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971.
Gengmei?Xing Jun?Zhang Jing?Liu Xiaoyan?Zhang Genxuan?WangEmail author Yafu?Wang 《Phytoparasitica》2003,31(5):499-514
The impacts of elevated CO2 and soil water on the population dynamics, adult fecundity and nymphal period of the bird cherry-oat aphidRhopalsiphum padi (Linnaeus) were evaluated in three experiments: (i)Combined effects of CO
2
and soil water on aphid populations. Spring wheat was grown in pots at three CO2 concentrations (350, 550 and 700 ppm) and three soil water levels (40%, 60% and 80% of field water capacity, FWC) in field
open-top chambers (OTC) and infested with the bird cherry-oat aphid. Aphid population dynamics were recorded throughout the
growing season; at the same time, adult fecundity and duration of the nymphal period were recorded. Chemical composition of
spring wheat leaves was also analyzed. (ii)Indirect effects of CO
2
concentrations and soil water on aphid adult fecundity and nymphal period. The experiment was conducted with the leaf discs method in the laboratory. Aphids were reared on leaf discs excised from
the treated wheat in OTC with different CO2 and soil water levels. (iii)Direct effects of CO
2
concentrations on aphid adult fecundity and nymphal period. Aphids were reared on leaf discs excised from the wheat grown under natural conditions. The experiment was conducted with
the leaf disc method in OTC with the three CO2 concentrations. It was found that the direct effect of CO2 concentration on aphid population parameters was minor. CO2 and soil water affected aphid population indirectly through their effects on wheat characteristics. The aphid population
under 550 ppm CO2 was far larger than the one under 350 ppm CO2, whereas the population under 700 ppm CO2 was slightly higher than that under 550 ppm CO2. The largest aphid population was obtained with the 60% soil water treatment, regardless of CO2 treatment. The effects of CO2 concentration on aphid population were, however, not significantly correlated with soil water level. Adult fecundity increased
with CO2 concentration, the highest fecundity being achieved under 60% FWC treatments. The nymphal period was not affected by CO2 concentration. The shortest period occurred under 60% FWC. Atmospheric CO2 and soil water had significant effects on the chemical composition of the wheat leaves. Aphid population size was positively
correlated with leaf water content, concentrations of soluble proteins, soluble carbohydrates and starch, and negatively correlated
with DIMBOA and tannins concentrations.
http://www.phytoparasitica.org posting Oct. 20, 2003. 相似文献
972.
半干旱黄土丘陵区小流域横断面土壤水分生态特征 总被引:9,自引:0,他引:9
在半干旱地区甘肃榆中北部中连川流域取一横断面,根据地形部位与利用条件布设11个测点,用土钻法监测土壤水分剖面分布与动态,测深到5m。各立地条件年内4月到12月土壤水分动态趋势多样。流域横断面的土壤湿度均较低,2~5m平均值一般都小于10%,其中以坡地苜蓿与半阳坡柠条林地最干燥。该地区土壤干燥化层是普遍存在的,不仅存在于人工植被,也存在于天然植被。径流富集叠加可显著改善土壤水分状况,隔坡水平梯田是其重要途径。退耕还草中要考虑各类草地的比例、苜蓿种植的适宜规模及其持续性问题。 相似文献
973.
Although it is well known that judicious use of adjuvants can increase the performance of foliage-applied sprays of many agrochemicals, little information is available in the public domain about their ultimate effects on pesticide residues in treated crops. In the present work, the influence of Agral (polyoxyethylene nonylphenols), Toil (methyl esters of rapeseed fatty acids) and Bond (styrene-butadiene copolymers) on surface and crop residues of diclofop-methyl/diclofop and propiconazole in wheat and field beans was investigated using a model system simulating field practice. Pesticides were applied as commercial formulations, diclofop-methyl 378 g litre(-1) EC (Hoegrass) and propiconazole 250 g litre(-1) EC (Tilt), at their maximum approved rates, 1135 g AI ha(-1) and 125 g AI ha(-1), respectively, both in the presence or absence of the maximum rate recommended for each candidate adjuvant. No detectable residues of diclofop-methyl or propiconazole were found in wheat 35 days after any of the four applications. However, residues of diclofop were present in this crop, and those from applications containing Agral (0.07 mg kg(-1) fresh weight (FW)) or Bond (0.08 mg kg(-1) FW) were significantly lower than those with no adjuvant (0.14 mg kg(-1) FW) or Toil (0.16 mg kg(-1) FW). Unlike wheat, residues of both diclofop and propiconazole were detected in field beans after harvest. Significantly higher residues of the former were recorded from the applications with Agral or Bond (ca 0.32 mg kg(-1) FW) than with those with no adjuvant or Toil (ca 0.15mg kg(-1) FW). All the propiconazole applications containing adjuvants showed a similar significant increase in residues (0.10-0.16 mg AI kg(-1) FW) over the no-adjuvant treatment (0.05 mg kg(-1) FW) in this crop. There appeared to be little agreement between the apparent amounts of uptake, as indicated by the rates of decline of surface residues up to 5 days after application, and final residues in either target species. On wheat, surface residues of diclofop-methyl decreased from initially ca 20 to as little as 0.02 mg kg(-1) FW using adjuvants; the corresponding values for propiconazole were ca 2 to ca 0.03 mg kg(-1) FW. Recoveries of diclofop-methyl from the surfaces of field beans were much higher than those from wheat, declining from ca 30 to only ca 6 mg kg(-1) FW during the course of 5 days; the corresponding residues for propiconazole were ca 2 mg to 0.15 mg kg(-1) FW. These findings are discussed in relation to uptake results obtained with radiolabelled pesticides and adjuvants in the laboratory, and to the mandatory requirements for pesticide residue data for the authorised use of adjuvants in the UK. 相似文献
974.
