Drought Tolerance Aspects in Pearl Millet

Different indices for selection of lines grown under low and high water levels were examined from both theoretical and practical standpoints. Pearl millet ( Pennisetum americanum (L.) K. Schum) was planted under a sprinkler irrigation gradient in 1983 and 1984. Equations were developed for drought tolerance for both yield and forage production. Correlation coefficients were developed for yield and yield components.
The equations showed that drought will generally result in decreased productivity of both grain and forage. Grain yield was found to be positively correlated with seed weight and with the number of seeds in the main head, and negatively correlated with plant height under low water level. Dry matter was positively correlated with tiller number.     

The Physiological Mechanism of Postphloem Sugar Transport in Citrus Fruit

The dynamics of translocation and partitioning of 14C-phothsynthates, the concentration of sucrose in fruit tissues and the effects of the membrane carrier- and ATPase-specific inhibitors on 14C-sucrose uptake by juice sacs of the satsuma mandarin (Citrus unshiu Marc. cv. Miyagawa wase) fruit were examined at the stage of fruit enlargement and fruit full ripe. Kinetic data of 14C-photosynthate translocation indicated that the rate of photosynthate transport into juice sacs decreased with fruit maturation and sugar accumulation. Along the photosynthate translocation path, i.e. from vascular bundles to segment epidermis then to juice sacs, a descending sugar gradient was observed. With fruit maturation and sugar accumulation in juice sacs, the 14C photosynthate gradient increased, whereas the static sucrose concentration gradient decreased with fruit maturation and sugar accumulation. The higher gradient of specific 14C radioactivity was considered to favor diffusion and sugar transport into juice sacs at the later stage of fruit development. The rate of uptake 14C-sucrose by juice sacs of satsuma mandarin fruit was markedly reduced by PCMBS, EB, DNP and NO-3 treatment. The above results suggested the participation of a carrier-mediated, energy-dependent sugar active transport process in juice sacs of satsuma mandarin fruit.     

农村人口梯度转移的动因与对策——以重庆市为例

以重庆市为例,从社会体制因素、产业发展因素、城镇规划因素、生活成本因素等方面分析了农村人口梯度转移的动因及合理性,并提出了4个方面的政策建议,即推进城镇建设、加大农村地区投资、促进劳动力市场建设和充分发挥保障作用。     

Elution of antimicrobials from a cross‐linked dextran gel: In vivo Quantification

Reasons for performing study: Use of a novel, biodegradable, antimicrobial‐impregnated gel provides an alternative method of local treatment of infections in horses. Objectives: To determine in vivo elution of antimicrobial medications from antimicrobial‐impregnated cross‐linked dextran gel and to evaluate the effect on wound healing when implanted subcutaneously in horses. Methods: Amikacin‐, vancomycin‐ or amikacin/clindamycin‐impregnated gel was placed subcutaneously in 11 horses' necks, using 6 replicates with a 3 month washout between experiments. Capillary ultrafiltration probes for collection of interstitial fluid were placed 0 cm and 1.5 cm from the gel‐filled incisions. Samples were collected at 0, 4, 8 and 12 h, and on Days 1–10. Blood was collected on Days 0, 1 and 7. Amikacin and vancomycin samples were analysed via fluorescence polarisation immunoassay, and clindamycin samples via high‐performance liquid chromatography. Histology of biopsy samples was performed at the completion of the study. Differences in mean histomorphological scores between groups were assessed using Wilcoxon's signed ranks test. Results: Maximum antimicrobial concentrations were detected at 4 h (amikacin), and 8 h (vancomycin, and amikacin and clindamycin from the combination gel). Mean ± s.d. peak concentrations for amikacin, vancomycin, amikacin (amikacin/clindamycin) and clindamycin were 6133 ± 1461, 7286 ± 2769, 3948 ± 317 and 985 ± 960, respectively. Median number of days for which antimicrobial concentration remained above minimum inhibitory concentration for target microorganisms at implantation was ≥10 days for vancomycin, 9 days (± 1) for amikacin and 8 days (± 1) for clindamycin. Mean plasma amikacin and vancomycin concentrations were lower than detectable limits; mean serum clindamycin concentrations were 0.52 µg/ml and 0.63 µg/ml at 24 h and 7 days, respectively. There were no significant differences in histomorphological scores between treatment and control incisions (P≥0.22). Conclusions and potential relevance: Cross‐linked dextran gel is a safe, effective alternative local antimicrobial delivery method.     

