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亚硫酸氢钠对转PEPC基因水稻叶片光合作用的促进作用 总被引：4，自引：0，他引：4
用1～2mmol／L的NaHSO3喷施于野生型水稻Kitaake(WT)、以其为基因受体的转PEPC基因水稻(PC)和转PEPC PPDK双基因水稻(PC PK)叶面．叶片的光合速率分别提高了23．0％、28．8％和32．4％，并能持续3d左右．在此条件下，光下叶片中的ATP含量提高．将已知可促进循环光合磷酸化的辅助因子硫酸甲酯吩嗪(PMS)和NaHSO3分别和共同喷洒叶片，次日所有叶片的光合速率均比对照(喷水)提高，共同处理未出现叠加效应，表明NaHSO3的主要作用和PMS促进光合速率的原因类似，都是增加了ATP的供应．与野生型水稻Kitaake(WT)相比．经NaHSO3处理后，转PEPC基因水稻(PC)净光合速率增加的幅度大，转PEPC PPDK双基因水稻(PC PK)净光合速率增加的幅度更大，因此认为水稻叶片中增加ATP的供应可明显增强水稻的光合速率，特别是转PEPC或PEPC PPDK基因水稻． 相似文献
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长柄串珠藻生理生态特性的研究 总被引：2，自引：0，他引：2
孙存华刘晓峰刘贤德郭晓薇郭东城徐金平刘晓燕华栋 《资源科学》2001,23(3):93-96
长柄串珠藻是一种要求水温较低且恒定并适应光强较弱的小型淡水红藻，生存于Ph7.5,夏天水温为17°C ,冬天水温为14°C ，全年水温波动不大，钙含量较高而其它营养盐分含量较低的泉水中。奇光合作用的最适水温为15°C ，光合作用的适宜强光为30μmol/m2.s-50μmol/m2.s，最适光强度为35μmol/m2.s-45μmol/m2.s，40μmol/m2.s光合速率最高峰，为其饱和光强。长柄串珠藻的光补偿点随温度的升高而升高，5°C、10°C、15°C、20°C和25°C的光补偿点分别为4.5μmol/m2.s、5μmol/m2.s、5.6μmol/m2.s、6μmol/m2.s和7μmol/m2.s。呼吸速率在光合速率增大时也升高，且与水温正相关 相似文献
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不同品种黄瓜幼苗光合机构对盐胁迫的响应 总被引：26，自引：0，他引：26
研究了盐胁迫(0、25、50mmol／L)对不同品种黄瓜幼苗生长、光合作用和叶绿素荧光的影响．结果表明，盐胁迫，尤其是高浓度NaCl(50mmol／L)的胁迫，显著降低黄瓜幼苗生长量、叶绿素含量、光系统Ⅱ光合电子传递量子效率(φPSⅡ)、净光合速率(Pn)、气孔导度(Gs)以及气孔限制值(Ls)，同时显著提高叶片相对电导率、丙二醛、脯氨酸含量和细胞间CO2浓度(Ci)，光系统Ⅱ的光化学效率(Fv／Fm)变化不大．盐胁迫对耐盐黄瓜‘津研4号’幼苗生长的影响小于盐敏感黄瓜‘津绿4号’，这可能与耐盐黄瓜在盐胁迫下较高的净光合速率、光系统Ⅱ光合电子传递量子效率和较低的丙二醛(MDA)含量、相对电导率有关。 相似文献
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中国亚热带红壤丘陵区不同土地利用方式下土壤CO2排放规律初探 总被引：26，自引：2，他引：26
以千烟洲试验站为例 ,对亚热带红壤丘陵区杉木林、柑桔园、玉米地、水稻田四种不同的土地利用方式下的土壤CO2 年排放总量、排放速率的年变化和日变化进行了详细的比较。 4种土地利用方式下CO2 年排放总量从高到低依次为玉米地 5 799kg·m- 2 、柑桔园 4 1 76kg·m- 2 、水稻田 3 388kg·m- 2 、杉木林3 1 1 9kg·m- 2 。研究发现 ,4种土地利用方式下的土壤CO2 排放速率均是夏季高于冬季 ,白天高于夜间。此外 ,本文还分析了土壤温度、土壤湿度和人类活动等因子对土壤CO2 排放速率的影响 ,发现土壤二氧化碳排放速率与 5cm地温存在显著的指数正相关关系。 相似文献
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在玉米抽雄期进行了水分胁迫实验，利用Licor-188B和Licor -6200便携式光合作用测定系统测定了水分胁迫对玉米光和作用的影响状况，在此基础上建立了冠层光和生产力计算公式。计算结果表明：当叶面积指数为5时，水肥适宜状况下黄淮地区夏玉米日总光合量变化在95g.m-2至105g.m-2 & 黄淮海地区、夏玉米、水分胁迫、 相似文献
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西藏高原农田生态系统土壤呼吸的日变化和季节变化特征 总被引：21，自引：0，他引：21
通过对西藏高原农田生态系统土壤CO2排放状况的观测，讨论了高原冬小麦、青稞和对照裸地的土壤CO2排放日变化和季节变化的特征。冬小麦、青稞和对照裸地的CO2排放的最高点和最低点分别发生当地时间的13:00~14:00和凌晨5:00~6:00左右，但在越冬期土壤CO2排放已很微弱，日变化不明显。冬小麦和青稞地的土壤CO2排放最高值出现在灌浆初期, 可达到40 g m-2 d-1左右；收割后，气温和土壤温度也逐渐降低，土壤中的微生物和小麦根系的呼吸减弱，土壤CO2排放一般为20 g m-2 d-1以下；至越冬期，土壤CO2排放降至2 g m-2 d-1左右，土壤CO2排放非常微弱。高原农田土壤CO2排放与5cm土壤温度变化相关性最好，可用5cm土壤温度来推算高原冬小麦地的土壤CO2排放量，并由此得到在灌浆期高原冬小麦的根系呼吸所排放的CO2量占整个土壤的CO2排放量的34～44%，平均为40%。 相似文献
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在玉米抽雄期进行了水分胁迫实验 ,利用Licor 1 88B和Licor 6 2 0 0便携式光合作用测定系统测定了水分胁迫对玉米光合作用的影响状况 ,在此基础上建立了冠层光合生产力计算公式。计算结果表明 :当叶面积指数为 5时 ,水肥适宜状况下黄淮海地区夏玉米日总光合量变化在 95g·m- 2 至 1 0 5g·m- 2 之间 ,最高值出现在河南和山东两省交界处 ;当土壤湿度下降至田间持水量的 4 0 %时 ,该地区冠层光合日总量平均降低 5 0 %左右 ;水分胁迫对不同地区冠层光合日总量存在不同的影响 ,在夏玉米抽雄期水分胁迫对山东省玉米冠层光合日总量影响最大 ,水分增产潜力最高 ,此时为夏玉米水分关键期 ,及时灌溉非常必要 相似文献
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Marjorie Armstrong-Stassen Margaret Landstrom Ramona Lumpkin 《The Information Society》1998,14(2):153-164
This study examined how students who had no prior experience with videoconferencing would react to the use of videoconferencing as an instructional medium. Students enrolled in seven different courses completed a questionnaire at the beginning of the semester and again at the end of the semester. Students at the origination and remote sites did not differ in their reactions toward videoconferencing but there was a significant difference for gender. Women reacted less favorably to videoconferencing. Compared to the beginning of the semester, students reported significantly less positive attitudes toward taking a course through videoconferencing at the end of the semester. There were no significant differences in students' attitudes toward videoconferencing across courses at the beginning of the semester but there were significant differences across the courses at the end of the semester. The results suggest the need for better preparation for both students and instructors. 相似文献
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A joint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology his co-workers from Norway US Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells suggesting that China's projected climate warming could decrease the pest's numbers. The study was published in Proceedings of the National Academy of Sciences on September .…… 《中国科学院院刊(英文版)》2008,22(1):6-7
