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1.
The role of ribulose 1,5-bisphosphate carboxylase-oxygenase (Rubisco) in the regulation of photosynthesis in the field was assessed by following changes in the amount and activity of Rubisco and in the amounts of chlorophyll and total nitrogen in a willow (Salix cv. Aquatica gigantea) canopy during two growing seasons. An additional aim of this study was to determine how nitrogen is partitioned in the canopy and whether Rubisco and chlorophyll serve as sources of nitrogen. During both growing seasons, the total activity and the amount of Rubisco were high in young, sun-exposed leaves and decreased as the leaves aged and became shaded. In 1985, the specific activity was low (on average 0.8 micromol mm(-1) mg(-1) Rubisco protein) compared with the values obtained in 1986 (on average 1.8 micromol min(-1) mg(-1) Rubisco protein). These differences in the specific activity of Rubisco between the two years might be associated with changes in partitioning of nitrogen. During the cool summer of 1985, about 20% of the total nitrogen was partitioned to Rubisco compared with about 13% during the warm summer of 1986. Rubisco comprised a high proportion (about 60%) of the total soluble protein throughout the 1985 growing season, whereas during the 1986 growing season, the proportion of Rubisco in the total soluble protein fraction was lower and decreased markedly as the leaves became shaded. Chlorophyll did not serve as a source of nitrogen in the canopy. On the contrary, the proportion of total nitrogen in chlorophyll increased with time, which indicates acclimation of the thylakoid membranes to decreasing irradiance. The degree of activation of Rubisco in samples collected in 1986 was high in young, sun-exposed leaves, which suggests that in these leaves, Rubisco may limit the rate of CO(2) uptake. In the shaded leaves of the lower canopy, the degree of activation of Rubisco was low, which indicates that in these leaves, photosynthesis is limited by factors other than Rubisco. 相似文献
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山羊传染性胸膜肺炎支原体和绵羊肺炎支原体对抗菌药物敏感性的研究 总被引：4，自引：0，他引：4
测定了环丙沙星、氧氟沙星、单诺沙星、红霉素、罗红霉素、泰乐菌素、泰妙菌素、四环素等8种药物对羊肺炎支原体两个标准株Y-98和Y-goat的体外抑菌浓度以及红霉素与氧氟沙星、泰乐菌素对Y-goat和四环素与氧氟沙星、泰乐菌素对Y-98的联合药敏作用.结果表明,这8种抗菌药物对Y-goat和Y-98的MIC(μg/mL)分别为:环丙沙星0.223、0.002 23,氧氟沙星0.281、0.014 0,单诺沙星0.136、0.014 0,红霉素0.021 8、无效,罗红霉素0.032 7、无效,泰乐菌素0.042 2、0.039 0,泰妙菌素0.021 7、0.052 0,四环素0.195、0.052 0.红霉素与氧氟沙星的联合药敏指数为1,是相加作用;红霉素与泰乐菌素对Y-goat的联合药敏指数为1.5,是无关作用;四环素与氧氟沙星、泰乐菌素对Y-98的联合药敏试验指数均为0.375,是协同作用. 相似文献
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In vitro studies of Norwegian Red bovine semen immobilized and cryopreserved in alginate solid gel network 
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下载免费PDF全文 AH Alm‐Kristiansen ER Gaustad G Bai FB Standerholen G Klinkenberg E Kommisrud KE Waterhouse 《Reproduction in domestic animals》2018,53(2):365-370
Development of new semen cryopreservation techniques improving sperm survival and ensuring availability of viable spermatozoa for a prolonged time‐period after AI is promising tools to reduce sensitivity of timing of AI and enhance overall fertility. The SpermVital® technology utilizes immobilization of bull spermatozoa in a solid network of alginate gel prior to freezing, which will provide a gradual release of spermatozoa after AI. The objective of this study was to compare post‐thaw sperm quality and in vitro sperm survival over time of Norwegian Red bull semen processed by the SpermVital® (SV) technology, the first commercialized production line of SpermVital® (C) and by conventional procedure applying Biladyl® extender (B). Post‐thaw sperm motility was not significantly different between SV, C and B semen (p > .05). However, sperm viability and acrosome intactness were higher for SV than C and B semen (p < .05). Small differences in DNA quality were observed (p < .05). Sperm viability after storage in uterus ex vivo was higher for SV than for C semen (p < .05). Furthermore, sperm survival in vitro over time at physiological temperature was significantly higher for SV semen than C semen as well as B semen during the incubation period of 48 hr (p < .05). In conclusion, the SpermVital® technology is improved and is more efficient in conserving post‐thaw sperm quality and results in higher sperm viability over time in vitro for SV than for C and B semen. 相似文献
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Comparative Earth History and Late Permian Mass Extinction 总被引：6，自引：0，他引：6
The repeated association during the late Neoproterozoic Era of large carbon-isotopic excursions, continental glaciation, and stratigraphically anomalous carbonate precipitation provides a framework for interpreting the reprise of these conditions on the Late Permian Earth. A paleoceanographic model that was developed to explain these stratigraphically linked phenomena suggests that the overturn of anoxic deep oceans during the Late Permian introduced high concentrations of carbon dioxide into surficial environments. The predicted physiological and climatic consequences for marine and terrestrial organisms are in good accord with the observed timing and selectivity of Late Permian mass extinction. 相似文献
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Colin F Quinn John L Freeman Ray JB Reynolds Jennifer J Cappa Sirine C Fakra Matthew A Marcus Stormy D Lindblom Erin K Quinn Lindsay E Bennett Elizabeth AH Pilon-Smits 《BMC ecology》2010,10(1):19