共查询到20条相似文献，搜索用时 31 毫秒
1.
Wei Yin-xin 《中国海洋湖沼学报》1994,12(2):180-184
The morphology and reproduction cycles of a new species,Zygnemopsis hubeiensis Wei are described and illustrated for a culture homothallic strain collected from Wuhan, Hubei, China. The asexual reproduction
is by parthenospores, aplanospores and akinetes. The major events of the sexual cycle, including the genuflection of reproductive
cells, gametangial development, gamete formation, gamete fusion, zygote formation, zygospore development, and zygospore germination
are observed. 相似文献
2.
Effect of temperature and irradiance on the growth and reproduction of Enteromorpha prolifera J. Ag. （Chlorophycophyta, Chlorophyceae） 总被引：1，自引：0，他引：1
Effect of temperature and irradiance on growth and reproduction of Enteromorpha prolifera that bloomed offshore along the Qingdao coast in summer 2008, was studied. It was showed that E. prolifera propagated mainly asexually with specific growth rate (SGR) of 10.47 at 25°C/40 μmol m-2s-1. Under this condition, gametes with two flagellate formed and released in 5 days. At the beginning of the development, the unicell gamete divided into two cells with heteropolarity, and then the apical cell developed into thalli primordial cells, whereas the basal cell developed into rhizoid primordial cells. In 8-day culture, the monoplast gamete developed into juvenile germling of 240 μm in length. Unreleased gametes can develop directly within the alga body. E. prolifera could either reproduce through lateral branching or fragmenting except apomixis revealed by Microscopic observation. On aged tissue of E. prolifera, although the degraded pigments partially remained in faded algal filaments, numerous vegetative ceils could still divide actively in the algal tissues. 相似文献
3.
Effect of temperature and irradiance on growth and reproduction of Enteromorpha prolifera that bloomed offshore along the Qingdao coast in summer 2008, was studied. It was showed that E. prolifera propagated mainly asexually with specific growth rate （SGR） of 10.47 at 25℃/40 μmol m^-2s^-1. Under this condition, gametes with two flagellate formed and released in 5 days. At the beginning of the development, the unicell gamete divided into two cells with heteropolarity, and then the apical cell developed into thalli primordial cells, whereas the basal cell developed into rhizoid primordial cells. In 8-day culture, the monoplast gamete developed into juvenile germling of 240 μm in length. Unreleased gametes can develop directly within the alga body. E. prolifera could either reproduce through lateral branching or fragmenting except apomixis revealed by Microscopic observation. On aged tissue of E. prolifera, although the degraded pigments partially remained in faded algal filaments, numerous vegetative cells could still divide actively in the algal tissues. 相似文献
4.
Two strains H2-410 and H2-419 were obtained from the chemically mutated survivors of wild Haematococcus pluvialis 2 by using ethyl methanesulphonate (EMS). Strains H2-410 and H2-419 showed a fast cell growth with 13% and 20% increase in biomass compared to wild type, respectively. Then H2-419-4, a fast cell growth and high astaxanthin accumulation strain, was obtained by exposing the strain H2-419 to ultraviolet radiation (UV) further. The total biomass, the astaxanthin content per cell, astaxanthin production of H2-419-4 showed 68%, 28%, and 120% increase compared to wild H. pluvialis 2, respectively. HPLC (High Performance Liquid Chromatography) data showed also an obvious proportional variation of different carotenoid compositions in the extracts of H2-419-4 and the wild type, although no peak of carotenoids appeared or disappeared. Therefore, the main compositions in strain H2-419-4, like its wild one, were free of astaxanthin, monoester, and diester of astaxanthin. The asexual reproduction in survivors after exposed to UV was not synchronous, and different from the normal synchronous asexual reproduction as the mother cells were motile instead of non-motile. Interestingly, some survivors from UV irradiation produced many mini-spores (or gamete?), the spores moved away from the mother cell gradually 4 or 5 days later. This is quite similar to sexual reproduction described by Elliot in 1934. However, whether this was sexual reproduction remains questionable, as no mating process has been observed. 相似文献
5.
Shi Pengju Dong Shihang Zhang Huanjun Wang Peiliang Niu Zhuang Fang Yan 《中国海洋湖沼学报》2018,36(2):490-507
Journal of Oceanology and Limnology - Polybrominated diphenyl ethers (PBDEs) are ubiquitous global pollutants, which are known to have immune, development, reproduction, and endocrine toxicity in... 相似文献
6.
观察了双棘黄姑鱼卵巢发育的周年变化,结果表明,双棘黄姑鱼雌鱼性腺成熟系数(GSI)一年有两个峰值,分别出现在5月份(9.38%±0.32%)和10月份(7.56%±0.43%);HSI与GSI密切相关[R=0.76];卵巢发育水温在19～29℃范围,繁殖水温为24～28℃,在广东省饶平海区,双棘黄姑鱼繁殖时间在每年的5月和10月,属于春、秋二季产卵类型的鱼类。 相似文献
7.
