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排序方式: 共有151条查询结果,搜索用时 15 毫秒
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把鹧鸪菜藻体切成大小不同的切段、以及任意切碎,培养于添加氮、磷素的消毒海水中,后者分10℃、15℃、20℃、25℃四种不同温度条件培养,结果全部切段、切碎片都很快再生出假根附着于基质,并再生出一至多个叶状体;叶状体长大后从基部长出新的假根成为完整的幼苗(再生苗)。试验表明,大的切段其再生苗生长快、长度大,但出苗率(一定长度的藻体长出再生苗数量)低。培养温度较高时(20—25℃),藻体任意切碎片再生速度快、附着速度快、数量多且较牢固。利用藻体切碎片来培养鹧鸪菜幼苗是可行的;培养的适宜温度为20℃以上、海水比重为1.010左右。本文还对鹧鸪菜损伤藻体再生的情况(繁殖生殖学)进行一些观察和描述。 相似文献
3.
Spatio-temporal variability of small copepods (especially Oithona plumifera) in shallow nearshore waters off the south coast of South Africa 总被引:1,自引:0,他引:1
Francesca Porri Christopher D. McQuaid William P. Froneman 《Estuarine, Coastal and Shelf Science》2007,72(4):711-720
Although small copepods are one of the main dietary sources for many commercially important fish, their role in the pelagic trophic dynamics has traditionally been underestimated due to the methodology commonly used in plankton sampling. Temporal variation in abundance of adults and nauplii of small copepods (particularly Oithona plumifera) in nearshore waters on the south coast of South Africa was investigated fortnightly over 14 months at site (km) and location (100 m) scales. Sampling was within <500 m of the shore, where depth was ca. 10 m, using vertical hauls of an 80-μm mesh plankton net from 1 m above the seabed to the surface. Twenty-seven adult copepod taxa were recorded, but Oithona spp. was consistently the most abundant. Taxon richness was 7–19 on each sampling occasion. There was strong temporal variation (Oithona varied between 0 and 2300 m−3), but much of this was short-term variability (e.g. between consecutive sampling sessions), with no seasonality or other long-term discernable patterns. There were periods of consistently low numbers, but very high numbers often followed samples with low abundances. Nor was there spatial structure at the location scale, though numbers differed between sites. Despite considerable variability at the location scale within sites, Kenton consistently showed higher densities than High Rocks. Separate analyses, with Bonferroni adjustment, showed that this difference was significant on eight out of 21 occasions for Oithona, six for other pelagic copepods and three for nauplii. This suggests that hydrodynamics favour aggregation of plankton at Kenton. A high degree of short-term variability, with a tendency for aggregation of small zooplankton at certain sites has implications for both pelagic processes and food-web links between the benthic and pelagic environments. 相似文献
4.
Long-term changes in ray populations in the North Sea 总被引:2,自引:3,他引:2
5.
Katherine M. Papastephanou Stephen M. Bollens Anne M. Slaughter 《Deep Sea Research Part II: Topical Studies in Oceanography》2006,53(25-26):3078
Cross-shelf distribution and abundance of copepod nauplii and copepodids were measured during three summer upwelling seasons (2000–2002) in a coastal upwelling zone off northern California. These 3 years varied considerably in the intensity of winds, abundance of chlorophyll, and water temperature. The cruises in 2000 were characterized by relaxation conditions, with generally high levels of chlorophyll and high water temperature. The cruises in 2001 and 2002 were dominated by strong and persistent upwelling events, leading to lower chlorophyll and water temperatures. The copepod assemblage was dominated by Oithona spp., Acartia spp. and Pseudocalanus spp., with Metridia pacifica (lucens), Microsetella rosea, Oncaea spp. and Tortanus discaudatus also common during all 3 years. The cross-shelf distribution of copepods was generally shifted offshore during upwelling and onshore during relaxation events, although some variability between species occurred. Abundance of all life stages generally exhibited a negative correlation with cross-shelf transport averaged over at least 1–4 days and lagged by 0–3 days, indicating lower abundances during and immediately after active upwelling. However, copepod nauplii seemed to respond positively to wind events lasting 1–5 days followed by a period of relaxation lasting 6 or 7 days. These rapid rates of change in abundance are probably too great to be due to in situ growth and reproduction alone; physical processes must also play a role. These results suggest a highly dynamic relationship between copepods and upwelling events off northern California, with species-specific responses to upwelling to be expected. 相似文献
6.
