是由化感物质引起的,东海原甲藻赤潮可以抑制羊栖菜合子的发育和光合活性,减少羊栖菜种苗产量,并最终阻碍了羊栖菜产业的发展。     

老年大鼠血管α1肾上腺素受体及其亚型的改变

本工作用离体与整体实验方法,研究了老年(18月龄)与年轻(3月龄)大鼠血管中 α_1肾上腺素受体储备和 α_1(?)与 α_(1b)亚型比值的差别。在离体实验中用机械方法分离血管,用 Krebs 溶液灌流,在灌流液中加入 α_2和 β肾上腺素受体拮抗剂,然后用去甲肾上腺素(NE)激动 α_1受体。结果显示;老年大鼠主动脉、肾动脉和肠系膜动脉由去甲肾上腺素(NE)引起的最大收缩反应与年轻大鼠无显著差别,但浓度-效应曲线显著右移,功能性解离常数 K_A 值不变,而 K_A 与EC_(50)的比值减小。此外,在老年大鼠主动脉和肠系膜动脉血管,选择性 α_(1b)亚型拮抗剂 CEC对 NE 引起的缩血管效应的阻断作用显著减弱,硝苯吡啶(选择性阻断 α_(1a) 亚型的效应)对 NE 缩血管效应的阻断作用显著增强。整体实验显示老年大鼠硝苯吡啶的降血压作用比年轻大鼠增强,在用硝苯吡啶的基础上给予苯肾上腺素升血压作用减弱。上述结果提示:与年轻大鼠相比较,老年大鼠 α_(1-) 肾上腺素受体储备减少,α_(1a) 亚型相对 α_(1b)亚型的比率增高。     

ALLELOPATHIC AND HERBICIDAL EFFECTS OF EXTRACTS FROM TREE OF HEAVEN (AILANTHUS ALTISSIMA)

Mature trees of Ailanthus altissima produce one or more potent inhibitors of seed germination and seedling growth. Inhibitor activity is highest in bark, especially of roots, intermediate in leaflets, and low in wood. Crude extracts of Ailanthus root bark and leaflets corresponding to 34 and 119 mg water extractable material/L, respectively, caused 50% inhibition of cress radicle growth. Ailanthus seeds also contain one or more inhibitors. These are bound within the seed by the pericarp but diffuse into water agar when the pericarp is removed. The inhibitor(s) could readily be extracted from Ailanthus tissues with methanol, but not dichloromethane, indicating polar characteristics. Ailanthus leaflets had highest inhibitory activity during expansion in spring, whereas activity of trunk bark peaked just before emergence of leaves. This pattern suggests transport of allelochemicals from bark into new leaves. A comparison of seven plant species for sensitivity to the inhibitor(s) from Ailanthus root bark showed little selectivity, although velvetleaf was somewhat more resistant. The inhibitor(s) from Ailanthus root bark exhibited strong herbicidal effects when sprayed pre- and postemergence on plants in soil in the greenhouse. Postemergence effects were striking, with nearly complete mortality of all species, except velvetleaf, at even the lowest doses tested. The results suggest the allelochemical(s) from Ailanthus may have potential for development as natural-product herbicides.     

EFFECTS OF STATIC AND ELF MAGNETIC FIELDS ON FREE-RADICAL PROCESSES IN RAT LIVER AND KIDNEY

The aim of the study was to evaluate the activities of the antioxidant enzymes superoxide dysmutase (SOD, EC. 1.15.1.1), catalase (CAT, EC. 1.11.1.6), and glutathione peroxidase (GSH-Px, EC. 1.11.1.9) and the levels of malonic dialdehyde (MDA), a phospholipid peroxidation product, in the liver and kidneys of male and female rats exposed to static (0.49-T) and extremely low-frequency (50-Hz, 0.018-T) magnetic fields. Extremely low frequency magnetic fields increased all enzyme activities and MDA levels in both the liver and kidneys. In contrast, static magnetic field did not produce changes. The results of the study suggest that ELF magnetic fields affect free-radical processes in the liver and kidney.     

PHENODYNAMIC ANALYSES OF TWO FIRST-YEAR OLD FIELDS

Phenological spectra from two adjacent first-year old fields suggest that phenological events may be directed by the biotic influences of associated species as well as by climatic and edaphic conditions of the region. These two fields possessed similar macroclimatic conditions but had differing soil textures and crop histories. Phenological spectra were developed by observations made on all plant species occurring in fixed quadrats during the duration of this study, April 1, 1970, to October 20, 1970. The phenophases observed were initiation of vegetative growth, time of budding, occurrence of flowering, fruiting sequences, and time of seed set and dissemination. Production studies based on short-term harvest methods indicated the dominance of Erigeron canadensis in the abandoned soybean field, and Erigeron annus in the abandoned corn field.     

