Changes in root growth and relationships between plant organs and root hydraulic traits in American elm （Ulmus americana L.） and red oak （Quercus rubra L.） seedlings due to elevated CO2 level

The relationships between plant organs and root hydrological traits are not well known and the question arises whether elevated CO2 changes these relationships. This study attempted to answer this question. A pseudo-replicated experiment was conducted with two times 24 American elm(Ulmus americana L.) and 23 and 24 red oak(Quercus rubra L.) seedlings growing in ambient CO2(around 360 μmol·L-1) and 540 ± 7.95 μmol·L-1 CO2 in a greenhouse. After 71 days of treatment for American elm and 77 days for red oak,14...     

Genetic isolation by distance and landscape connectivity in the American marten (Martes americana)

Empirical studies of landscape connectivity are limited by the difficulty of directly measuring animal movement. ‘Indirect’ approaches involving genetic analyses provide a complementary tool to ‘direct’ methods such as capture–recapture or radio-tracking. Here the effect of landscape on dispersal was investigated in a forest-dwelling species, the American marten (Martes americana) using the genetic model of isolation by distance (IBD). This model assumes isotropic dispersal in a homogeneous environment and is characterized by increasing genetic differentiation among individuals separated by increasing geographic distances. The effect of landscape features on this genetic pattern was used to test for a departure from spatially homogeneous dispersal. This study was conducted on two populations in homogeneous vs. heterogeneous habitat in a harvested boreal forest in Ontario (Canada). A pattern of IBD was evidenced in the homogeneous landscape whereas no such pattern was found in the near-by harvested forest. To test whether landscape structure may be accountable for this difference, we used effective distances that take into account the effect of landscape features on marten movement instead of Euclidean distances in the model of isolation by distance. Effective distances computed using least-cost modeling were better correlated to genetic distances in both landscapes, thereby showing that the interaction between landscape features and dispersal in Martes americana may be detected through individual-based analyses of spatial genetic structure. However, the simplifying assumptions of genetic models and the low proportions in genetic differentiation explained by these models may limit their utility in quantifying the effect of landscape structure.     

美洲斑潜蝇的为害及生物学特性研究

研究表明，美洲斑潜蝇的寄主植物主要有茄科、豆科、葫芦科，其次有十字花科、菊科、锦葵科等。受害严重的作物，平均单叶有虫道１００．４个，单叶有幼虫４６．３头，被害叶率达８５．２％，有虫株率和被害株率均达１００％；研究还表明，美洲斑潜蝇从植株下部开始为害，且以植株中上部虫量最多，而被害叶位多逐叶上移；通过室内饲养和田间观察获知美洲斑潜蝇在茄子、西葫芦和地芸豆上各虫态的发育历期，并描述了其习性     

我国国家果树种质资源的研究现状及展望 —基于中美两国国家果树种质资源圃的比较

果树种质资源的保存及评价是果树品种选育的重要基础。本文通过对中美两国国家果树种质资源圃（库）在果树种质资源的收集、保存及评价等方面的比较分析,了解中美两国国家果树种质资源圃各自的发展进程及各自优缺点,为我国果树种质资源保存与评价提供重要参考依据,以期完善我国果树种质资源研究体系。同时结合我国果树种质资源的收集、保存及利用情况及存在的问题,提出了发展建议。     

西洋参果肉乙醚相中发芽抑制物质的研究

本文首次报道从西洋参果肉中分离鉴定４种发芽抑制物质－－乙酸、丁酸、异相酸和苯乙酮,同时利用标准品测定有效抑制浓度分别为１０、１０、１００和１００μｌ／Ｌ。从而明确西洋参种子成熟时,种胚尚不能成熟的主要原因之一是果肉中存在磋眵种抑制活性较强的发芽抑制物质。     

Re‐evaluating the population size of South American fur seals and conservation implications

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Lipid content and fatty acid composition in female American shad,Alosa sapidissima,at different stages of ovarian development under reared conditions

The fatty acid accumulation in broodstock influences the fecundity of spawners as well as egg quality. A comprehensive understanding of the lipid and fatty acid changes in broodstock during the reproductive period can increase our knowledge of the nutritional requirements in artificial breeding programs. The study assessed the lipid and fatty acid compositions of muscle, liver and ovary of American shad at different stages of reproductive development under reared conditions. The results indicated that there were significant differences in lipid content among ovary, liver and muscle. Mean total lipid levels in ovary, liver and muscle were 15.92%–10.87%, 13.62%–6.89%, 10.39%–6.11% respectively. During the development season, the total lipid content in muscle in stages V and VI were significantly lower than those in stages II and III. The total lipid content in liver in stages IV, V and VI was significantly lower than in stages II and III, whereas the total lipid content in the ovary increased significantly as the gonad developed and reached its highest value at stage V. From II to VI stage, the liver content of docosahexaenoic acid (DHA) decreased and the ovarian content of DHA increased, whereas the content of eicosapentaenoic acid (EPA) remained relatively constant. The content of C16:0 and C18:1n‐9 decreased in muscle and liver, but significantly increased in ovary. It is therefore suggested that the lipids were preferentially transferred from muscle and liver to ovary beginning in stage IV as the gonad matured. At stage IV, the lipid transfer accelerated, and saturated and unsaturated fatty acids, such as C16:0, C18:1n‐9, DHA, EPA and arachidonic acid, were selectively transferred to and conserved in ovaries.     

Dynamic changes in American lobster suitable habitat distribution on the Northeast U.S. Shelf linked to oceanographic conditions

American lobster (Homarus americanus) supports one of the most valuable regional fisheries in the United States, with its abundance and distribution profoundly influenced by environmental conditions. To explain how lobster distribution has changed over time and assess the role of environmental variables on these changes, we used random forest classification and regression tree models to estimate occupancy and biomass in two seasonal periods. The occupancy models were fit to static and dynamic variables, which yielded model fits with AUC scores of 0.80 and 0.78 for spring and fall, respectively. Biomass models were fit with the same data and resulted in models explaining 61% and 63% of the spring and fall biomass variance, respectively. Significant variables scored in the formation of the regression trees were secondary productivity (i.e., zooplankton), bathymetry characteristics, and temperature. American lobster suitable habitat has changed regionally; habitat has increased in the Gulf of Maine and declined in Southern New England. There is also evidence of declining habitat along the inshore margin of the Gulf of Maine, which has been accompanied by a shift in occupancy probability offshore. Habitat suitability results from the random forest models provide insights on the structure and function of lobster habitat and context to understand recent population trends.     

美国优良李品种湖北引种试验结果

李树花期受晚春低温阴雨冻害是限制李子商品化生产发展的主要问题。我所从美国奥本大学引进了27个优良李品种（系）,经过近10a的试验观察,结果表明：圣罗莎、欧扎克总理、奥本罗莎、奥本82－1,蜜斯李、紫李、奥本樱桃李等综合经济性状优良,适宜在湖北各地推广。     

不同加工类型原皮西洋参的电子显微分析

对不同加工类型的原皮西洋参进行隧道电镜扫描、分析,研究结果表明：冷冻干燥、真空干燥的产品内部结构良好，淀粉粒、树脂道、草酸钙晶体等微观结构清晰可辨；传统烘房干燥的正常参也具有良好的内部结构；但是，微波干燥、传统烘房干燥的不正常参．如褐变参、青枝等于制品．干燥过程中其内部结构已被破坏．产品的内外结构均不符合商品要求。因此，可以利用电镜显微分析对西洋参的干制品质量进行分析、判断，评价产品的优劣。