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1.
The open-air site la Rouquette, located at the foot of a cliff, was excavated by André Tavoso (1979-1988). The seven Mousterian archaeological levels are all in place, but of different richness. The sedimentological and faunal studies define a series of dates between isotopic stages 4 and 3, maybe even at the end of stage 5 for the lowest levels. The industrial complexes represent three broad types of “Bordian” facies, with technological, typological and lithological evolution. The industries from levels E to B display interesting evolutionary traits in so far as technological and typological behaviour are concerned, in a general Charentian Quina type Mousterian from the south of France continuum. After a “classical” facies in the “western” sense of the term (levels E to C), an atypical form of this facies (levels Bb and B) displays characteristics generally marked in the Quina Mousterian of the Grands Causses in more eastern or Mediterranean Quina Mousterians. Level Bb presents a Mousterian facies with a Ferrassie tendency, characterizing a short-term occupation. Level A contains a Mousterian defined as “non classical denticulates”, in which typical Mousterian and Charentian Mousterian influences are clearly marked.  相似文献   

2.
Variation in fish assemblage structure was examined in different rivers of the Seine Basin. Factor analysis was used to identify similarities among samples and species, and to show ichtyological changes along an upstream-downstream gradient. Fish species richness was correlated with catchment area, distance from the source and number of individuals. Relationships between species richness and number of individuals in a sample were largely an artifact of sampling.Species richness increased with river size, reached a maximum in midsize rivers, then decreased in large rivers. This species richness pattern was consistent with the model of the River Continuum Concept. However, possible causes could include greater pollution effects in large rivers. Distribution of feeding guilds was related to river size. Species richness and proportion of omnivores and piscivores increased with river size, whereas species richness and proportion of invertivores declined downstream. These patterns suggest that trophic diversity of fish assemblages may be related to food availability.  相似文献   

3.
Free proline content, superoxide-dismutase activity, and lipid peroxidation were measured in sixteen Yugoslav and introduced genotypes of soybean. More tolerant genotypes with higher free proline content and high superoxide-dismutase activity, and low lipid peroxidation were chosen. The selected genotypes could be used in field production, as well as in breeding.  相似文献   

4.
通过环境扫描电镜结合X射线电子探针显微分析技术,对21种不同基因型水稻颖壳内、外表面以及糙米表面、糊粉层、近糊粉层和米中部Pb含量的测定结果表明,21种不同基因型稻米不同部位Pb含量的变化范围由大到小的顺序为:颖壳内表面>糊粉层>近糊粉层>糙米表面>颖壳外表面>米中部;不同基因型稻米之间对Pb的富集量存在遗传差异,这种差异体现在稻米的同一部位和不同部位之间Pb含量的差异上;不同基因型水稻米中部Pb含量与颖壳内表面、糊粉层、近糊粉层、糙米表面、颖壳外表面之间、水稻糊粉层Pb含量与颖壳内表面、近糊粉层、糙米表面、颖壳外表面、米中部之间以及颖壳内表面Pb含量与颖壳外表面、糊粉层、近糊粉层、糙米表面、米中部之间均存在极显著或显著的非线性关系。一方面反映出不同基因型稻米中部Pb的富集量均通过颖壳和糊粉层调控,即存在相同的调控机制;另一方面揭示了不同基因型稻米不同部位之间对Pb富集的相互调控能力存在差异,并且基因型间的这种差异存在非线性的变化规律。  相似文献   

5.
A study has been made of the radionuclide content of sediments from Ponsonby Tarn in Cumbria to examine the pattern of deposition of radiocaesium and actinides upon the catchment. Sediment cores obtained from the tarn in 1986 were dated by core correlation and compared with results obtained from a previous study in 1980 (Eakins & Cambray, 1985).Sediments from the tarn contained actinides derived mainly from discharges to atmosphere. The 1986 cores contain greater quantities of weapons fallout derived caesium than may be accounted for by direct atmospheric input but less attributable to the Chernobyl accident than expected. Diatom analysis together with increased sediment accumulation rates post 1980 suggest that complex patterns of sedimentation have contributed to the changes evident in the sediment.  相似文献   

