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The physical stresses associated with emersion have long been considered major factors determining the vertical zonation of intertidal seaweeds.We examined Porphyra umbilicalis(Linnaeus) Kützing thalli from the vertical extremes in elevation of an intertidal population(i.e.upper and lower intertidal zones) to determine whether Porphyra thalli acclimate to different vertical elevations on the shore with different patterns of nitrate uptake and nitrate reductase(NR) and glutamine synthetase(GS) activities in response to different degrees of emersion stress.We found that the nitrate uptake and NR recovery in the emersed tissues took longer in lower intertidal sub-population than in upper intertidal sub-population;and GS activity was also significantly affected by emersion and,interestingly,such an activity was enhanced by emersion of thalli from both upper and lower intertidal zones.These results suggested that intra-population variability in post-emersion recovery of physiological functions such as nutrient uptake and NR activity enables local adaptation and contributes to the wide vertical distribution of P.umbilicalis.The high GS activity during periodic emersion stress may be a protective mechanism enabling P.umbilicalis to assimilate nitrogen quickly when it again becomes available,and may also be an evidence of photorespiration during emersion. 相似文献
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鄱阳湖湿地水位与洲滩淹露模型构建 总被引：5，自引：1，他引：4
水是控制湿地生态过程的一个重要因子,为了研究洲滩变化和湿地草洲生长发育规律,以便更好地监测和保护湿地生态系统,有必要研究鄱阳湖水体变化特征,分析湿地洲滩水位的时空动态变化和洲滩淹露规律。本文以鄱阳湖国家级自然保护区为例,在对鄱阳湖多年水位进行分析的基础上,利用多时相遥感影像和DEM提取湿地洲滩特征;并在GIS支持下综合考虑地形、鄱阳湖水位、湖泊缓冲区等因素,建立了湿地水位及洲滩淹露模型。时空验证结果表明,该模型具有较好的模拟效果,精度在85%以上。同时,本文根据研究区特点及水体在TM2、7波段的特征差异,构建了一个新的水体指数FDWI,提取水体精度达到98%,特别是对潮湿的沙地、植被和云有很好的区分能力。 相似文献
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The effects of emersing oysters (Crassostrea gigas) for up to 66 h at 4 °C under humid air and nitrogen atmospheres were studied. A significant, gradual body mass loss occurred under nitrogen (8.36 ± 0.85% final weight loss) but no significant loss occurred under humid air (4.92 ± 2.67% final weight loss). Emersion duration and the mantle cavity fluid (MCF) total ammonia (TA) concentration showed a positive, linear relationship (r2 = 0.73 and 0.74 under humid air and N2, respectively). The MCF TA and trimethylamine (TMA) contents were also positively related (r2 = 0.64 and 0.69 under humid air and N2, respectively). 相似文献
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干出状态下羊栖菜的光合作用特性 总被引：6，自引：1，他引：5
生长于低潮带的海藻羊栖菜(Hizikia fusiformis)在低潮时常处于干出状态。羊栖菜在千出状态下可进行有效的光合CO2同化作用,虽然光合活竹比在海水状态时小。在于出状态下羊栖菜藻体发生脱水作用,在脱水15％以内时,光合活性没有显著变化,但随着进一步的脱水,光合活性急剧下降。在脱水率为38％时,光合活性下降至初始干出时的一半。现有大气中CO2浓度不能饱和羊栖菜在干出状态下的光合作用,H这种CO2限制随着藻体的严重脱水而加剧,其CO2羧化效率也随严重的脱水而急剧下降。减少脱水的因素(如海浪、藻体相互重叠等)以及大气CO2浓度升高有利于促进羊柄菜在干出状态下的光合作用。 相似文献
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为实现对建筑文物的“原真性”修复,利用X 射线衍射仪和激光粒度分布仪测定了历史建筑物中原胶凝材料矿物的组成和结构,并采用湿化学方法对原勾缝剂进行物料组成的复原,证明历史勾缝剂材料主要为石灰基材料。在复原的原胶凝剂材料配方的基础上分别加入活性火山灰、木质纤维素、分散性胶粉、早强剂和减水剂等对勾缝剂进行性能改进。经反复试验优选出了修复用勾缝剂材料的配方,并测试了试样的各项物理性能。结果表明,修复材料抗压强度达14. 47 MPa,饱和吸水率为 27. 07%,体积变化率＜ 1%,冻融循环4 次不变,证明改性后勾缝剂材料可以满足修复胶凝材料的性能要求。 相似文献
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