诺氟沙星对芽期玉米的毒性和氧化损伤研究

畜禽养殖废弃物的农田处置,使大量抗生素进入环境,从而对环境生物产生潜在危害.为了研究诺氟沙星(norfloxacin,Nor)对玉米发芽和幼苗生长的影响,采用水培发芽实验,测定了不同浓度下,诺氟沙星对玉米种子的发芽率和玉米幼苗对诺氟沙星的吸收与传输的影响;另外还研究了诺氟沙星对玉米幼苗生物量、自由基水平、丙二醛(MDA)含量、抗氧化酶活性的影响.结果显示,诺氟沙星能被玉米根吸收并传输到地上部分.0.5mg·L-1～50mg·L-1的诺氟沙星暴露均不影响玉米的发芽率.当诺氟沙星浓度大于1mg·L-1时,幼苗的生长受到抑制,其敏感指标依次为根重>根长>芽长>芽重.诺氟沙星暴露使玉米根、芽中MDA含量明显增加,玉米根中谷胱甘肽硫转移酶(GST),过氧化物酶(POD),超氧化物歧化酶(SOD)和过氧化氢酶(CAT)等抗氧化酶的活度有显著改变,这表明诺氟沙星暴露能够引起玉米体内的氧化损伤.用电子自旋共振结合二级自由基自旋捕获技术测定了玉米根中自由基水平,发现诺氟沙星能够引起玉米根中大量羟基自由基的产生,为诺氟沙星引起玉米幼苗的氧化损伤提供了直接的证据.     

Foraging behavior of juvenile Carcinus maenas (L.) and Cancer pagurus L.

Information concerning the way juvenile crabs choose their diet from a variety of prey types can be useful for a better understanding of community dynamics, as well as for the adequate management of natural resources. Prey size and species selection by juvenile Carcinus maenas (15-35 mm carapace width, CW) and Cancer pagurus (20-40 mm CW) feeding on four bivalves of contrasting shell morphology were investigated. When offered a wide size range of Mytilus edulis, Ostrea edulis, Crassostrea gigas, and Cerastoderma edule presented individually, crabs generally showed evidence of size-selective predation. Cancer pagurus selected larger mussels relative to the size of their chelae (relative prey size, RPS) than did Carcinus maenas of similar and even larger carapace width. However, the RPS of selected O. edulis and Cerastoderma edule were similar for all crabs, suggesting that certain prey features constitute effective barriers even to the powerful chelae of Cancer pagurus. When offered a wide size range of mussels and oysters simultaneously, all crabs consistently selected mussels. When offered O. edulis and Crassostrea gigas, crabs consumed both these oyster species in similar numbers. Carcinus maenas consumed similar numbers of mussels and cockles; Cancer pagurus, however, showed no preference for either prey in the smaller size classes but selected more mussels than cockles as prey increased in size. Although previous studies report that adult Carcinus maenas select prey species according to their profitability (amount of food ingested per unit of handling time, milligrams per second), consumption rates of the size classes of prey selected by juvenile shore crabs did not always parallel prey value. Although variations in crab strength can account for many of the differences between the foraging strategy of juvenile and adult C. maenas, our results suggest that juvenile crabs are less species selective than adults as a result of the restrictions imposed on small individuals that have limited access to larger prey.     

Topology of Extinction and Endangerment of Native Fishes in the Pacific Northwest and California (U.S.A.)

Recent studies have provided a broad data base on extinction and endangerment of species, subspecies, and distinct populations of inland fishes in western North America. Development of a synoptic, regional-scale image of extinction and risk of extinction is complicated by the small size and linear distribution of fluvial aquatic habitats and by interspecific variation in areal extent of populations. I developed a regional map of extinction-risk isopleths based on the number of extinct and persistently declining species in drainage basins of the Pacific Northwest and California. This topological synthesis is useful for delineating and monitoring areas of historic and ongoing loss of aquatic biodiversity, and for relating losses to patterns of land use and habitat modification, climate hydrology, and geomorphology. From an ecological perspective, endangerment of numerous indigenous populations of seven widely distributed species of anadromous salmonids in this region is as important as the more local, diffuse effects of declines in more than 60 endemic, nonanadromous species and subspecies. The simultaneous decline of numerous taxa in basins not afflicted with dams or diversions suggests that cumulative damage to aquatic habitats caused by logging, grazing, urbanization, and other land uses plays a major role in icthyofaunal impoverishment.     