6.
Characterization of tobamovirus isolates collected from pepper crops in South East France has revealed the existance of several strains belonging to different viruses of the group. The biological and serological properties of three isolates (Vi76, Adam and Eve), selected as representative strains, have been studied. They have been compared with TMV and ToMV strains already isolated in our region as well as with other reference strains of ToMV-D and TMV-U1. They were also compared with other tobamovirus strains P11, P8 and P14, from the Netherlands, and PMMV-W from Italy also isolated from pepper genotypes possessing the “L” gene for resistance to TMV and ToMV strains. According to biological and serological reactions, Vi76 is more related to ToMV than to TMV but it is not related to Adam and Eve which are more closely related to PMMV. On the basis of the interaction with the “L” gene for resistance in pepper genotypes we have found that the Adam and P8 strains belong to the P1-2 pathotype and the Eve and P14 strains to the P1-2-3 pathotype and all the 4 strains belong to the PMMV-W group. In France, there have been no reports of the isolation of the P11 strain which is distantly related to the Adam strain.  相似文献   

7.
The societal importance of renewable carbon-based commodities and energy carriers has elicited a particular interest for high performance phototrophic microorganisms. Selection of optimal strains is often based on direct comparison under laboratory conditions of maximal growth rate or additional valued features such as lipid content. Instead of reporting growth rate in culture, estimation of photosynthetic efficiency (quantum yield of PSII) by pulse-amplitude modulated (PAM) fluorimetry is an often applied alternative method. Here we compared the quantum yield of PSII and the photonic yield on biomass for the green alga Chlorella sorokiniana 211-8K and the cyanobacterium Synechocystis sp. PCC 6803. Our data demonstrate that the PAM technique inherently underestimates the photosynthetic efficiency of cyanobacteria by rendering a high F0 and a low FM, specifically after the commonly practiced dark pre-incubation before a yield measurement. Yet when comparing the calculated biomass yield on light in continuous culture experiments, we obtained nearly equal values for both species. Using mutants of Synechocystis sp. PCC 6803, we analyzed the factors that compromise its PAM-based quantum yield measurements. We will discuss the role of dark respiratory activity, fluorescence emission from the phycobilisomes, and the Mehler-like reaction. Based on the above observations we recommend that PAM measurements in cyanobacteria are interpreted only qualitatively.  相似文献   

8.
We isolated seven algologically and five bacteriologically pure cultures of toxin-producing cyanobacteria from Turgen gorge (Kazakhstan), Karlovy Vary (Czech Republic), and Shar-Nuur Lake, Bayan Ulgiiregion (Mongolia) springs. According to the Daphnia magna test, Desertifilum sp. and Nostoc sp. strains were the most toxic in the test of isolated strains (complete death of all test organisms was detected after 48 h). These strains possessed the highest inhibitory effect on proliferation of the HeLa cancer cell line. The Anabaena sp. 35 and Nostoc sp. 4 strains were also high toxic. Model strains Synechocystis PCC 6803 and Synechococcus elongates PCC 7942, as well as the strain isolated in the present work, Synechococcus sp. 55, were less toxic. Mass spectrometry made it possible to assign cyanobacterial toxins to cyclic depsipeptides. Two cyclic depsipeptides, micropeptin T and oscillapeptin, were detected in Desertifilum sp. extracts. Cryptophycin and small amounts of cyclic depsipeptide micropeptin SD were detected in Nostoc sp. extract.  相似文献   