Ajoint study by Prof. ZHANG Zhibin from the CAS Institute of Zoology and his co-workers from Norway, US and Swiss have indicated that historical outbreaks of migratory locusts in China were associated with cold spells, suggesting that China＇s projected climate warming could decrease the pest＇s numbers. The study was published in Proceedings of theNational Academy of Sciences on 17 September, 2007. 相似文献
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Caroline Haythornthwaite 《The Information Society》2001,17(3):211-226
A computer-mediated group is a complex entity whose members exchange many types of information via multiple means of communication in pursuit of goals specific to their environment. Over time, they coordinate technical features of media with locally enacted use to achieve a viable working arrangement. To explore this complex interaction, a case study is presented of the social networks of interactions and media use among members of a class of computer-supported distance learners. Results show how group structures associated with project teams dominated who communicated with whom, about what, and via which media over the term, and how media came to occupy their own communication niches: Webboard for diffuse class-wide communication; Internet Relay Chat more to named others but still for general communication across the class; and e-mail primarily for intrateam communication. Face-to-face interaction, occurring only during a short on-campus session, appears to have had a catalytic effect on social and emotional exchanges. Results suggest the need to structure exchanges to balance class-wide sharing of ideas with subgroup interactions that facilitate project completion, and to provide media that support these two modes of interaction. 相似文献
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《中国科学院院刊(英文版)》2008,22(1):2-3
CAS should stick to the principle of rendering service to, and giving impetus for, the development of China＇s science enterprise by making S＆T innovations, said CAS President LU Yongxiang. The CAS president made the remarks in a recent talk to communicate the gist of the winter session of the Party＇s Leading-member Group at CAS, which was held from 7 to 11 January in Beijing. 相似文献
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Electronic data interchange (EDI) provides means for interorganizational communication, creates network externalities, requires an advanced information technology (IT) infrastructure, and relies on standards. In the diffusion of such innovations, institutional involvement is imperative. Such institutions contain governmental agencies, national and global standardization organizations, local government, and nonprofit private organizations like industry associations. The last type of organizations we call intermediating institutions. They intermediate or coordinate ("inscribe") the activities of a group of would-be adopters. Unfortunately, little is known of how these organizations shape the EDI diffusion trajectory. In this article we examine one specific type of intermediating organizations?industry associations?and how they advanced the EDI diffusion process in the grocery sectors of Hong Kong, Denmark and Finland. We identify six institutional measures, placed into a matrix formed by the mode of involvement (influence vs. regulation) and the type of diffusion force (supply push vs. demand pull), that can be mobilized to further the EDI diffusion. Industry associations were found to be active users of all these measures to varying degrees. Their role was critical especially in knowledge building, knowledge deployment, and standard setting. Furthermore, institutional involvement varied due to policy and cultural contingencies and power dependencies. 相似文献
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《中国科学院院刊(英文版)》2008,22(1)
With great care, Dr. ZHOU Zhonghe takes out a package wrapped by cotton tissue from a drawer and says: "This is the gem of our collections: the fossil of a bird that lived 125 million years ago!" Then, pointing at a tiny mound, he explains: "Look, this is the claw and that is the head. It was in the egg shell and ready to hatch ... The species fell into a family of waterside inhabitants." 相似文献
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Puay Tang 《The Information Society》1998,14(1):19-31
