Effects of irradiation level on leaf growth of sunflower

Sunflower, Helianthus annuus L. cv. INRA 6501, plants were grown in a gravel culture subirrigated with Hoagland nutrient solution, at photosynthetically active radiation levels of 15, 30 and 60 W m^-2 at a daylength of 16 h, a temperature of 20°C and a relative humidity of 60% throughout. Development of the plant and growth of the leaves were measured. High irradiance accelerated development proportionally in all phases from germination, through leaf initiation, primordial flower formation and the maturation of all plant organs until anthesis. High irradiance levels stimulated the expansion of the growing shoot, which produced more and larger primordia. Under constant conditions the ratio between leaf initiation rate and mature length of a leaf remained constant, although the growth patterns [relationship between relative growth rate (RGR) and organ age] of successive leaves were not similar. Consequently, it may be assumed that, as in poplar, the increasing size of the growing shoot reflects the increase of the vascular system of sunflower. The growth patterns of the leaves depend on the developmental stage of the plant and, in the young primordial stage, also on irradiance level. In the linear phase of growth the growth pattern is independent of irradiance level.     

紫胶虫最佳生长地的植被条件分析

本文在对紫胶产区进行调查的基础上,分析了云南紫胶虫最佳生长地的植被条件、对其中的四种群落类型从植物种类成分、群落结构和群落生态等方面进行分析。根据丰富的寄主资源和有利于紫胶虫越冬的气候条件指出“暖热性稀树灌草丛”及“河谷季雨林次生林和灌丛”是云南紫胶虫及其主要寄主植物的适生类型。本文在总结紫胶产区的经验基础上,提出了开发利用的意见和改造的措施。     

Biomass and production of Argyrodiaptomus furcatus,a tropical calanoid copepod in Broa Reservoir,southern Brazil

The biomass and the production of Argyrodiaptomus furcatus (Sars), the most abundant copepod in Broa Reservoir (São Carlos, São Paulo State), were estimated, determining in the laboratory the development time and the quantity of organic carbon and establishing the relationship between these two parameters. The daily production was calculated from P = B(1- e^gt) and the annual production was obtained by integrating daily production against time. The maximum production of Argyrodiaptomus furcatus in the reservoir depends on the region considered and on the period of the year. The maximum production was 45.15 mg C m^–3d^–1 in March, 1976 at station II, region of macrophytes and 6.74 mg C m^–3d^–1 at station IV, near the dam. The mean production for the year is 6.26 mg C m^–3d^–1 at station II and 1.43 mg C m^–3d^–1 at station IV.     

Formation of the ventral hooks on the sperm head of the plains mouse,Pseudomys australis

The sperm head of the plains mouse, Pseudomys australis, has three curved hooks projecting from its anterior margin. The two ventral hooks have previously been shown to consist largely of an extension of the subacrosomal material. To characterize further the structure and composition of the ventral hooks, we have examined their formation during spermiogenesis using transmission electron microscopy, silver staining, and actin localization with NBD-phallacidin. The ventral hooks develop as an extension of the perinuclear space and postacrosomal dense lamina on the anteroventral margin of the sperm head. Bundles of 6-nm-thick filaments appear in the core of each hook; these are probably actin filaments based on staining of the hooks with NBD-phallacidin. Just prior to spermiation, electron-dense material condenses in the core of the ventral hooks and concurrently in the perinuclear space in the remainder of the sperm head. The two ventral hooks thus appear to consist of a core of perinuclear material and actin filaments, which is enclosed by a continuation of the postacrosomal dense lamina.     

Location of a second partitioning region (ParL) on the F plasmid

Abstract The leading region of the F plasmid has been found to extend the maintenance of the normally unstable plasmid vector pACYC184. This ability is due to effective partitioning of plasmid molecules at cell division. Cloning, deletion analysis and transposon mutagenesis have located the partitioning region (ParL) to be encoded within 63.65–64.11F. Complementation studies indicated that parL is a cis -acting locus.     

人14p＋标记染色体的分子细胞遗传学研究

一例23岁女性患者因近五、六年来出现胡须、四肢多毛及偶有月经不规则而就诊。细胞遗传学检查发现一个短臂明显增大的亚中着丝粒的14号标记染色体14p ·p 区域GTG显带呈浅染,C-带暗染,都呈均匀的染色区。硝酸银染色在p 远侧端显现一个Ag-NOR,其大小与正常近端着丝粒染色体的无明显差异。应用~3H标记的7.3 kb长的rRNA基因探针进行染色体原位杂交,自显影银颗粒沿整个p 区域分布,p 上的银颗粒数是正常近端着丝粒染色体短臂上银颗粒平均数的5倍。这些结果排除了Y或其他染色体参加的重排形成p 的可能性,并表明Ag-NOR的大小或NOR的数目并不一定与rRNA基因的数量成正比。研究Dp 或Gp 类型的染色体变异,对了解人二倍体细胞内rRNA基因表达的调控有重要意义。     

Discrepancy in divergence of the mitochondrial and nuclear genomes ofDrosophila teissieri andDrosophila yakuba

Summary Restriction sites were compared in the mitochondrial DNA (mtDNA) molecules from representatives of two closely related species of fruit flies: nine strains ofDrosophila teissieri and eight strains ofDrosophila yakuba. Nucleotide diversities amongD. teissieri strains and amongD. yakuba strains were 0.07% and 0.03%, respectively, and the nucleotide distance between the species was 0.22%. Also determined was the nucleotide sequence of a 2305-nucleotide pari (ntp) segment of the mtDNA molecule ofD. teissieri that contains the noncoding adenine+thymine (A+T)-rich region (1091 ntp) as well as the genes for the mitochondrial small-subunit rRNA, tRNA^f-met, tRNA^gln, and tRNA^ile, and portions of the ND2 and tRNA^val genes. This sequence differs from the corresponding segment of theD. yakuba mtDNA by base substitutions at 0.1% and 0.8% of the positions in the coding and noncoding regions, respectively. The higher divergence due to base substitutions in the A+T-rich region is accompanied by a greater number of insertions/deletions than in the coding regions. From alignment of theD. teissieri A+T-rich sequence with those ofD. yakuba andDrosophila virilis, it appears that the 40% of this sequence that lies adjacent to the tRNA^ile gene has been highly conserved. Divergence between the entireD. teissieri andD. yakuba mtDNA molecules, estimated from the sequences, was 0.3%; this value is close to the value (0.22%) obtained from the restriction analysis, but 10 times lower than the value estimated from published DNA hybridization results. From consideration of the relationships of mitochondrial nucleotide distance and allozyme genetic distance found among seven species of theDrosophila melanogaster subgroup, the mitochondrial nucleotide distance observed forD. teissieri andD. yakuba is anomalously low in relation to the nuclear genetic distance.