成都平原蔬菜生产中灌溉水对农药渗漏的影响研究

针对成都平原蔬菜生产中大量施用农药、大量灌水的特点,首次在国内应用欧洲官方成熟的农药评估模型——PEARL模型,研究评估了成都平原当前蔬菜生产中的灌溉方式对两种不同特性农药的渗漏的影响。杀毒矾(土壤吸附力(KOM)为0 L/kg,半衰期(DT50)为80 d)在没有灌溉条件下,其渗出土体时的最大质量浓度是190μg.L-1,而有灌溉条件下其渗出质量浓度则可达523μg.L-1,是没有灌溉条件下的2.75倍。三唑磷(KOM为200 L.kg-1,DT50为60 d)在没有灌溉条件下,其渗出土体时的最大质量浓度是0.025μg.L-1,而有灌溉条件下其渗出质量浓度为0.13μg.L-1,比没有灌溉时提高了4.2倍。不管有没有灌溉三唑磷在该地区对地下水的污染风险都很小,而杀毒矾的风险则很高。因此,农药的化学特性是影响农药渗漏的最重要的因子。在蔬菜生产中应尽量选用被土壤吸附力强、半衰期短的农药,例如:三唑磷;农药在土壤中的移动载体是土壤水,不合理的灌溉会大大地加大农药淋溶,应当多使用微喷、滴灌等节水灌溉措施,减少使用漫灌等耗水多的原始灌溉方式。     

GC-EAG-analysis of volatiles from Brussels sprouts plants damaged by two species of Pieris caterpillars: olfactory receptive range of a specialist and a generalist parasitoid wasp species

Summary. Feeding by Pieris brassicae or P. rapae caterpillars on Brussels sprouts plants induces the emission of synomones that attract natural enemies of the caterpillars, Cotesia glomerata, a generalist parasitoid, and C. rubecula, a specialist on P. rapae. Previous research on this tritrophic system has identified a large number of volatiles in the headspace of herbivore-damaged Brussels sprouts plants, and this paper addresses the question which of these volatiles are perceived by the two parasitoid species. Headspace odors from both P. brassicae- and P. rapae-damaged Brussels sprouts plants were analyzed by coupled gas chromatography electro- antennogram (GC-EAG) detection. Twenty volatiles evoked consistent EAG reactions in the antennae of both species and nineteen of these volatiles could be identified with GC-MS. One component that could not be identified due to its low concentration, evoked EAG responses in antennae of C. rubecula only. Possible consequences for searching behavior of the two parasitoid species are discussed.     

Multiple trans-Arctic passages in the red alga Phycodrys rubens: evidence from nuclear rDNA ITS sequences

In order to investigate how episodes of geological and climatic change have influenced the distribution and evolutionary diversification of Arctic to cold temperate-North Atlantic seaweed species, intraspecific genetic variation was analyzed among isolates of the sublittoral, benthic red alga Phycodrys rubens (collected between June 1992 and January 1994). Rooted phylogenetic analyses of nuclear ribosomal DNA internal transcribed spacer (ITS) sequences and the plastid encoded Rubisco spacer sequences suggest that P. rubens invaded the North Atlantic from the Pacific shortly after the opening of the Bering Strait (3 to 3.5 million years ago), colonizing both the western and eastern Atlantic coasts. Based on these data we further hypothesize that P. rubens survived along the European coasts during the more recent Pleistocene glaciations, while becoming locally extinct along the North American Atlantic coasts. Following retraction of the last ice sheet, the western Atlantic coast was colonized a second time from the Pacific. The presence of two distinct genetic types (based on ITS and Rubisco sequences) along the European coasts is postulated to be a result of isolation and subsequent differentiation. This is likely because ice-free areas are known to have existed in northern Scotland and Norway during the last glaciation. The presence of an East Atlantic genetic type along the West Atlantic coast is believed to be a recent introduction (caused by human activity) of P. rubens to Newfoundland.     

The Impact of the Hyperacid Ijen Crater Lake. Part I: Concentrations of Elements in Crops and Soil

In Asembagus (East Java, Indonesia) irrigation water is contaminated with effluent from the hyperacid Ijen Crater Lake resulting in a low pH and high levels of various elements. As a first step towards a risk assessment, locally produced food items (rice, maize, cassava leaf, cassava root, peanuts) were collected and concentrations of As, B, Ca, Cd, Co, Cu, Fe, Mg, Mn, Mo, Ni, Pb, V, Zn were compared to samples from a reference area and with literature values. Further, concentrations in rice were compared to total soil concentrations in paddy fields. Compared to the reference area, food items produced in the contaminated area had increased levels of Cd, Co, Ni and Mn in particular, while levels of Mo were lower. In contrast, total soil concentrations of Cd and Mn in particular have decreased whereas especially Mo was increased. In combination with the observed soil acidification, it is likely that the bioavailable concentration of most elements in the contaminated soil is higher (except for Mo) due to an increased weathering rate and/or input via the contaminated irrigation water. In terms of human health, concentrations in foods were generally within normal literature values. However, it was observed that essential elements (in particular Fe) known for their inhibitory effects on e.g. Cd and Mn toxicity did not accumulate in crops whereas Cd and Mn did.     

Recognition of individual-specific marked parasitized hosts by the solitary parasitoid Epidinocarsis lopezi

Summary In parasitoid wasps, self-superparasitism (oviposition into a host already parasitized by the female herself) often contributes less to the reproductive success of the parasitoid than oviposition into a host previously parasitized by a conspecific (conspecific superparasitism). It could therefore often be profitable for parasitoids to avoid self-superparasitism. This requires a mechanism for either (1) the avoidance of previously searched areas and/or (2) the rejection of hosts containing eggs laid by the searching female. We investigated whether the solitary parasitoid Epidinocarsis lopezi is able to avoid self-superparasitism. We show that visits to previously searched patches were shorter than visits to unsearched patches and conclude that E. lopezi females leave a trail odour on patches they have searched. No differences were found between the time on patches previously searched by the wasp itself and on patches visited by conspecifics. However, E. lopezi superparasitizes fewer hosts previously parasitized by itself than hosts parasitized by a conspecific. Thus, they recognize an individual-specific mark in or on the host. We discuss how patch marking and host marking enable E. lopezi to avoid self-superparasitism.     

Competitive regimes and female bonding in two species of squirrel monkeys (Saimiri oerstedi and S. sciureus)

Summary Ecological and behavioral data from long-term field studies of known individuals in two closely related squirrel monkey species (Saimiri oerstedi and S. sciureus) were used to examine hypotheses about the source of variation in female bonding among group-living primates. Social relationships in species which live in cohesive groups are thought to depend on the nature of competition for resources. S. oerstedi and S. sciureus both live in large groups and are subject to intense predation. Direct feeding competition both between and within groups is extremely low in S. oerstedi; in this species female relationships are undifferentiated, no female dominance hierarchy is evident and females disperse from their natal group. S. sciureus also experiences very low levels of between-group competition, but within-group direct competition for resources is frequent; this species demonstrates differentiated female relationships, a female dominance hierarchy, and female philopatry. The correlated ecological and social variables found in these two congeners further minimize the minor effects of phylogenetic differences and emphasize the importance of food distribution in determining social characteristics. Offprint requests to: S. Boinski