The increasing prospects of digital piracy has prompted the perceived need by electronic publishers to adopt technical systems of protection, and governments to reform their copyright laws. This article is a preliminary study of the management of intellectual property by electronic publishers, defined as those involved in the production of online databases, and CD-ROMs. It focuses on three main issues: (1) how electronic publishers view the increasing threat of piracy; (2) the methods of protection employed to protect intellectual property in digital format; and (3) the importance of technological protection of intellectual property in electronic publications. The analysis is based on a sample of 23 UK electronic publishers. The interviews revealed an interesting assortment of protection methods and did not show that technological protection was a preferred way. Instead, the means of protection, in addition to copyright law, comprised niche markets, pricing, trust, bad publicity, and nontechnical and technical means. 相似文献
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Milton Mueller 《The Information Society》2001,17(3):151-163
Long-standing conflict between domain name registrants and trademark holders prompted the Internet Corporation for Assigned Names and Numbers (ICANN) to create a global, mandatory arbitration procedure known as the Uniform Dispute Resolution Policy (UDRP). The UDRP has been used in 2166 cases involving 3938 domain names as of 1 November 2000. The policy gives the initiator of a complaint, generally a trademark holder, the right to choose which ICANN-accredited dispute resolution service provider (RSP) will handle the case. During the preparation of the UDRP,some feared that complainant selection would lead to "forum shopping" that might bias the results. This article performs a statistical assessment of the forum-shopping thesis and finds support for it. There are statistically significant differences in the various RSPs' propensity to take away names from defendants; there are also major differences in the number of cases brought to each RSP. RSPs who take away names have the larger share of cases. The study examines other variables that might explain differences in market share, such as price, the plaintiff's nationality, or the time taken to decide a case. It finds that nationality and time also are correlated with market share. The study concludes that shopping for a favorable outcome is an important factor in the UDRP. 相似文献
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Prof. Raymond C.K. Chen a neuropsychologist with the CAS Institute of Psychology has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology.…… 《中国科学院院刊(英文版)》2008,22(1):15-15
Prof. Raymond C.K. Chen, a neuropsychologist with the CAS Institute of Psychology, has made novel progress in his studies of schizophrenia. His work has been reported by a recent issue of Behavioural Neurology. 相似文献
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Leah A. Lievrouw 《The Information Society》1998,14(2):83-96
The main premise of this article is that in information societies generally, and in virtual social contexts particularly, a distinctive style of interaction to facilitate the communication of difference, heterotopic communication , has emerged. It rests on two cultural foundations: an ideological belief in the positive, socially integrating power of communication, and a prevailing ethic of instrumental rationality, subjective individualism, and strategically practiced self-interest. The former is demonstrated by the use of simulation and spectacle as sources of information; exhibitionism/voyeurism as a communicative style; and the awareness of surveillance. The latter is seen in the competitive use of knowledge as a commodity; a surface globalism masking deep parochialism; lateral as well as vertical information inequity; and the use of public versus private as strategies for engagement rather than as spaces. Those who engage in heterotopic communication resort to their 'own devices' both in the sense of personal agendas, strategies, interests, and interpretations, and in the form of the telecommunication tools that help realize them. These personal and technological devices allow individuals with the right educational and technical resources to avoid exposure to disagreement, difference, or other information that does not serve their direct purposes or reflect their particular views of the world; yet they also help convey the appearance of openness, availability, and cooperation. This style of interaction is used strategically in combination with information and communication technologies to gain social or economic advantages, but it may encourage social separatism and parochialism, inhibit the negotiation of disputes, and emphasize competing interests. 相似文献