9.
Six potato genotypes with different degrees of heat tolerancewere grown in pots at 38/25 'b0C maximum/minimum temperatureat 14 h daylength under natural light glasshouse conditions.Prior to sampling, the plants were given a 14 h dark period.Photosynthesis was measured at 28 'b0C and at a saturating lightintensity of more than 1200 µEm-2 s-1. During the optimumphotosynthetic period (09.00–12.30 h), the leaves of heat-tolerantpotato genotypes (DTO-28, Norchip, and Desiree) had 4–5times more soluble sugars (mainly sucrose) and higher sucrose-phosphatesynthase activity than the leaves of the heat-susceptible genotypes(Kufri Jyoti, Kufri Chandramukhi, and Kufri Muthu). However,starch accumulation in leaves of susceptible genotypes was abouttwice that in tolerant genotypes. All susceptible genotypesshowed a low rate of assimilate transport from leaves and ahigher shoot/root ratio which indicated that the shoot remainedthe predominant sink for photosynthate. Activities of amylaseand invertase in leaves were also higher in susceptible genotypes.It is suggested that the poor yield of heat-susceptible genotypesat high temperature and long day conditions is related to insufficientavailability of the transportable sugar, sucrose. Key words: Solarium tuberosum, carbon partitioning, heat stress  相似文献   

10.
The spatio-temporal distribution of benthic colonies of Microcystis aeruginosa in Grangent Reservoir (France) in 2000 was not homogeneous and appeared to be controlled by many external factors: lake depth, station morphometry, substratum and hydraulic regime (lacustrine or fluvial). A most important concentration of benthic colonies was found at deep sites with fine sediment or at sites where the sediment was rich in organic matter. In spite of a stable water level and a minimum flow during summer, the number of benthic colonies showed great variation in the lacustrine downstream part of the reservoir. These variations may be explained by the dynamics of planktonic cyanobacteria.  相似文献   

11.
小麦不同基因型材料花药培养中雄核发育的研究   总被引:4,自引:0,他引:4  
薛建平  张爱民 《植物学通报》2002,19(2):215-218,214
对小麦离体花药中花粉发育的调查表明 :难诱导材料花药在培养初期 ,花粉退化快 ,大量小孢子败育 ,多细胞 (核 )花粉出现晚、频率低 ;而易诱导材料花药培养初期 ,花粉退化相对延缓 ,多细胞 (核 )花粉出现早且频率高 ,这些内在的优势使得更多的小孢子有可能转向孢子体发育 ,从而获得较高的出愈率。  相似文献   

12.
The fish communities of 371 sites from 4 natural regions of the Seine River basin were studied. The sites were located from small to medium size rivers (catchment area : 5 to 3895 km2). We examined the differences between local communities according to river size (estimated by catchment area) and region. In the Seine River basin, fish communities follow a general organisation rule: total species richness increases with river size and importance of limnophilic species versus rheophilic ones increases from upstream to downstream. However, fish communities show differences of total species richness, species richness of reproductive groups and species composition between the four natural regions of the basin. Particularly, river size and regional organisation of environmental factors interact on species composition of communities and several regional patterns of longitudinal changes of fish communities are identified. The origin and range of regional differences of fish communities are discussed according to historical and environmental factors.  相似文献   

13.
Radionuclide dating of the recent sediments of Blelham Tarn   总被引:9,自引:0,他引:9  
Lake sediments of the last 1000 years provide a unique record of environmental changes. Methods of dating this record are reviewed and discussed. Sediments of the last 20 years, which are of particular biological significance because of their record of man-made changes in lakes (including enrichment and pollution) have been dated successfully by the distribution within them of the fallout product 137Cs, present in the atmosphere since 1954 and reaching a peak of supply in 1963. The structured pattern shown by the curve for 137Cs concentration in most sediments investigated indicates that faunal mixing of the surface muds does not destroy the vertical stratification of the sediment profile. Sediments up to 120 years old have been dated by a lead isotope technique, and the results of this proved consistent with both 137Cs dating and with palaeomagnetic dating where this was possible. Theoretical considerations of the application of radiocarbon dating to organic material of 18th and 19th century date are reviewed. Results of application of these radionuclide techniques to the sediments of a small lake, Blelham Tarn, near Windermere, are presented. Evidence from 137Cs and 210Pb dating of profiles from several different positions within the lake shows that the depth of the annual increment to the sediments varies by a factor of × 2 from place to place. The concentration within the sediment of chemical and biological variables shows no significant variation from one position to another; therefore calculated values for amounts of each variable included within unit area of the annual increment depend primarily on the thickness of this at the site chosen, and so cannot be directly related to the rates of supply of, for example, pollen grains or total organic matter, and so to rates of productivity. Results from nine 14C dates on material 400–1000 years old, when correlated with analyses for pollen and sediment composition, demonstrate the profound effects of agricultural practices in the catchment (assumed to be deforestation and ploughing) in disturbing the orderly transfer to lake sediments of material eroded from the catchment.  相似文献   