SOIL NITROGEN MINERALIZATION UNDER NORTHERN HARDWOOD FORESTS ALONG A SULFATE AND NITRATE DEPOSITION GRADIENT IN THE GREAT LAKES REGION

INTRODUCTIoNChangesinsoilNmineralizationratescouIdbeanearlywarningofsoilNavaila-bilityoreventualforestdeclinesinceNisoftenan.importantnutrientforgrowth(Keeneyl98O;Leaetal.l982;Vitouseketal-l982).Nitrogenmineralizationinvolvestwodistinctprocessesfammonification,inwhichNH:isformedfromorganiccom-pounds,andnitrification,theoxidationofNH:toNO3.ManystudiesofatmosphericdepositionimpactsonforestshavetargetedsoilNmineraIizationusingsimulatedaciddepositionundercontrolledlaboratoryconditions(T…     

基于改进的CTGC系统下不同CO2浓度对水稻生长发育的影响

为探索二氧化碳肥效作用对作物生长发育产量形成的长期影响及其在气候变化背景下的综合影响，验证改进后二氧化碳与温度梯度系统（CTGC）的精确性与可靠性，开展了水稻全生育期二氧化碳和温度梯度处理试验，测定了水稻生长发育及产量形成的反应，分析了环境因素对水稻生长发育的影响，并就试验系统原理和功能的改进做了说明。研究表明，处理小区水稻的籽粒灌浆增长和灌浆速率、干物质增长和增长速率显著增加，产量和生物产量显著增加，并且表现为随二氧化碳浓度与温度增高而增加的趋势。生物量增加尤以营养生长中后期旺盛表现最为明显，并使得水稻发育期略显延迟；处理小区水稻的经济系数比对照小区明显降低。表明二氧化碳与温度处理增加了水稻的生物量，二氧化碳肥效作用对水稻籽粒产量的提高具有潜力。     

柑橘完熟采收增糖效应及其机理

研究了完熟采收对宫川温州蜜柑果实精积累影响和光合产物在果实内的分配特性及运输机制。结果表明:完熟采收可使柑橘汁囊中葡萄糖、果糖、蔗糖含量明显提高。光合产物主要通过背维管束输入汁囊,完熟采收期间分配到汁囊的光合产物占整个果实18%,而分配到可食组织(维管束+囊瓣皮+汁囊)的光合产物却超过60%。从着色期到完熟采收期,维管束到囊瓣皮再到汁囊存在一个由高到低的~(14)C光合产物的放射性比活度梯度,其中从囊瓣皮到汁囊的梯度都随汁囊糖积累而稳步上升。上述结果表明完熟采收有利于提高果实含糖量,光合产物通过存在于运输路径中由高到低的光合产物梯度推动而持续输入汁囊是完熟采收增糖的主要原因。     

Influences of upland and riparian land use patterns on stream biotic integrity

We explored land use, fish assemblage structure, and stream habitat associations in 20 catchments in Opequon Creek watershed, West Virginia. The purpose was to determine the relative importance of urban and agriculture land use on stream biotic integrity, and to evaluate the spatial scale (i.e., whole-catchment vs riparian buffer) at which land use effects were most pronounced. We found that index of biological integrity (IBI) scores were strongly associated with extent of urban land use in individual catchments. Sites that received ratings of poor or very poor based on IBI scores had > 7% of urban land use in their respective catchments. Habitat correlations suggested that urban land use disrupted flow regime, reduced water quality, and altered stream channels. In contrast, we found no meaningful relationship between agricultural land use and IBI at either whole-catchment or riparian scales despite strong correlations between percent agriculture and several important stream habitat measures, including nitrate concentrations, proportion of fine sediments in riffles, and the abundance of fish cover. We also found that variation in gradient (channel slope) influenced responses of fish assemblages to land use. Urban land use was more disruptive to biological integrity in catchments with steeper channel slopes. Based on comparisons of our results in the topographically diverse Opequon Creek watershed with results from watersheds in flatter terrains, we hypothesize that the potential for riparian forests to mitigate effects of deleterious land uses in upland portions of the watershed is inversely related to gradient.This revised version was published online in May 2005 with corrections to the Cover Date.     

A gradient analysis of urban landscape pattern: a case study from the Phoenix metropolitan region,Arizona, USA

Landscape Ecology - Urbanization is arguably the most dramatic form of land transformation that profoundly influences biological diversity and human life. Quantifying landscape pattern and its...     

不同土壤颗粒组成在水蚀过程中的流失规律

研究结果表明，土壤有机质和全氮与〈１０μｍ土壤颗粒相关系数分别为０．６３１４和０．６７５０，与〈１μｍ粘粒的相关系数分别达到０．７２５４和０．７３２９；有机质和全氮在泥沙中的富集现象主要由侵蚀泥沙〈１μｍ粘粒富集造成；坡度与侵蚀泥沙粘粒、有机质和全氮的富集率的相关系数分别为－０．９８３２、－０．９３９５和－０．８１４６。