Sap flow response of Eucaylyptus (<Emphasis Type="Italic">Eucalyptus urophylla</Emphasis>) to environmental stress in South China

Sap flow and environmental conditions were monitored at two Eucalyptus (Eucalyptus urophylla S.T. Blake) plantations at Hetou and Jijia, located in Leizhou, Zhanjiang, Guangdong Province. It was found that daily sap flux density (SFD) of Eucalyptus was closely related to daily atmospheric vapor pressure deficit (VPD) (R ²=0.76, P=0.01 at Hetou and R ²=0.7021, P=0.01 at Jijia) at both sites. No significant relationship existed between daily SFD and mean daily air temperature at both sites. Daily SFD varied with wind speed Y=−17585X ³+15147X ²−1250.7X+2278.4 (R ²=0.68; P=0.01) at Hetou and Y=−101.67X ³−1.65X ²−376.4X+1914.8 (R ²=0.40, P=0.05) at Jijia, where Y was daily SFD, X was daily wind speed. Experimental observations yielded the following data: (1) the critical lower and upper daily VPD threshold were 0 and 2 kPa, within which daily SFD varied from 540±70 L/(m²·d) to 4739±115 L/(m²·d) at Hetou site, from 397±26 L/(m²·d) to 3414±191 L/(m²·d) at Jijia site; (2) Diurnal SFDs at Hetou site were much higher under low relative humidity (<30%) and slightly lower under high relative humidity (>80%) compared with those at the Jijia site; (3) The upper and lower threshold of daily and diurnal RAD for the optimal water use of E. urophylla plantations were 18±2.7 and 2±1 MJ/(m²·d), 669 and 0 J/(cm²·h) during the observation period. Project supported by Knowledge Innovation Funds from Chinese Academy of Sciences (Nos. KSCX2-SW-120, KZCX1-SW-01-01A3) and the Key Project of Guangdong Natural Science Foundation (No. 010567), China     

Na?ve Students’ Conceptual Development and Beliefs: The Need for Multiple Analyses to Determine what Contributes to Student Success in a University Introductory Physics Course

This research involved na?ve physics learners who were interested in majoring in science or engineering. In a semester-long quasi-experimental study, open-ended pretests and weekly interviews were used to analyse the progressive development of students’ conceptions relating to sound and wave motion. Semi-structured interviews were also conducted to elucidate: (1) how their conceptions developed from everyday conceptions to unclear scientific conceptions to scientific conceptions, and (2) their beliefs of physics knowledge. Despite efforts to enable these students to learn physics, the findings showed that only two out of ten students developed acceptable physics conceptions during the course that would enable them to pursue the subject to a higher level. Also, students’ conceptual development was found to be related to their cognitive understanding and to epistemological beliefs of physics. Therefore, to facilitate na?ve physics learners’ success in a general physics course, in addition to the acquisition of content knowledge, explicit emphasis needs to be placed on the nature of physics knowledge.     

菊科莴苣属订正及亚洲大陆菊科植物二新属

本文是对菊科莴苣属Lactuca L. 的分类订正, 文中起用了乳苣属Mulgedium Cass.和山   莴苣属Lagedium Sojak两个较老的属名, 建立了二个新属，即翅果菊属Ptrocypsela Shih与假   福王草属Paraprenathes Chang. 文末提供了莴苣属及邻近属以及东亚地区的有关种类的分属分种检索表。     

我国生物安全问题的现状分析及对策

在跨越了改变自身以适应环境和改变环境以适应自身的两大历史阶段之后,人类社会已进入到既能改变环境又能改变自身的历史新时期。由生物技术带来的安全风险具有人类历史发展的必然性,只能面对而不能回避。除空天、海洋、网络、传统安全外,生物威胁已上升为新的安全疆域,在当前我国重要战略机遇期构成了全新的安全需求。文章简述了自SARS暴发以来国内外生物安全问题的发展态势,深入分析了当前我国所面临生物安全威胁的现实特点。在对前人所做生物安全问题研究的基础上,总结归纳出了生物安全理论的框架。同时,以生物安全理论内涵为指导,对未来我国所面临生物安全威胁的发展走向进行了预测,提出了以新观念主导战略能力建设、以理论创新主导科技支撑、以体系应对新型生物性危害的实施策略。     

菊科亚菊属川甘亚菊类群订正

本文对作者本人在1983年《中国植物志》第76卷第一分册12l页上针对川甘亚菊处理过宽的问题，重新作出了订正。本文确认川甘亚菊、灰叶亚菊、深裂亚菊及下白亚菊分别为不同的种，并作出了这四个种的分种检索表。     

热水溶液中CH_4和CO_2之间碳同位素交换的初步研究

230℃和250℃温度下溶液中CH_4和CO_2之间的碳同位素交换反应的实验初步证实它们在水溶液中要比在于系统中容易进行同位素的交换。不同条件实验的比较表明溶液的酸度(或pH)、CH_4/CO_2(摩尔)和反应容器的大小等都会明显地影响同位素交换的速度。文中描述了实验方法,并从机制上初步讨论了实验结果。     

科研工作的时效性探讨

通过对科研工作时效性的理论思考,结合科研工作的实际和案例分析,对科研工作时间投入和科研效益的若干问题进行初步的探讨。     

三种数值方法在几种六道木分类中的应用

   In the last 10—20 years there has bee n increasing awareness of the problem con- cerning the aims and practices of taxonomy.  In particular, there has been growing interest in the development of numerical methods in biological taxonomy as an aid to making systematics a quantitative science, a step which comes in time to almost every scientific discipline.       Numerical taxonomy is the evaluation by numerical methods of the affinity or  similarity between taxonomic units and the employment of these affinities in erecting a hierarchic order of taxa.  The present rapid development of these ideas is presuma- bly a result of the development of computer techniques.       Numerical taxonomic approach has been applied to the studies of entomology and microbiology in China to some extent since 1975. But so far it hasn’t been commonly used in botany.  The present report is a preliminary study on 9 spp. of the genus Abelia.  A set of binary data with 54 characters  is  used  for  computing association coefficient; and a set of quantitative data with 47 characters for distance coefficient and correlation coefficient. For the mathematical models were chosen the non-metric  simple matching association coefficient, the geometrical distance of Riemannian space and correlation coefficient.  Computational procedures are stepwise presented in detail and computer programmes are written in the background of Algol-60 language. Cluster analysis is compared with simple linkage,  average  linkage  and multi-correlation.      The results of DC and CC for 9 spp. of Abelia agree closely with the traditional taxonomy, because the data we collected mainly come from morphological characters. It would seem that the results of quantita tive data are more appropriate for  seed plants.  It is, therefore, postulated that our programes are complementary and very useful to a wide range of classification entities, such as microbes, animals and plants in present situation in China.      In conclusion, a comparison between the  conventional taxonomy  and  numerical taxonomy has been made, and a brief discussion of three problems, i.e. the monothetic versus polythetic, divisive versus agglomerative, weighting versus unweighting.