Population structure and dynamics of Pinus massoniana Lamb. on mount Jinyun,Sichuan, China

Masson Pine (Pinus massoniana Lamb.) is a pioneer in forest succession in the subtropics of East Asia. However, the species persits, though with decreasing abundance, throughout the various successional phases. Agestructure, spatial pattern, density, population biomass, and their dynamics are described for a population in Sichuan, China, on the basis of a census of all individuals in the population while substituting space with time. In the course of succession, the population density increases and its rate of growth decreases until self-thinning starts; during the phase of self-thinning density decrease and continues to decrease even afterwards, but the rate of growth increase markedly after self-thinning has stopped. The development of population biomass (Bp) during the early succession from shrub-grassland to the early stages of mixed pine and broad-leaved forest can be described by a logistic equation. Later, Bp decrease rapidly. These changes are governed partly by inherent biological features of P. massoniana and partly by the invasion, establishment and development of shade-tolerant evergreen broad-leaved trees. Both self- and alien-thinning occur. Soil conditions affect the rates of these processes.     

竹红菌甲素敏化嘌呤和嘧啶碱的光氧化作用及其影响因素

本工作利用光吸收和高效液相色谱(HPLC)技术研究了甲素对DNA分子中四种碱基A、G、C和T光氧化的敏化作用,发现在反应体系的pH为9.0、甲素浓度为3×10~(-5)mol/L、光照40分钟时,G和T紫外吸收明显降低;HPLC分析发现甲素敏化的G光氧化体系比对照体系多出现一组分峰(滞留时间0.927分钟),该峰用475nm波长检测比260nm波长检测灵敏。根据反应机制推测是G环破裂产物。在反应条件固定时,甲素敏化G的光氧化作用受pH、光照时间及甲素浓度影响极大。单线态氧淬灭剂——叠氮钠浓度在40—110mmol/L可部分抑制甲素敏化G的光氧化作用,>110mmol/L时反应完全被阻断,提示甲素对G光氧化的敏化作用主要通过单线态氧(~1O_2)即Ⅱ型机制起作用。本文还讨论了G光氧化的可能途径。     

不同类群酵母胞壁甘露聚糖核磁共振氢谱的比较研究

运用核磁共振氢谱(PMR谱)~(**)对各类酵母的细胞壁甘露聚糖进行比较研究,在我国尚无报道,其中某些酵母也尚无文献记载。本文结果表明:1.同菌株的胞壁甘露聚糖PMR谱型的重复性很好。2.同种不同株的酿酒酵母(Saccharomyces cerevisiae)的多糖谱型也相同。3.所测的二端芽殖酵母中完全型与不完全型菌株的谱型很相似,如柠檬形克勒克酵母(Kloeckera apiculata)与葡萄有孢汉逊酵母(Hanseniaspora uvarum。4.某些分类系统上来源较杂的子囊菌酵母如单宁管囊酵母(Packysolen tanophilus)、萤光威克酵母(Wickerhamiaflurescens)与高糖固囊酵母(Citeromyces matritensis)则体现了各不相同的谱型。5.二株分自西双版纳的极为相近的类酵母(Saccharomycodes sp.)其多糖的(PMR)谱型与多糖的组分都彼此相同,有助于对它们的适当归类。这一切证明酵母胞壁多糖PMR谱型相似程度的比较是分类上较有意义的性状,有助于探讨亲缘关系,核实完全型与不完全型,也有助于对疑难菌株的分析     

大布苏的细石器

本文记述了发现于吉林省西部大布苏泡子东岸二级阶地前缘原生黄土状地层中的486件石制品,其中包括8件石器及100多件细石叶。大布苏地点的细石器材料,类型简单,成型的石器少,分布范围有限,可能是一个临时石器加工点。其时代初步定为旧石器时代末期。     

Site-directed mutagenesis of an apolipoprotein E mutant, apo E5(Glu3----Lys) and its binding to low density lipoprotein receptors.

Apo E5(Glu3----Lys) is a naturally occurring apolipoprotein E (apo E) mutant found in patients with hyperlipoproteinemia and atherosclerosis. It has been shown to have a high affinity for low density lipoprotein (LDL) receptors. In this study, mutant apo E5 was produced by Chinese hamster ovary cells by means of an in vitro site-directed mutagenesis technique, and its LDL receptor binding activity was assessed. The apo E5 obtained from gene expression bound more readily to the LDL receptor than did plasma apo E3. The concentrations required for 50% competitive binding of 125I-labeled LDL to the LDL receptors were 58.9 ng/ml for plasma apo E3 and 25.7 ng/ml for the expressed apo E5. The expressed apo E5 displayed 229% normal binding. This result is highly consistent with that obtained with plasma apo E5, which showed 217% normal binding. Although the experimental apo E isoproteins contained more sialic acid than plasma apo E, the extent of sialylation had no effect on the receptor binding of apo E.     

Increased shikonin production inLithospermum erythrorhizon suspension cultures within situ extraction and fungal cell treatment (elicitor)

Summary The effect ofin situ extraction and elicitor treatment on shikonin production was studied with the suspension cultures ofLithospermum erythrorhizon. Shikonin concentration of 60 mg/L was achieved by the use of both techniques which was 24 times higher than that of control culture, and 65 times higher in terms of shikonin productivity. The host-pathogen effect of elicitor treatment andin situ extraction for product removal were effective for shikonin production.     

中国连香树科的系统研究——Ⅰ.叶的宏观结构及叶柄维管束变化

本文研究了连香树科(Cercidiphyllaceae)叶的宏观结构,首次报道连香树齿腺体显微结构及晶体类型,并对叶柄维管束的变化作了进一步研究。通过与近缘科的比较,我们认为连香树科的系统演化处于孤立地位,和金缕梅科有较近的亲缘关系,与木兰科较为疏远。     

灯光诱虫在森林—鱼塘复合生态系统中的作用

昆虫是森林生态系统中的重要组成部分。由于森林中枯枝落叶较多,生境复杂,为昆虫提供了良好的繁殖和栖息场所;因而在森林中昆虫的种类多,数量大。大多数昆虫都以森林     

葡萄胚珠,胚乳及胚的发育

本文研究了“早玫瑰”和“新玫瑰”葡萄胚珠、胚乳和胚的发育。结果表明:花后3天胚珠即开始迅速生长,其生长的最终大小依品种成熟期的不同而各异。胚乳游离核在花后33天成为细胞状态。受精后16—21天,合子才开始第一次分裂。当胚乳充满珠心组织时,胚开始迅速发育并一直持续到果实成熟.胚的发育与果实的发育无明显竞争关系。