14.
This paper describes a distribution problem involving Agrypnetes crassicornis and Phryganea obsoleta (Trichoptera : Phryganeidae) in Malham Tarn, Yorkshire. The only suitable habitat for their larvae is the offshore vegetation, chiefly Chara delicatula, but owing to the specialized egglaying behaviour of this family and the absence of other sites, the eggs of Agrypnetes crassicornis are laid on the exposed rocky shoreline. The situation with Phryganea obsoleta differs in that the emergence of Potamogeton spp. provides new oviposition sites away from the shore. Investigations on both species however have provided further support for an hypothesis which postulates the importance of wind-induced water movements in rapidly dispersing newly hatched insect larvae to the favourable habitats in deep water.  相似文献   

15.
Tubes composed of butyl rubber have been placed in a small English lake in an area where the water is 11-12 m deep. Each tube, when fully distended, contains over 18 000 m3 of water. The tubes are anchored to the shore and lake bottom. A boat can be rowed into them over a specially strengthened portion ofthe margin. The first was installed and its water isolated from that in the lake by the end of July 1970 and the second tube at the beginning of October 1970. The installation, maintenance, and performance of the tubes are described; as are suggested improvements. The temperature regime in the tubes closely follows that in the lake. If the chemical conditions are favourable, the seasonal cycle of Melosira in a tube is similar to that n i the lake. Contamination of the water in the tubes by that in the lake is slight and has a negligible effect on chemical conditions within them. Water can be lost from the tubes under certain conditions. The reverse does not happen. The phytoplankton communities in the tubes are similar in quality to those ofthe lake, even after 2-5 years of separation. The evidence suggests that the tubes are suitable for investigations on certain factors determining the abundance and seasonal cycles of algae in lakes and for other limnological studies.  相似文献   

16.
盐胁迫下不同基因型番茄可溶性物质含量的变化   总被引:47,自引:0,他引:47  
以两种野生番茄秘鲁番茄(Lycopersicon peruvianum LAlll)、潘那利番茄(Lycopersicon pennellii LA716)和两种栽培番茄鲜丰98-7、交农1号为材料,用NaCl 150 mmol/L进行盐胁迫,测定及分析了植株体内Na 、K 、Ca2 等无机离子和某些有机溶质游离脯氨酸、可溶性糖的含量.结果表明,盐胁迫条件下,野生番茄在新叶中积累了大量的Na 等无机离子,而栽培番茄新叶内脯氨酸和可溶性糖的含量却显著提高,且它具有将吸收的Na 区域化到老叶中的能力.说明野生番茄和栽培番茄在可溶性物质的合成和积累能力上有明显差异,它们是通过不同代谢途径和机理来适应盐环境的.  相似文献   