Dissipation of dithiopyr in soil was monitored after application to wheat crop as pre- or post-emergence applications at two rates, viz 100 and 200 g AI ha(-1). The level of dithiopyr in the soil was assessed by gas chromatography, and its disappearence was found to follow a first-order decay curve irrespective of rate or method of application. The half-life in soil ranged between 17.3 and 25.0 days and residues at harvest (150 days after application) ranged between 4.0 and 8.8% of amounts applied. Investigation of microbial degradation of dithiopyr was conducted in minimal salt and Czapek Dox media in which 80% of the compound degraded within 15 days. Residues were not detected in wheat grain at harvest. 相似文献
975.
车晓勤 《安徽农业大学学报》2002,(4):97-99
二十世纪90年代,世界格局发生了根木的变化,人类试图在“全球一体化”的语境中寻求共同的利益。经济领域计划经济向市场经济的转型势必会引起上层建筑中文化、意识的转型。转型期的中国当代文学呈现出现代主义”与后现代主义”文化语境互相渗透,知识分子人文意识的变化与失落,文学创作的精神属性淡化与商品生产强化的特点。 相似文献
976.
Double in situ hybridization using a digoxigenin-labelled porcine circovirus 1 (PCV1) and biotinylated PCV2 probe, was developed for the simultaneous detection and differentiation of PCV1 and PCV2 in formalin-fixed, paraffin-embedded tissues from pigs with postweaning multisystemic wasting syndrome. The combination of an alkaline phosphatase conjugated antidigoxigenin system with alkaline phosphatase conjugated streptavidin-biotin system allowed identification of PCV1 and/or PCV2. No evidence of cross-reaction was observed. Positive cells exhibited a red or dark brown reaction product for PCV1 and PCV2, respectively. Both PCV DNAs were observed mainly in the cytoplasm but occasionally in the nucleus. Co-localization of hybridization signal for both PCV1 and PCV2 was present in macrophages and multinucleated giant cells of the lymph node and spleen. This double-labelling technique for the differentiation between PCV1 and PCV2 is suitable for pathogenesis studies and diagnostic applications. 相似文献
977.
Bush cover and range condition assessments in relation to landscape and grazing in southern Ethiopia 总被引:6,自引:0,他引:6
Progressive growth of bush cover in dry savannahs is responsible for declines in range conditions. In southern Ethiopia, the Booran pastoralists assisted our understanding of spatial patterns of bush cover and range conditions in 54 landscape patch types grouped into six landscape units within an area of 30000 km2. The size of landscape patches sampled was 625 m2. We assessed the relationships between bush cover, grass cover and bare soil and grazing pressure and soil erosion and changes in range condition. Externally, political conflicts and internally, break down of land use, and official bans on the use of fire promoted bush cover and the decline in range conditions. Bush cover was negatively correlated with grass cover, and positively correlated with bare soil. Grass cover was negatively correlated with bare soil and grazing pressure in most landscape patch types. Grazing pressure was not significantly correlated with bush cover or bare soil, while soil erosion was directly related to bare soil. Soil erosion was absent in 64% of the landscape patch types, and seemingly not a threat to the rangelands. The relationship between bush cover, grass cover, bare soil and soil erosion is complex and related to climate, landscape geology, and patterns of land use. Main threats to range conditions are bush climax, loss of grass cover and unpalatable forbs. Currently, >70% of the landscape patch types are in poor to fair range conditions. Decline in range conditions, unless reversed, will jeopardise the pastoral production system in southern Ethiopia. 相似文献
978.
979.
980.
一个山羊Ⅰ型毛角蛋白基因的序列及其在皮肤中的表达 总被引:7,自引:0,他引:7
角蛋白家族包含表皮软角蛋白和毛发硬角蛋白,可以分为酸性Ⅰ型和碱性或中性的Ⅱ型角蛋白亚家族。从构建的成年山羊皮肤cDNA文库和ESTs分析中发现了和与绵羊羊毛角蛋白8C1和人Ⅰ型毛发角蛋白相应cDNA序列高度同源的序列,经序列分析证明是一个山羊毛发特异性角蛋白,命名为山羊Ⅰ型毛角蛋白1(gHa1),Gen Bank序列号为AY510110.1。推导的读码框ORF由413氨基酸组成,与绵羊8C1角蛋白的序列一致性为97.8%。原位杂交显示它在皮肤初级和次级毛囊的皮质层有强烈的表达。 相似文献