Permanence of Euscorpius carpathicus (L.) larvae on the mother's back (Scorpiones,Chatidae)

Summary The tendency of Euscorpius carpathicus larvae to remain on immobilized live or dried scorpions of the same or different species (Euscorpius flavicaudis) has been tested. Dried scorpions are less attractive than live ones, which are equally attractive regardless of species, sex or reproductive phase. The larvae find old (one year) dried specimens less attractive than freshly or recently (15 days) killed females, which are equally as attractive as live mothers (Table 1). A substratum treated with a chloroform extract of the mother's cuticle is consistently preferred by the larvae. The maternal behaviour (tolerating the larvae on the back) usually disappears about a week after the moult of the larvae, but it can be protracted if they are continually replaced by younger larvae (Table 2). The survival rate of larvae on live mothers is higher than on dried specimens.     

Metalaxyl effect on nitrogenase activity (acetylene reduction) and yield of mungbean (Vigna radiata (L.) wilzek)

In an experiment, application of different levels of metalaxyl to a sandy loam soil significantly affected the nodulation and nitrogenase activity of mungbean. In both the compost amended and unamended soils, 0.5 mg kg(-1) of metalaxyl enhanced acetylene reduction activity and yield of mungbean, where as higher concentrations (1 mg and 2.5 mg kg(-1) of fungicide) inhibited the nodulation traits as well as economic traits of mungbean.     

Survival and growth of transplants of laboratory raised axenic seedlings of Enhalus acoroides (L.f.) Royle and field-collected plants of Syringodium isoetifolium (Aschers.) Dandy, Thalassia hemprichii (Ehrenb.) Aschers. and Halodule pinifolia (Miki) den Hartog

Experimental transplantation investigations, using laboratory raised axenic seedlings of Enhalus acoroides and natural populations of Syringodium isoetifolium, Thalassia hemprichii and Halodule pinifolia in the Gulf of Mannar Marine Biosphere Reserve, found that the denuded seagrass ecosystem of this Gulf can effectively be restored with plug and turfs methods of seagrass transplantation. Axenically developed E. acoroides, transplanted by the staples method, established by adapting to the prevailing environmental conditions. 0% seedlings “washed ashore” when the staples method was adopted using ‘L’ shaped bamboo sticks for transplanting E. acoroides and S. isoetifolium seedlings. This suggests that the seagrass transplantation using “L” shaped bamboo sticks, as staples will be technically feasible and eco-friendly for future seagrass transplantation programmes. Substratum type, duration of low tide exposure and environmental parameters like surface water temperature and turbidity are key parameters determining the success of the transplantation attempts.     

Variation in copulation duration and the resultant degree of sperm removal inOrthetrum cancellatum (L.) (Libellulidae: Odonata)

Summary Orthetrum cancellatum showed two distinct copulation durations at a study site in the south of France. These different durations are correlated with different degrees of sperm displacement from the female sperm stores; long copulations (894±142 s) resulting in almost 100% sperm removal, and short copulations (21.0±13.5 s) resulting in 10–15% removal. The difference in copulation duration is also related to the site of copulation and to the relative age of the copulating males. At oviposition sites males who gained copulations were relatively young and copulated for long periods. The difference in the duration of copulation and the degree of sperm removal is discussed with reference to the female habit of ovipositing before remating during oviposition episodes, and the possibility of differences in the rate at which males encounter receptive females at the two sites.     

Genetic Analysis of the Endangered Island Endemic Malacothamnus fasciculatus (Nutt.) Greene var. nesioticus (Rob.) Kearn. (Malvaceae)

Isozyme, randomly amplified polymorphic DNA, and ribosomal DNA analyses were used to evaluate the genetic distinctness and diversity of the endangered island endemic Malacothamnus fasciculatus var. nesioticus (Santa Cruz Island bush mallow). Analysis of amplified DNA profiles and electrophoretic data indicates that var. nesioticus is genetically distinct from other varieties within the species. No isozyme or amplified DNA variation was detected among individuals of nesioticus populations, but restriction site analysis of ribosomal DNA revealed the presence of three closely related genotypes within one of the nesioticus populations. Apparent clonal structuring was found in both nesioticus populations and in one mainland population, var. nuttallli . Results from these analyses provide the background necessary for the design of conservation efforts with recovery goals that insure the long-term survival of Malacothamnus fasciculatus var. nesioticus .     

