白菜类作物转基因技术研究进展

白菜类作物是芸薹属中重要的栽培亚种群,也是重要的蔬菜之一。建立高效可重复的植株再生和遗传转化体系是利用基因工程进行遗传改良所必需的。本文从高频率植株再生体系的建立,ＤＮＡ直接转移,不依赖于植物细胞或组织培养的农杆菌介导转移,建立在细胞或组织培养基础上的农杆菌介导的转化,转化株后代的遗传行为等方面论述了白菜类作物转基因技术的最新研究进展,并提出了存在的问题和进一步的研究方向。     

广西龙胜油茶枯叶蛾生物学特性研究

于 1995年至 1999年在广西龙胜县的油茶林内设 10块样地 (长×宽 =2 0 m× 2 0 m )观察油茶枯叶蛾 (L ebedanobilis Walker)的生活历期和习性 ,并从林间采回卵、幼虫、蛹、成虫于纱笼中饲养观察油茶枯叶蛾的生活史 ,以及各世代蛹、成虫、卵、幼虫出现期和终期。结果表明 ,在广西龙胜县 1年 1代 ,以初孵幼虫在卵壳内越冬 ,翌年 3月中旬当气温升至 18℃～ 2 2℃时 ,幼虫破壳而出 ;幼虫 7龄 ,发育历期 12 0 d～ 15 0 d。5龄开始食量增加 ,6龄～ 7龄为暴食阶段 ,油茶枯叶蛾幼虫一生食叶量 30 0片～ 35 0片 ,其中 4龄以前 2 0片～ 2 5片 ,5龄 30片～ 40片 ,6龄6 0片～ 10 0片 ,7龄 16 0片～ 170片 ,特别是 7龄 ,其食叶量约占终生食叶量的 70 %。8月中旬开始吐丝结茧 ,9月下旬至 10月上旬成虫羽化。     

PB—g—SAN弹性体对SAN树脂的增韧

采用种子乳液聚合法在聚丁二烯（PB）乳胶粒上接枝共聚苯乙烯和丙烯腈。合成了PB含量为40％的PB-g-SAN共聚物粉料。将其与SAN树脂熔融共混制得了一系列不同组成的ABS树脂,研究了共混物的力学性能、加工性能和形态结构。结果表明,在SAN树脂中随着PB-g-SAN含量的增加,共混物的冲击韧性和断裂伸长率不断提高,而拉伸强度和熔融指数出现下降的趋势。形态结构研究结果表明,PB橡胶粒子均匀地分散在SAN基体中,其粒径约为0．3μm,在橡胶粒子中含有大量的包容结构－SAN次级粒子。     

含偏差变元 Volterra 型积分方程解的存在性与渐近性

讨论一类含偏差变元Voherra型积分方程解的存在与渐近问题，利用Banach空间中的非紧性测度和不动点定理，建立了方程有形如z（t）=o（exp（ML（t）））解的充分条件，并给出一个例子说明结论的应用．     

Natural history of an ant–plant–butterfly interaction in a Neotropical savanna

Non-myrmecophilous lepidopteran larvae using plants bearing ant attractants such as extrafloral nectaries are good models for studying morphological and behavioural mechanisms against ant predation. Udranomia spitzi (Hesperiidae) is a butterfly whose larvae feed on leaves of Ouratea spectabilis (Ochnaceae), a plant with extrafloral nectaries. We described the early stages of U. spitzi, and used field observations and experiments to investigate the defensive strategies of caterpillars against predatory ants. Larvae pass through five instars and pupation occurs inside larval leaf shelters. Ant-exclusion experiments revealed that the presence of ants did not affect significantly caterpillar survival. Predation experiments showed that vulnerability to ant predation decreased with increase in larval size. The present study showed that predatory ants are not as relevant as demonstrated for other systems, and also illustrates how observational data and field experiments can contribute to a better understanding of the biology and ecology of a species of interest.     

Infestation by the freshwater cymothoid Artystone trysibia Schioedte (Crustacea,Isopoda): parasite and host behaviour

To observe the behaviour of cymothoid isopods during the infestation process, 30 experiments in aquaria were carried out, using the fish Gymnogeophagus gymnogenys (Hensel, 1870) and Jenynsia multidentata (Jenyns, 1842) as hosts, and Artystone trysibia Schioedte, 1866 as the parasite. All the specimens were collected from Guaíba Lake in Porto Alegre, Rio Grande do Sul. We recorded and analysed the behavioural acts of the parasites and hosts from the moment of encounter to the infestation, which was considered to be completed when the parasite had inserted itself into the fish's body. The behavioural acts are shown as a flow diagram, including the frequencies of occurrence of each act. Positive infestation occurred in 60% of the experiments. No relationship was observed between the sizes of the parasite and host, and the success of the infestation.     

Is it all death feigning? Case in anurans

Anurans are known to feign death as a way to avoid or minimize the risk of predation. However, information on this defensive strategy is scattered and we believe that there is more than one behaviour type referred to as thanatosis. Here we review the literature, add original data, and propose definitions and new names that complement the present knowledge on the subject. We collected information on 334 individuals of 99 species in 16 families and grouped the recorded displays into two categories of tonic immobility: (1) thanatosis, death-feigning, or playing possum, and (2) shrinking or contracting. These two categories are treated as different behaviour types because of the display pattern (position of fore- and hindlimbs, eye opening), presence of skin toxins (shrinking is mostly displayed by toxic species, whereas thanatosis is mostly displayed by non-toxic species), social context (interaction with predators), and their putative or actual functions.     

Mating behaviour in the bees,Dieunomia heteropoda and Nomia tetrazonata,with a review of courtship in Nomiinae (Hymenoptera: Halictidae)

Males of many bees in the subfamily Nomiinae (Halictidae) have numerous secondary sexual characters, which provide much systematic information. Similarly, the use of these structures by males during sexual behaviour may provide useful characters, but the courtship and copulatory behaviour of most of these bees is not known. Structures and behaviour used for courtship and mating are described for two species of nomiine bees, Dieunomia heteropoda and Nomia tetrazonata, along with brief observations of mating in a parasitic bee, Triepeolus verbesinae (Apidae: Nomadinae). A review of mating behaviour within the Nomiinae shows no obvious phyletic patterns, based upon present limited knowledge. The species-specific nature of the male secondary sexual characters suggests they may have evolved in the context of sexual selection, but behavioural data from populations of additional species are needed to evaluate the hypothesis adequately.     

Thanatosis in freshwater anomurans (Decapoda: Aeglidae)

The present study evaluated the occurrence of thanatosis in freshwater crustaceans. The duration of the thanatosis events was compared with respect to photoperiod and size for Aegla longirostri (Brazil) and Aegla denticulata denticulata (Chile). Adults of A. longirostri did not show thanatosis; juveniles were responsive only when they were out of water. In the two species, thanatosis occurred in both light and dark photophases, and there was no significant difference in the duration of the events between the photophases. For A. d. denticulata, which lives in deep waters and in sympatry with larger decapods, this behaviour seems to represent an adaptation either to the environment or to the biotic community of the species. This behaviour is apparently not necessary for adults of A. longirostri, since this species is mainly nocturnal in its adult phase and its activity rhythms do not coincide with those of its potential predators.