几种高等水生植物的克藻效应

研究了水花生、水浮莲、满江红、紫萍、浮萍和西洋菜对雷氏衣藻的相生相克关系,并和水葫芦的作用进行了比较。试验指出前五种水生植物对雷氏衣藻表现了克制作用,但它们的克藻效能不如水葫芦强。西洋菜没有克制作用,甚至稍有促进效应。从水花生、水浮莲、水葫芦的种植水中得到的分泌物粗提物,都显示了对雷氏衣藻的抑制效应,进一步证实了有相生相克关系的存在。试验结果说明高等水生植物对藻类的克制作用似有一定的普遍性,在水生生态系统的形成和演替过程中可能起着重要的作用。     

棉田蜘蛛群落及其多样性研究

本文对武汉地区棉田蜘蛛群落及其多样性进行了研究。结果如下:1)棉田蜘蛛种类较多,有30种;优势种为草间小黑蛛、三突花蛛、八斑鞘蛛和棕管巢蛛;2)控制打药区群落的多样性高于常规打药区;棉花生育后期群落的多样性高于生育前期。蜘蛛群落的多样性曲线由结网型蜘蛛亚群落的多样性曲线决定;3)棉花生育前期影响多样性的主要成分是种类丰富度,后期影响多样性的主要成分是均匀性。     

捕食者——食饵系统持久的充要条件及其分枝

本文研究了具无限时滞的捕食者-食系统的持续生存问题,得到了保证系统持续生存的充要条件,以此为基础,讨论了系统的持久性分枝问题．     

团头鲂MSTN基因cDNA结构、表达及过表达对胚胎发育的影响

研究通过cDNA末端快速扩增法(RACE)克隆得到团头鲂生长抑制素(MSTN)基因的cDNA全长并分析了MSTN基因在团头鲂胚胎、成鱼组织中表达以及MSTN基因在胚胎中过表达情况。结果表明团头鲂MSTN基因的cDNA全长为2187 bp, ORF(开放阅读框)大小为1128 bp, 编码376个氨基酸。组织逆转录PCR (RT-PCR)结果显示, MSTN基因在肌肉、脑和精巢组织中大量表达, 肝脏、脾脏和卵巢组织中的少量表达, 肠、腮、心、眼和肾组织中的微量表达。胚胎逆转录PCR (RT-PCR)结果显示, 在0—44 hpf胚胎发育阶段, MSTN基因表达量较低; 而在48—52 hpf胚胎发育阶段, MSTN基因表达量逐渐升高。整胚原位杂交(WISH)结果显示, 胚胎发育的16 hpf时期MSTN基因主要在脊索中表达, 胚胎发育的28 hpf和55 hpf时期MSTN基因在脑中表达。MSTN基因过表达结果显示, 胚胎在体节发生期出现前-后轴拉长, 背-腹轴变短; 脊索发生扭曲, 强烈抑制体节发育而导致不分化等现象。研究为后续团头鲂MSTN基因的功能研究及团头鲂分子育种提供相关参考依据。     

凤眼莲根系分泌物对塔玛亚历山大藻的化感作用(英文)

以塔玛亚历山大藻香港株(Alexandriumtamarense,HKstrain)为材料,研究了凤眼莲(Eichhorniacrassipes)根系分泌物及其丙酮、乙酸乙酯提取物对塔玛亚历山大藻的化感作用(Allelopathic effect)。凤眼莲根粉末的用量为0.1g/L、0.5g/L、1.0g/L、1.5g/L和2.0g/L;丙酮、乙酸乙酯提取物的用量为0.01g/L、0.03g/L、0.05g/L和0.07g/L。由于凤眼莲根系丙酮、乙酸乙酯提取物水溶性比较低,实验中,溶剂提取物置于盖玻片上。培养体系中溶剂提取物的实际浓度通过实验前后盖玻片的差值获得。实验结果表明,凤眼莲根粉末用量大于1.5g/L,对塔玛亚历山大藻抑制率100%,0.5g/L和1.0g/L4d后开始有促进生长的作用。凤眼莲根系丙酮、乙酸乙酯提取物的实际浓度达到0.038g/L、0.022g/L时,对塔玛亚历山大藻抑制超过50%。凤眼莲作为杀藻剂的材料有一定的应用前景。       

MNNG对细胞DNA合成及其分布的影响

本文用流式细胞光度术(FCM)等方法研究了MNNG,ENNG和DMS对HeLa细胞DNA含量分布的影响。经MNNG(6.8μmol/L)处理后,细胞分裂减少,DNA合成速率下降,S期细胞的比例随处理时间的延长而增加。DMS显示有类似的现象而ENNG的效应则较小。     

K物质在大鼠心脏内的分布及其对心血管活动的作用

本工作应用特异性K物质放射免疫分析法测定了大鼠心脏的K物质样免疫活性,心房和心室含量分别为19.9±3.5和4.1±0.8pmol/g组织。心脏内的K物质样免疫活性物质主要以单一分子形式存在。用免疫组织化学方法证明K物质免疫活性存在于心脏神经纤维内。大鼠心肌杂交细胞株(CP8401)细胞上含有K物质特异性结合部位,KD为1.61×10~(-10)mol/L,Bmax为8.08×10~(-12)mol/L。用心肌杂交细胞和离体心脏进行体外实验,证明K物质可释放ANF,这种释放可为速激肽受体拮抗剂[D-Pro~2,D-Trp~(7,9)]-SP部份抑制。给麻醉大鼠静脉注射K物质可引起血压降低、心率加快、左心室内压和收缩速度下降。这一作用亦可被[D-Pro~2,D-Trp~(7,9)]-SP所部份抑制。应用大鼠离体灌流心脏模型,发现K物质可升高心脏灌流压、左心室收缩期峰压、左心室内压最大上升速率和加快心率、具有正性变时和变力性作用。 本工作提示,K物质存在于心脏神经纤维内,在心肌细胞上具有K物质的特异性结合位点。K物质可促进心肌细胞释放心钠素,并可调节心脏的功能。