镉胁迫对水车前叶片抗氧化酶系统和亚显微结构的影响

报道了模拟镉污染对水车前叶片抗氧化酶系统的影响及对叶细胞超微结构 ,主要是叶绿体、线粒体和细胞核的损伤情况。随胁迫程度的增大 ,超氧化物歧化酶活性和可溶性蛋白含量下降明显 ,丙二醛含量则上升 ,过氧化物酶和过氧化氢酶活性在 0 1mg/L浓度处达到最高后呈下降趋势。电镜观察结果表明 :毒害初期 ,叶绿体和线粒体膨胀 ,类囊体明显空泡化 ;高浓度镉处理使破坏程度加重 ,叶绿体被膜消失和叶绿体解体 ;线粒体间质溶解 ,濒临解体 ;细胞核染色质凝集并散入细胞质中。由于镉胁迫破坏了植物的抗氧化酶系统 ,并对超微结构造成不可逆损伤 ,最终使细胞死亡     

Field and Genetic Survey of the Endangered Butte County Meadowfoam—Limnanthes floccosa subsp. californica (Limnanthaceae)

The Butte County meadowfoam ( Limnanthes floccosa subsp, californica ), an endangered annual endemic to vernal pools in Butte County, California, is of agronomic interest as a sperm whale oil substitute. Because it is threatened by rapid development of the community of Chico, a field and genetic survey was required to guide a conservation program. Eight new populations were discovered, bringing the total known to eleven. Population sizes varied from 220 to 45,689 plants; mean seed set per flower, a bioassay of site quality, ranged from 0.82 to 2.56 among populations. The array of associated taxa, an indicator of appropriate habitat was fairly uniform across populations. Based on allozyme and morphometric data no introgression between L. floccosa subsp, californica and L. alba subsp, alba at sympatric sites was found. Populations were remarkably monomorphic, probably due to past population bottlenecks in conjunction with high selfing rates. Electrophoretic analysis of 28 isozyme loci revealed that 96% of total genetic diversity was distributed among populations. The migration rate, Nm , calculated from the mean frequency of private alleles, ( P (1)), and from the proportion of genetic variation distributed between populations, Gst , estimated exchange between local populations of one diploid individual every 50 to 100 generations, respectively. Mean genetic identity among populations was 0.91 ± 0.068. Grouping of populations on the basis of genetic distance identified two distinct populations and three clusters of populations that deserve high priority for preservation because they are likely to have high frequencies of locally adapted alleles. The low migration rates and substantial differentiation among populations suggest a conservation plan that emphasizes preservation of as many populations as possible, at possible expense of numbers of individuals.     

Sperm limitation and the evolution of extreme polyandry in honeybees (Apis mellifera L.)

Honeybee queens (Apis mellifera) show extreme levels of polyandry, but the evolutionary mechanisms underlying this behaviour are still unclear. The sperm-limitation hypothesis, which assumes that high levels of polyandry are essential to get a lifetime sperm supply for large and long-lived colonies, has been widely disregarded for honeybees because the semen of a single male is, in principle, sufficient to fill the spermatheca of a queen. However, the inefficient post-mating sperm transfer from the queens lateral oviducts into the spermatheca requires multiple matings to ensure an adequate spermatheca filling. Males of the African honeybee subspecies A. m. capensis have fewer sperm than males of the European subspecies A. m. carnica. Thus, given that sperm limitation is a cause for the evolution of multiple mating in A. mellifera, we would expect A. m. capensis queens to have higher mating frequencies than A. m. carnica. Here we show that A. m. capensis queens indeed exhibit significantly higher mating frequencies than queens of A. m. carnica, both in their native ranges and in an experiment on a North Sea island under the same environmental conditions. We conclude that honeybee queens try to achieve a minimum number of matings on their mating flights to ensure a sufficient lifetime sperm supply. It thus seems premature to reject the sperm-limitation hypothesis as a concept explaining the evolution of extreme polyandry in honeybees.Communicated by R.E. Page     

Comparison of growth performance of Lolium perenne L., Dactylis glomerata L. and Agropyron elongatum (Host.) P. Beauv. for erosion control in Turkey

This study was carried out in plastic containers to compare growth performances of perennial ryegrass, orchardgrass and tall wheatgrass to be given priority in revegetation studies in Turkey. Three pre-germinated seeds of each grass species were planted separately into the soil in the black plastic containers. Seedlings were harvested 2, 4 and 6 months after planting pre-germinated seeds and measured for percentage of seedling emergence, rooting depth, height growth, leaf and tiller development and shoot and root weights. Germination percentage was 97.8% for perennial ryegrass, 64.1% for orchardgrass and 11.6% for tall wheatgrass and perennial ryegrass had the greatest whereas tall wheatgrass had the lowest seedling emergence. Two months old rooting depth was 25.66 cm for perennial ryegrass, 20.56 cm for orchardgrass and 30.10 cm for tall wheatgrass. At the end of the study, perennial ryegrass developed about 104 tillers per plant while they were 21.4 and 36.6 tillers per plant for orchardgrass and tall wheatgrass, respectively. Orchardgrass produced greater shoot and root biomasses than tall wheatgrass and similar to perennial ryegrass. All these meant that perennial ryegrass had a better growth performance than orchardgrass and tall wheatgrass to be used for erosion control.     