张虎才 《中国地理科学(英文版)》1998,8(4):377-382
ＧｅｏｌｏｇｉｃａｌｒｅｃｏｒｄｓｒｅｖｅａｌｅｄｔｈａｔｔｈｅＨｏｌｏｃｅｎｅｅｎｖｉｒｏｎｍｅｎｔｓｈａｄｅｘｐｅｒｉｅｎｃｅｄｄｒａｓｔｉｃｃｈａｎｇｅｓ,ｗｈｉｃｈｗａｓｃｌｏｓｅｌｙｒｅｌａｔｅｄｔｏｈｕｍａｎｅｖｏｌｕｔｉｏｎａｎｄｆｉｎ... 相似文献
8.
9.
“人力资源是第一资源”。在社会主义市场经济条件下，只有通过市场实现人力资源向人力资本的转变，人力资源才能作为现实的生产力要素发挥作用。否则只是消耗资源的消费者，而且是生产力发展的压迫因素。教育是人力资源的再生产环节，决定着人力资源的供给结构。我国现阶段人力资源向人力资本转变过程中存在的困难，一个重要原因就是人力资源的供给结构与市场的需求不相适应。所以必须通过发展和改革教育，促进人力资源向人力资本的转变。 相似文献
10.
为了保护渔业生态环境和渔业资源,从2001-2003年对广西桂平东塔鱼类产卵场水体实施了连续调查监测,对该水域水质的时空变化趋势和质量状况进行了研究和综合评价。结果表明,东塔产卵场水体处于相对清洁至轻污染状态;总氮、总磷、锌是重点监测和控制的优先污染物。 相似文献
11.
Zhang Hucai 《中国地理科学(英文版)》1997,8(4):377-382
Chronology establishment and dating data analyses on lacustrine deposits in northeastern Sahara show that vast fresh lakes
existed over there between 9900–2400 a B. P. Especially, great continuous lakes developed and got their maximum extent during
the period from 9800 a B. P. to 6450 a B. P. From 6000 a B. P. to 3600 a B. P., the evolution of the lakes experienced a new
stage with a property of drastic fluctuations and a periodicity of 600 years, which was the response to the climatic environment
changes. On the aspect of the relation between natural environment and the human, the warm-humid period in the Holocene was
not only a very important time for human development and evolution, but also was a moment for human reproduction and division.
On the other hand, this warm-humid period was also a distinguished time to natural environment changes, the accumulation of
the strong weathered debris and fine materials formed the basements for the formation of the Sahara Desert.
Supported by the National Natural Science Foundation of China, German Research Foundation and Gansu Provincial Natural Science
Foundation. 相似文献
12.
13.
Observation of female gamete （Carpogonia） germination of Porphyra yezoensis and P. oligospermatangia
Several papers have reported that part or whole leafy thallus seemingly consisting of zygotospores can give rise to both blades and conchocelis in the same culture of Porphyra. Study on samples of wild and cultivated Porphyra yezoensis and P. oligospermatangia were conducted to clarify the origination of the young blades in the culture. It is confirmed that single cells on the blade of both species, which normally intermixed with zygotospores, germinated into young blades. TEM and SEM observation has shown that the single cells of Porphyra yezoensis had typical features of female gamete （carpogonia） but archeospore. Therefore, the female gametes are responsible in developing leafy thalli. 相似文献
14.
Comparative study on Chinese urban agglomeration districts 总被引：2，自引：1，他引：1
ＣＯＭＰＡＲＡＴＩＶＥＳＴＵＤＹＯＮＣＨＩＮＥＳＥＵＲＢＡＮＡＧＧＬＯＭＥＲＡＴＩＯＮＤＩＳＴＲＩＣＴＳＬｉＣｈｅｎｇｇｕ（李诚固）ＨｕａｎｇＹａｎｊｕｎ（黄岩君）ＵｒｂａｎａｎｄＥｎｖｉｒｏｎｍｅｎｔＳｃｉｅｎｃｅＳｃｈｏｌ,ＮｏｒｔｈｅａｓｔＮｏ... 相似文献
15.
The formation and development of urban agglomeration districts are the inevitable trend of modern urban evolution. Owing to
the differences of formation background, urbanized way and process of different cities in the world, the feature and formation
mechanism of urban agglomeration districts in the world present obvious spatial differences. The paper inquires into the structure
feature, formation mechanism and development trend of different kinds of Chinese urban agglomeration districts by studying
four big urban agglomeration districts: Jing-Jin-Tang (Beijing-Tianjin-Tangshan), the middle and south of Liaoning, Hu-Ning-Hang
(Shanghai-Nanjing-Hangzhou), and Zhujiang River delta. The paper wants to promote the formation and development of theory
and practice system of Chinese urban agglomeration districts. 相似文献
16.
