摘要 :
Three life-history stages including reproductive allocation (RA)，gametogenesis andrecruitment influence the population structure of Sargassum thunbergii． Based on thislife-history cycle，the reproductive ecology of the species w...
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Three life-history stages including reproductive allocation (RA)，gametogenesis andrecruitment influence the population structure of Sargassum thunbergii． Based on thislife-history cycle，the reproductive ecology of the species was researched．
Annual reproduction initiated in mid-June and peaked in mid-July (90% fertilethalli and 75% RA mean)． Both RA and percentage of fertile thalli exhibitedsignificant temporal variations during reproduction． Sterile thalli were only observedin small hierarchies at peak reproduction and mean values of RA showed asignificantly hierarchical variation，suggesting that the size of thalli played importantroles in reproduction and both reproduction and RA were size-dependent． Numerousreceptacles were produced along the lateral branches during the reproductive period．A distinct seasonal pattern was observed wherein the presence of lateral branches wasfollowed by the onset of reproduction． RA was positively correlated with the numberof lateral branches，as well as the total length of lateral branches，suggesting that theappearance of lateral branches is of importance for reproduction． In addition，massiveshedding of modules occurred after the reproductive season． Moreover，theprobability of shedding was evidently higher for fertile than for sterile modules，because all surviving thalli were sterile and short during July-August． So，a trade-offbetween reproduction and survival may exist at individual levels in S． thunbergii．
Much attentions have been paid to the gamete release of fucoid algae，but theinteractions between the environmental cues and their importance order for thegamete release remain little known． In this study，a 28-4 fractional factorial design(Resolution Ⅳ) was used to identify the main effects and interactions ofenvironmental factors of S． thunbergii． Of the factors tested，water motion，temperature，photoperiod and salinity were found to be the most important factorsaffecting egg release． Moreover，the interactions between any two factors were allsignificant． Based on the size of effect estimated by ANOVA，the effects whichcontribute to the release of eggs，in order of importance，are： salinity，watermotion*photoperiod (possibly temperature*salinity)，water motion*salinity (possiblytemperature*photoperiod)，temperature，water motion*temperature (photoperiod* salinity)，water motion and photoperiod． The optimum conditions of 25℃，30 psusalinity，slack seawater and 12 h irradiance that achieved 100% release rate may bethe "window of opportunity" of egg release in S． thunbergii． These findings giveinsight into the egg release in S． thunbergii under laboratory conditions．
The development of ovum and zygote，and the growth of juvenile sporophytewere observed on the laboratory conditions． Eggs adhered to the receptacle followingrelease from their conceptacles． The zygote detached from receptacle 20 happroximately after fertilization． After taking transverse division twice，one terminalcell developed into rhizoid and the two others developed into the germling． Thedevelopment of lateral branch started when juveniles grew up to 2ram in length．
Commercial farming of S． thunbergii is being developed in China． Asynchronousdischarge of gametes and growth of epiphytie algae are the two main constraints forthe seedling production of this species． In this study，40% and 65% reproductiveoutput for nature and farmed population were respectively recorded during peakreproduction． Furthermore，lower degree of temporal dispersion of germlingoccurrences for farmed population in related to nature ones was found，althoughgermling occurrence exhibited significant temporal variations for both populations．These results indicated that using farmed population as parental plants to collectgermlings is an effective strategy in achieving mass discharge of gametes． At the peakperiod of discharge，as more as 3.2×105 germlings per kg wet weight plants from thefarmed population was obtained，which was significantly more than that of natureones and could meet the demand of large scale seedling production． Anotherconstraint (i．e． growth of epiphytic algae) interfering the seedling cultivation wasattempted to eliminate by a strategy of jet-washing and high density seeding． Theattachment capacity of germlings was found to be significantly increased with theduration of attachment． A detachment of less than 10% was observed on collectorsthat were jet-washed using an intensity of 1 kg cm-1 by 48 h post-attachment，whichenables the jet-washing to be early conducted，thus preventing the growth of epiphyticalgae from early life stage． High density had adverse effects on length mean，sizeequality and occurrence of branches of germlings． However，30-50 individuals cm-2were thought to be usable in the seedling production of S． thunbergii，because theyunderwent less density effects，and withstood the impact of continual jet washing． Noevident epiphytic algae growing on collectors or adhering to host plants were observed in the
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摘要 :
The21stcentury has marked significant changes in world economic development,with new countries developing rapidly.However,with changes on the national arena the world faced new challenges concerning not only economy development,bu...
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The21stcentury has marked significant changes in world economic development,with new countries developing rapidly.However,with changes on the national arena the world faced new challenges concerning not only economy development,but worldwide ecological situation as well.The most acute issue for every country(developing or developed)has become a way to maintain steady growth both in terms of economic and ecological development.
It comes without any doubt that the economic growth of any country is needed to reduce poverty,foster nation's wealth and achieve prosperity for all.However,it has shown that the ways of achieving economic development which are being employed now cannot serve as a long-term solution to global economic problems and have to be elaborated in compliance with the principles of sustainability.
The study aims at revealing and comparing sustainable development strategies in Russia and China,the countries which are close not only in terms of borders but in terms of economic and political ties as well.It also aims at analyzing countries'approaches to the greening of economies,identifying possible environmental economic issues of the countries'cooperation as well as possible challenges connected with the countries'efforts to achieve steady economic growth beneficial to environment as well.The purpose of the study is to find out and analyze possible lessons for China and Russia which can be learnt from each other in the countries'transition to sustainable economic systems.
The research carried out in the paper reveals and analyzes sustainable development levels in both Russia and China.The results of the empirical analysis prove the crucial importance of urbanization for sustainable development in Russia and define several other factors and conditions which influence the levels of sustainable development in both countries.
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摘要 :
Like the majority of developmental studies, studies on the development of bilingualism(BL) has also recognized the importance of individual-environment interaction in thedevelopment of bilingual abilities.Factors ranging from pers...
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Like the majority of developmental studies, studies on the development of bilingualism(BL) has also recognized the importance of individual-environment interaction in thedevelopment of bilingual abilities.Factors ranging from personal characteristic, such as age andgender, family members and peers, social structure, up to popular culture can affect the outcomeof individuals' development; however, understandably, in most researches, due to the difficultyof controlling and dealing with all such factors, they are excluded from analyses, resulting in theless conclusive results.Thus, now that there are fair amounts of research on various aspects ofbilingual development, it is perhaps time to ask broader questions about the way those factorscontributes to the observed variations.Ecological theory, according to which the mutualinteraction of an individual with his/her context takes place under four levels of intertwinedenvironmental influences, has been shown to be a successful developmental model and it wouldbe an appropriate framework to take to make a better understanding of individuals' developmentof language.This thesis would be a holistic review based on such an approach, starting with theintroduction of ecological theory and language; next, after defining different types ofbilingualism and bilingual education (BE), some myths surrounding these issues will bediscussed, and then some actual findings and facts about the difference of bilinguals andmonolinguals will be revealed.As discussed in this paper, many well established studies havepointed out the reasons leading to the existence of such myths, and have shown and supportedthe long lasting advantages of bilingualism over individuals' language and cognitivedevelopment.The rest of the paper then, beyond the simple idea of whether bilingualism is goodor bad, attends to how different factors interact with BL/BE at each level of person-contextinteraction; following by a summary and conclusion about the set of individual and contextualconditions that apparently enhance the advantages of bilingualism in a holistic view.Finally,paper ends with some recommendations and calls upon more comprehensive researches for thefuture in further areas that currently lack sufficient empirical finding in the literature.
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