The effects of feeding by the black bean aphidAphis fabae Scop. (Homoptera: Aphididae) on copper and cadmium accumulation in broad bean (Vicia faba L.)

Broad beans (Vicia faba L.), cultured hydroponically were supplied with 100 g mL^–1 copper or 50 g mL^–1 cadmium in nutrient solution. Samples of plant material from both nutrient regimes were analysed before and after infestation by the black bean aphid (Aphis fabae Scop.). Heavy aphid infestation resulted in a significant reduction in copper content of shoots in comparison with uninfested plants. A similar, but less well- defined, situation occurred in the case of cadmium.Further investigations examined the effects of different levels of aphid infestation on the above phenomena. In all cases the presence of feeding aphids reduced elemental accumulation in plant shoots. Long term infestation with population densities as low as three adult aphids showed a reduction in shoot copper and cadmium content.     

Respiratory impairment by water-borne copper and zinc in the edible crab cancer pagurus (L.) (Crustacea: Decapoda) during hypoxic exposure

Specimens of the edible crab Cancer pagurus (L.) collected in the Skagerrak, Denmark, between June and August 1990 were examined in the laboratory. Impairment of respiratory function after pre-exposure (7 d) to sub-lethal concentrations of Cu and Zn (0.4 mg l^-1) was only detectable during hypoxic exposure [PO₂ (partial pressure of oxygen) =60 torr]. This was indicated by a decrease in the transfer factor (TO₂), due principally to an increase in the PO₂ differential across the gills. Cu and Zn exposure did not cause significant changes in ventilation or perfusion although there was some indication that cardiac output may increase in respiratory-impaired individuals. After 28 d exposure no difference was noted in the respiratory responses to hypoxia of treated and untreated crabs. It is concluded that respiratory impairment was due to an increase in the diffusion barrier thickness at the gills and that this was reversible even during continued exposure to trace metal contamination.     

The influence of temperature on the territorial and mate locating behaviour of the small heath butterfly,Coenonympha pamphilus (L.) (Lepidoptera: Satyridae)

Summary Individual Coenonympha pamphilus males shifted mate locating behaviour depending on temperature. Under low temperature conditions males competed for territories, resulting in a high proportion of potential territories being occupied by stationary males and in long interactions between males in teritories. When temperatures became higher, stationary males tended to leave their territories and travel over a wider area, i.e. become vagrant. This resulted in a low proportion of territories being occupied by stationary males and inshort territorial interactions. Males could stay longer in flight without perching and hence also search a larger area for females within a given time span with increasing temperatures. This may explain why males adopt vagrant behaviour at higher temperatures. Al lower temperatures, on the other hand, when males cannot search effectively for females, waiting for them at a defended territory should be the most successful strategy.     

EDU对臭氧胁迫下菠菜急性伤害症状和光合特性的影响

如何减轻近地层臭氧(O3)体积分数持续升高对作物的影响是污染生态学研究的热点之一。运用改进的开顶式气室(open-top chambers,OTCs)装置,对嘉兴尖叶、嘉兴圆叶和荷兰35三种菠菜(Spinacia oleracea L.)进行连续5 d,每天8 h的臭氧急性暴露处理,且在暴露前24 h喷施300 mg.L-1质量浓度抗氧化剂ethylenediurea(EDU),研究EDU对臭氧胁迫下菠菜急性伤害症状及光合特性的影响。结果表明:(1)菠菜暴露于高体积分数O3时,叶片出现失水干枯、坏死斑等急性伤害症状,光合色素含量、气体交换参数和光响应参数显著降低,且下降幅度和暴露体积分数呈正相关。(2)菠菜经EDU处理后,光合特性参数明显提高。对O3和EDU作双因子分析发现,随着臭氧体积分数升高,EDU对叶片气体交换参数的影响显著,而对其他参数的影响不明显。由此可见,尽管EDU的防护作用对高体积分数的O3胁迫是有限的,但喷施EDU仍能有效减轻O3对植物的伤害,这对缓解农田生态系统O3污染灾害有积极意义。     

