Chorology of the Euxinian and Hyrcanian element in the woody flora of Asia

The Euxinian and the Hyrcanian floristic province are analysed in respect to their trees and shrubs. These provinces mark the southern limit of the Euro-Siberian Region in SW. Asia. Mesophyllic forests dominate; they are deciduous, but there is a substantial component of evergreen shrubs in the understorey. Characteristics species frequently have a relic nature. Species lists and some exemplary distribution maps are presented for the Euxinian and the Hyrcanian element, both with endemic and more wide-spread species, including the characteristic Euxine-Hyrcanian group.     

Evolution of the Australian flora through the Tertiary

The evolution of the Australian flora through the Tertiary has not been reviewed by a megafossil palaeobotanist for almost a century. Based on material available and published studies, the Australian Tertiary can be considered in three units: Eocene, Oligo-Miocene, and Pliocene. Key taxa in the Eocene includeCasuarinaceae, Proteaceae, Fagaceae, Podocarpaceae, andLauraceae. Many known Eocene deposits are interpreted as warm, humid rainforests.Oligo-Miocene floras reflect a climatic deterioration, with greater occurrence of sclerophylly and xerophylly. A reduction of tropical taxa is seen with an increase ofMyrtaceae and earliest records ofMimosaceae, Chenopodiaceae, andPoaceae. These trends continue into the Pliocene, which is not well represented in Australia.Problems needing to be addressed include the discrepancy between the pollen and megafossil records ofNothofagus, the origins of Australia's wet tropical taxa, and the role of fire in the early evolution of the Australian flora.     

Body shape and differences between species

The variation of body shape among prosimians is reviewed. Special emphasis is placed on the selective advantages, that is the mechanical reasons, to which variants of the locomotor apparatus can be traced back. There are differences found in the cheiridia, but at present they cannot be explained in terms of mechanics; there is nearly no knowledge about the mechanical meaning of their diversity. Myological characteristics of taxa can be explained mechanically, but this has not yet been done. Well known are variations of body proportions. These discriminate higher taxa, and are largely coincident with the often-used locomotor categories. In spite of this, there are only few sound arguments about the real biomechanic value of characteristic proportions for a given locomotor mode. What is known on this field, is reviewed. Progress can be made only, if the mechanical conditions, set by postural behavior and locomotion, are understood completely. The subtle distinctions between lower taxonomic units can normally be identified only on the basis of detailed and quantified analyses of movements on one hand, and of biometrics on the other. In the few cases in which such studies have been made, the differences of morphology fit to the mechanical requirements of locomotion which also differ only in quantitative details.     

向日葵离体孤雌生殖的超微结构研究

本文是研究未受精胚珠培养诱导的孤雌生殖过程超微结构变化的首次报道。向日葵(Heliaanthus annuus L.)的卵细胞在离体条件下被激活,发生细胞核移位、极性丧失、细胞器增多并转变成活动状态、液泡化程度增大、合点端形成细胞壁等一系列变化,预示即将启动孤雌生殖。孤雌生殖的原胚具有若干显著特征,如极性颠倒、有自体吞噬活动、壁的自由生长、游离核分裂等。对这些现象作了初步的讨论。     

甘蔗叶不同部位ATP酶活性细胞化学定位

甘蔗叶片,叶鞘和肥厚带韧皮部 ATP 酶活性定位于筛管、伴胞的质膜、内质网和某些伴胞细胞基质、小囊泡和发育成熟的液泡上;叶片韧皮部薄壁细胞、厚壁细胞和厚壁通道细胞质膜及小囊泡中亦显示有 ATP 水解产物;维管束鞘细咆与厚壁细胞或厚壁通道细胞所构成的细胞间隙上也存在有 ATP 酶活性反应产物沉淀。甘蔗叶片大、中、小三种维管束,从小维管束到大维管束,面向细胞间隙的细胞表面上的 ATP 酶活性逐渐增强,而维管束鞘细胞质膜上的 ATP 酶活性则趋于减弱;同一维管束内则以韧皮部细胞的 ATP 酶活性最强。维管束鞘细胞与叶肉细胞之间存在很多的胞间连丝,并表现出高的 ATP 酶活性。讨论了 ATP 酶活性的分布状态与叶肉细胞的光合产物向韧皮部运输的关系。     

南京地区繁缕和小繁缕群体的研究

繁缕(Stellaria media)和小繁缕(S.apetala)是两个形态相似的近缘种,有人把后者作为前者的亚种或变种来处理。本文通过对南京地区不同生境的三个自然群体和三个人工控制栽培群体的取样,以群体为单位,分别测算了叶、萼片、雄蕊、花瓣、果实和种子的8个数量性状的变异,绘制了多角形图;对花粉粒和种子进行了扫描;还通过花蕾套袋试验对种子活力作了检查。结果发现繁缕和小繁缕都是近亲繁殖植物,在形态上区别明显,对生态环境的要求基本相同,但小繁缕似更能耐受人为的践踏和刈割。     

似哺乳类爬行动物和哺乳类动物脑颅侧壁构造类型的演替

本文对从原始似哺乳爬行动物进化到高级兽类哺乳动物过程中脑颅侧壁所发生的形态演化进行了分析,根据构造上的不同,将这些动物的脑颅侧壁的构造方式划分为四个构造类型,代表四个进化阶段。     

贵州普定白岩脚洞石片的初步研究

本文对贵州普定白岩脚洞遗址中所获的1220件石片进行了分类观察。根据石片背面石皮的保存情况,疤与疤之间的关系,背疤的受力部位与石片台面的关系等特征,可从一个侧面反映出石核的利用率较高。     

长江中游鱼类寄生棘头虫区系的研究

经过3年10次调查,剖检湖北省宜都、黄冈两处江段所产72种鱼类,共计766尾。收集棘头虫10种,其中包括2新种和1新组合,即蛇鮈新棘吻虫(新种)Neoechinorhynchus saurogobi sp.nov.,长江丽棘虫(新种)Brentisentis yangtzensis sp.nov.(Illiosontidae),鲤丽棘虫(新组合)B.cyprini comb.nov.。对长江中游鱼类寄生棘头虫区系的特点进行了分析和探讨。     

Induction of ?2 frameshift mutations within alternating GC sequences by carcinogens that bind to the C8 position of guanine residues Development of a specific mutation assay

Summary Using a forward mutation assay we have previously found that N-2-acetylaminofluorene (AAF), a strong chemical carcinogen, induces a majority of frameshift mutations located at specific sequences called mutation hot spots. Among these hot spot sequences, the NarI sequence (GGCGCC), is specific for –2 frameshifts (GGCGCC) GGCC). Interestingly, these frameshift mutations occur independently of a functional umuDC locus. Being interested in elucidating this mutation pathway we have developed a reversion assay that is specific for this class of mutations. The assay is based on the reversion of a +2 frameshift mutant of plasmid pBR322 from tetracycline sensitivity to tetracycline resistance. It is shown that only true reversion events lead to tetracycline resistance. The carcinogen AAF induces this reversion event at a frequency that is increased four- to fivefold over the background frequency. A series of chemical carcinogens which, like AAF, bind covalently to the C8 position of guanine, are compared for their efficiency to induce this specific mutation event. Large variations in the mutagenic efficiency of these chemicals are observed and discussed in terms of the anti/syn conformation of the carcinogen-modified guanine residue. Based on this test, we describe a convenient spot assay that this presently used in our laboratory to isolate Escherichia coli mutants affected in this mutation pathway.