鳗鲡气单胞菌引起的烂尾病病原菌抑菌药物的研究 总被引:5,自引:0,他引:5
应用药敏纸片法研究了三株烂尾病病原菌(气单胞菌)对31种药物及不同配合药物的敏感性,测定了4种药物及配合药物HP对三株菌的最低抑菌浓度(MIC)及最低杀菌浓度(MBC)。结果表明,配合药物HP具较强的抑菌能力。 相似文献
7.
Stem wood of the Angiosperm Calluna vulgaris (Scotch heather), isolated at different depths from a selection of raised bog peat deposits, was chemically characterized using in-source pyrolysis mass spectrometry (Py-MS) and Curie-point pyrolysis gas chromatography mass spectrometry (Py-GC-MS). Light microscopy was performed to relate mass spectrometric characteristics with anatomical features. Peatified wood samples, isolated from increasing depth show a gradual decrease in carbohydrate content. This decrease in anatomically reflected in a selective removal of secondary cell wall material from the fibre-tracheids and wood parenchyma. During prolonged peatification a selective removal of hemicellulose sugars is observed, while a part of the cellulose fraction is preserved. This highly resistant cellulose is mainly located in the secondary cell walls of the vessels. The lignin macromolecule is preserved, but a gradual decrease in syringyl to guaiacyl ratio (S/G) is observed during peatification. Because no increase in catechol and phenolic compounds is observed, we conclude that S/G shifts are due to removal the of syringyl-rich secondary cell wall material and the retention of guaiacyl-rich compound middle lamella. Small chemical changes in the lignin macromolecule involve shifts in oxygen substitutions on the aliphatic side chains of the methoxyphenolics and the occurrence of aromatic acids. 相似文献
8.
研究了不同浓度Hg2 +对水鳖叶片光合放氧速率、呼吸速率、细胞膜透性、硝酸还原酶活性以及超微结构的毒害影响 .结果表明 ,随着Hg2 +浓度的增加 ,水鳖叶片的光合放氧速率逐渐下降 ,呼吸速率、硝酸还原酶活性先升后降 ,而细胞膜透性则逐渐上升 .电镜观察发现 ,水鳖叶细胞遭受Hg2 +毒害初期 ,染色质凝集 ,叶绿体中类囊体片层以及线粒体嵴突膨胀 .随着叶细胞遭受毒害程度的加深 ,核膜破裂 ,染色质与核质消失 ,叶绿体膨胀解体 ,线粒体空泡化 相似文献
9.
Wang Wenli Institute of Natural History Beijing Natural History Museum Yang Zunyi 《《地质学报》英文版》1993,67(3)
A new insect family Liaoximordellidae (fam. nov.) has been named for a well-preserved specimen which was collected from the Upper Jurassic outcropping west of Daxinfangzi Village, Lingyuan County, Liaoning Province. The specimen can not be put into Mordellidae or Praemordellidae because it possesses some original and intermediate characters in morphology. It serves the study of mordellid evolution. Besides, the fossil group associated with the insect is important for the stratigraphic division of the Mesozoic in western Liaoning. 相似文献
10.
对点带石斑鱼【Epinethelus malabaricus(Block et Schreider)】烂尾病进行了病理组织学观察。结果表明:烂尾病的病因是病原菌侵袭病鱼,而产生一系列的炎症反应,在病原菌的影响下,病鱼的尾柄部鳞片松脱,皮肤裸露、溃烂,最后鳍条脱落,鳃、肝脏、肾脏、心脏、肠等器官均有不同程度的病变。还对烂尾病产生的原因和病变过程进行了探讨,并提出控制烂尾病发生的一些途径。 相似文献