沙芥幼苗叶片解剖结构和光合作用对干旱胁迫的响应

为了了解干旱胁迫对植物光合作用和叶片结构的影响,明确植物光合作用和结构对干旱胁迫的响应,本研究以沙生植物、中国特有种---沙芥为材料,采用Li-6400光合仪和常规石蜡切片法,研究了干旱胁迫下沙芥光合参数、叶片解剖结构的变化,结合前期对沙芥叶片内活性氧物质含量变化的研究,试图阐述沙芥叶片应对干旱胁迫的机制,揭示沙生植物—沙芥在干旱环境中的生存策略,为植物耐旱性提供理论依据。结果表明：随着土壤含水量下降,净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)、叶片厚度、上表皮厚度、下表皮厚度呈下降趋势;海绵组织厚度呈先下降后上升的趋势;胞间二氧化碳浓度(Ci)呈上升的趋势;气孔限制值(Ls)、水分利用率(WUE)、栅栏组织和栅栏组织/海绵组织和叶片组织结构紧密度(CTR)呈先先上升后下降的趋势;且在土壤含水量大于39% WHC时沙芥光合和结构受影响较小,在土壤含水量低于39% WHC时,沙芥光合作用受到抑制,而叶片紧密度变大,能够较好的抵御干旱环境。结果表明干旱胁迫下沙芥幼苗叶片光合作用的下降是非气孔因素造成的,且其叶片结构的变化会影响光合作用,光合作用通过产生活性氧对结构也有影响。说明沙芥能够很好的适应中度干旱以上的环境,在重度干旱环境中沙芥通过调节叶片结构以适应环境,这可能是沙芥能够在沙漠地区生存繁殖的原因之一。     

Population genetic structure of the prosobranch Nassarius reticulatus (L.) in a ria seascape (NW Iberian Peninsula) as revealed by RAPD analysis

Randomly amplified polymorphic DNA (RAPD) banding patterns were compared between samples of the netted dogwhelk Nassarius reticulatus from 11 locations along the NW Iberian Peninsula coast. To detect if rias (estuaries formed by drowned river valleys) might promote genetic differentiation, five sampling sites were located within a ria (ria of Muros) and the remaining six were scattered along open-coast areas at increasing distances from the ria mouth. Population differentiation statistics (Φ-values) were estimated using a hierarchical analysis of molecular variance (AMOVA) with samples sorted into two groups: open-coast and ria populations. Despite a high potential to disperse, AMOVA demonstrated a modest, statistically significant genetic heterogeneity among N. reticulatus populations. Most of the genetic structure resided in differences among open-coast populations; ria populations were genetically homogeneous. No obvious geographical pattern was detected for the pairwise genetic distances (non-metric multidimensional scaling; UPGMA tree; Mantel test). Unlike previous studies with other species at a variety of estuarine systems other than rias, there was no evidence that the ria of Muros may enhance the genetic divergence of N. reticulatus populations. This discrepancy is discussed in relation to the biological features of the species (high dispersal potential and a preference for mid-low estuarine habitat) and the strong hydrographic connectivity between ria and neighbouring off-shore waters.     

Infectivity and efficacy of Glomus aggregatum and growth response of Cajanus cajan (L.) Millsp. in flyash amended sterile soil

In the present investigation a pot culture experiment was conducted using sterile, phosphorus deficient soil to study the effect of flyash at 3 different concentrations (10g, 20g and 30g flyash/kg soil) on the infectivity and effectiveness of VAM fungus Glomus aggregatum in pigeonpea (Cajanus cajan (L.) Millsp.) cv Maruti. The flyash amendment in soil at all the 3 different concentrations was found to affect significantly the intensity of VAM fungal colonization inside the plant roots and also suppressed the formation of VAM fungal structure (vesicles and arbuscules) completely at higher concentration (30g flyash/kg soil). The response of the pigeonpea plants, as judged by their higher and dry weight, under the influence of flyash amendment in VAM fungus infested soils was found to be considerably less (though not significant enough) when compared to the control plants (without flyash) that have otherwise shown significant increase in growth over the plants without Glomus aggregatum inoculation. However, flyash amendment without VAM inoculation was also found to enhance the growth of plants as compared to control plants (without flyash and VAM inoculum).     

Influence of destructive bacteria and red clover (trifolium pratense L.) on the pesticides degradation in the soil

Environmental Geochemistry and Health - Lindane and DDT (1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane) are pesticides from the group of persistent organic pollutants. These compounds, due to...