Yong Yuan Jianwen Chen Yuxi Zhang Jie Liang Yinguo Zhang Penghui Zhang 《中国海洋大学学报(英文版)》2018,17(5):1075-1090
The South Yellow Sea Basin is the main body of the lower Yangtze area in which marine Mesozoic–Paleozoic strata are widely distributed.The latest geophysical data were used to overcome the limitation of previous poor-quality deep data.Meanwhile,the geological characteristics of hydrocarbon reservoirs in the marine Mesozoic–Paleozoic strata in the South Yellow Sea Basin were analyzed by comparing the source rocks and the reservoir and utilizing drilling and outcrop data.It is believed that the South Yellow Sea Basin roughly underwent six evolutionary stages:plate spreading,plate convergence,stable platform development,foreland basin development,faulted basin development,and depression basin development.The South Yellow Sea Basin has characteristics of a composite platform-fault depression geological structure,with a half-graben geological structure and with a ‘sandwich structure' in the vertical direction.Four sets of hydrocarbon source rocks developed – the upper Permian Longtan–Dalong formation,the lower Permian Qixia formation,the lower Silurian Gaojiabian formation,and the lower Cambrian Hetang formation/Mufushan formation,giving the South Yellow Sea Basin relatively good hydrocarbon potential.The carbonate is the main reservoir rock type in the South Yellow Sea area,and there are four carbonate reservoir types:porous dolomitic,reef-bank,weathered crust,and fractured.There are reservoir-forming horizons similar to the typical hydrocarbon reservoirs in the Yangtze land area developed in the South Yellow Sea,and there are three sets of complete source-reservoir-cap rock assemblages developed in the marine strata,with very good hydrocarbon potential. 相似文献
17.
Sargassum muticum is one of the most abundant and conspicuous native macroalgae species on the northern coasts of China. It often forms large-scale seaweed beds in subtidal zones. This investigation was designed to understand the intraspecific genetic relationships of this alga based on samples collected from four northern coastal sites of China, and to evaluate gamete release and growth capacity in laboratory conditions. The nuclear internal transcribed spacer 2 （ITS2） sequences of 16 samples from four locations were identical. Based on cox3 gene and partial rbcLS operon sequences, intraspecific genetic variability was detected with three and two ribotypes, respectively. Temperature, not irradiance, was shown to significantly affect gamete release and fertilization. Elevated temperature and irradiance enhanced the growth of germlings and vegetative branchlets. Maximum growth rate of germlings was detected at 18-24℃and an irradiance of 60-100 μmol photons/（m^2.s）. Under ambient conditions （12-25℃ and 60-125 gmol photons/ （m2.s））, relative growth rate of young branchlets could reach 7.5%/d. 相似文献
18.
Sexual reproduction adversely affects the population growth of cyclic parthenogenetic animals. The density-dependent sexual reproduction of a superior competitor could mediate the coexistence. However,the cost of sex may make the inferior competitor more vulnerable. To investigate the effect of sexual reproduction on the inferior competitor,we experimentally paired the competition of one Brachionus angularis clone against three B rachionus calyciflorus clones. One of the B. calyciflorus clones showed a low propensity for sexual reproduction,while the other two showed high propensities. The results show that all B. calyciflorus clones were excluded in the competition for resources at low food level. The increased food level promoted the competition persistence,but the clones did not show a clear pattern. Both the cumulative population density and resting egg production increased with the food level. The cumulative population density decreased with the mixis investment,while the resting egg production increased with the mixis investment. A trade-off between the population growth and sexual reproduction was observed in this research. The results indicate that although higher mixis investment resulted in a lower population density,it would not determinately accelerate the exclusion process of the inferior competitor. On the contrary,higher mixis investment promoted resting egg production before being excluded and thus promised a longterm benefit. In conclusion,our results suggest that mixis investment,to some extent,favored the excluded inferior competitor under fierce competition or some other adverse conditions. 相似文献
19.
刘红玉 《中国地理科学(英文版)》1998,8(3):281-288
Ｗｅｔｌａｎｄ,ｗｉｔｈｖｅｒｙｈｉｇｈｂｉｏｌｏｇｉｃａｌｐｒｏｄｕｃｔｉｖｉｔｙ,ｔｒｅｍｅｎｄｏｕｓｒｅｓｏｕｒｃｅｐｏｔｅｎｔｉａｌａｎｄｅｎｖｉｒｏｎｍｅｎｔｆｕｎｃｔｉｏｎ,ｉｓａｓｐｅｃｉａｌｅｃｏｓｙｓｔｅｍｉｎｔｈｅｅａｒｔｈａｎ... 相似文献
20.
Liu Hongyu 《中国地理科学(英文版)》1997,8(3):281-288
Wetland is a special ecological system in the earth, which can provide a good habitat for many wild animals. It is a reproduction
and overwintering area for many rare waterfowls, too. The northeast region, including Heilongjiang, Jilin, Liaoning provinces,
and the east of Inner Mongolia, is a district with the maximum areas and types of wetlands in China. It is the center of the
waterfowls reproduction in Northeast Asia and the necessary region moving to the south. The conservation of wetland and waterfowls
habitats in northeast China plays an important role in international waterfowls habitats conservation. The northeast weterfowls’
types, number and distribution specific features are studied in three aspects in the paper, so do the rare waterfowls. Existing
problems and the administration polices on waterfowls and their habitats conservation in the northeast are also discussed.
It shows that the conservation of wetland waterfowls habitats in northeast China is important. 相似文献