17.
Between 1992 and 1996, 95 rabbits from the immediate locality of Malham Tarn, North Yorkshire, UK were examined for the presence of helminth parasites. All the examinations took place in late September or October. Three species of nematodes, Graphidium strigosum, Passalurus ambiguus and Trichostrongylus retortaeformis and two species of cestodes, Taenia pisiformis and Cittotaenia pectinata were identified. There were no associations between helminth species richness and year of sampling, host weight or sex. A logistic model was fitted to the prevalence data from these helminths as was an over-dispersed Poisson model to the worm burden data. Graphidium strigosum was the most frequently identified species with an average prevalence of 78%. The mean prevalence and intensity of Graphidium infection were significantly effected by sampling year. The lower than normal rainfall recorded at the Tarn during the years 1995 and 1996 may have be one reason for this pattern. The worm burden of G. strigosum was significantly positively associated with rabbit body weight. The intensity of infection with P. ambiguus was significantly higher in female rabbits. There was a significant non-linear relationship between P. ambiguus worm burden and rabbit weight (P = 0.002) with worm burdens being highest in the 1000 g to 1499 g weight cohort. Trichostrongylus retortaeformis was only identified in 1994 and male rabbits harboured significantly higher worm burdens than females (48 vs. 7, P = 0.022). Over the five years, the average Taenia pisiformis prevalence was 31% and there was a significant positive association between worm burden and rabbit weight (P = 0.001). Cittotaenia pectinata had a prevalence of 37% over the whole study period with no interactions between prevalence or intensity and body weight, year of sampling or rabbit sex. All five helminths showed an overdispersed distribution with k values less than 1.  相似文献   

18.
The roles of weather variability and sunspots in the occurrence of cyanobacteria blooms, were investigated using cyanobacteria cell data collected from the Fred Haigh Dam, Queensland, Australia. Time series generalized linear model and classification and regression tree (CART) model were used in the analysis. Data on notified cell numbers of cyanobacteria and weather variables over the periods 2001 and 2005 were provided by the Australian Department of Natural Resources and Water, and Australian Bureau of Meteorology, respectively. The results indicate that monthly minimum temperature (relative risk [RR]: 1.13, 95% confidence interval [CI]: 1.02–1.25) and rainfall (RR: 1.11; 95% CI: 1.03–1.20) had a positive association, but relative humidity (RR: 0.94; 95% CI: 0.91–0.98) and wind speed (RR: 0.90; 95% CI: 0.82–0.98) were negatively associated with the cyanobacterial numbers, after adjustment for seasonality and auto-correlation. The CART model showed that the cyanobacteria numbers were best described by an interaction between minimum temperature, relative humidity, and sunspot numbers. When minimum temperature exceeded 18°C and relative humidity was under 66%, the number of cyanobacterial cells rose by 2.15-fold. We conclude that weather variability and sunspot activity may affect cyanobacteria blooms in dams.  相似文献   

19.
The degradation of an organophosphorus pesticide, fenamiphos, by different species of five green algae and five cyanobacteria was studied. All the species tested were able to transform fenamiphos to its primary oxidation product, fenamiphos sulfoxide (FSO), while the majority of these cultures were able to hydrolyze FSO to fenamiphos sulfoxide phenol (FSOP). Fenamiphos sulfone phenol, FSOP, and FSO were detected in the culture extracts of these algae and cyanobacteria. This is the first report on the biodegradation of a toxic pesticide, fenamiphos, by cyanobacteria. The ability of these algae and cyanobacteria to detoxify fenamiphos can be gainfully used in bioremediation of this pesticide and its toxic metabolites.  相似文献   

20.
不同光合特性大豆叶的比较解剖研究   总被引:2,自引:0,他引:2  
本研究选取不同光合速率的品种‘黑农 2 6’(高产低光效 )、‘黑农 40’、‘黑农 41’(高产高光效 )为材料 ,于大豆开花后的不同生育时期 ,对大豆的功能叶片、叶柄解剖学进行了研究。结果表明 :(1 )不同类型大豆的叶肉结构有明显区别。叶片厚度依次为‘黑农 40’ >‘黑农 41’ >‘黑农 2 6’。各期的基本趋势是一致的。栅栏组织的厚度和层数与叶片的厚度趋势一致。 (2 )各品种栅栏组织中的叶绿体数目均多于海绵组织 ,且高光效类型多于低光效类型。局部观察不同品种间 ,叶绿体内的基粒和间质片层结构高光效的也明显优于低光效的品种。 (3 )气孔包含数量和大小两个因素 ,气孔大小基本一致 ,下表皮数量 >上表皮 ,高光效类型 >低光效类型。 (4)各品种主脉维管束中木质部的导管数目依次为‘黑农 41’ >‘黑农 40’ >‘黑农 2 6’。  相似文献   

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