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101.
In the work mitotic chromosomes in root-tips of 7 species native to Sichuan Pro-
vince were examined and their karyotypes were analysed based on 7-8 cells at mitotic meta-
phase, using Levan et al.'s (1964) nomenclature. The list of species and origin of the materials
used in this work are provided in the appendix. The micrographs of mitotic metaphase of all
the materials are shown in Plates 1 and 2; the idiograms in Fig. 1, 1-9, and the parameters
of chromosomes are provided in Tables 1-9. All the chromosome countings and karyotypes in
this paper are reported for the first time.
Characteristics of the karyotypes may be summarized as follows:
1. 2n=38 are found in all the materials except A. sichuanensis, which has 3 cytotypes, i.e,
2n=38+5B, 2n=38+lB and 2n=38+OB (Plate 2, 1-2, Fig. 1, 5-6).
2. The karyotypes are of two major types: the karyotype of A. flaviflora falls into 3C in
Stebbins's (1958, 197l) classification of karyotypes and those of all the other species into 2C.
The two types are also different from each other in the number of large and medium-sized
chromosomes pairs and morphology of the first pair of chromosomes (compare Plate 2, 5, Fig.
1, 9 with the other micrographs and idiograms).A. flaviflora with the karyotype 3C also differs
from the other species in a series of gross morphological characters: the species is of a yellow and
campanulate corolla.
3. The species with caespitose leaves (A. caespitosa and A. omeiensis) have essentially the
same karyotype, which is rather different from those of the species with scattered leaves. There
are two pairs of small sm chromosomes (arm ratio ≥1.90) in the former karyotype (Tables 1
and 3), but all the small chromosomes are m or sm with arm ratio <1.80 in the latter karyotypes. 相似文献
102.
M.Tahir Khaleeq Lang Wengpeng He Guoseng 《上海大学学报(英文版)》1998,2(2):127-134
NomenclatureAArea(m2)DhHydraulicDiameter(m)EEnergyContent(J)fPressureLossCoeficientαVoidFractionHSpecificEnthalpy(J/kg)IInert... 相似文献
103.
在本文中我们讨论了α次积分半群的收敛与逼近,获得了α次积分半群的Trotter—Kato定理,并将其结果应用于Banach空间中完全二阶微分方程的讨论。 相似文献
104.
李浪 《湖南科技学院学报》2005,26(5):147-149
本文对计算机网络安全中黑客入侵的主要手段进行了概括和分类,并提出了相应的解决对策;并对黑客入侵提出了整体防范策略和措施。 相似文献
105.
106.
107.
浪漫主义文学是英国文学史上的一树奇葩,华兹华斯是浪漫主义的开拓者、引路人,而雪莱则是浪漫主义文学巅峰时刻的最重要诗人,他们的作用可谓举足轻重。本文通过从他们诗歌以至人生思想的演变中所表现的价值观进行比较分析,指出这两位浪漫主义诗人各自诗歌思想的演变,即华兹华斯对革命由激情到失望,而雪莱则一如既往,奋斗不息。这有助于读者将诗人的诗歌与思想相联系,进一步了解他们诗歌的社会意义,评价两位杰出诗人在诗歌创作上的独特成就。 相似文献
108.
通向自由的艰难之路——我国开放存取的现状分析 总被引:3,自引:0,他引:3
目前,多数研究误将我国开放存取发展缓慢的原因归结为知识产权对开放存取的威胁、质量控制的制约、付费模式脱离实际等因素.实质上,政府、机构、期刊和研究者对开放存取的认知度过低才是问题的关键.基于问题的核心因素,我国开放存取的发展需要政府采取有效的措施加以引导、机构的认可与重视、学术期刊的积极参与、研究者的支持. 相似文献
109.
We tested the effect of voluntary peer-facilitated study groups on student learning in large introductory biology lecture classes. The peer facilitators (preceptors) were trained as part of a Teaching Team (faculty, graduate assistants, and preceptors) by faculty and Learning Center staff. Each preceptor offered one weekly study group to all students in the class. All individual study groups were similar in that they applied active-learning strategies to the class material, but they differed in the actual topics or questions discussed, which were chosen by the individual study groups. Study group participation was correlated with reduced failing grades and course dropout rates in both semesters, and participants scored better on the final exam and earned higher course grades than nonparticipants. In the spring semester the higher scores were clearly due to a significant study group effect beyond ability (grade point average). In contrast, the fall study groups had a small but nonsignificant effect after accounting for student ability. We discuss the differences between the two semesters and offer suggestions on how to implement teaching teams to optimize learning outcomes, including student feedback on study groups. 相似文献
110.
This research investigated 68 secondary school students’ perceptions of their computer-mediated project-based learning environment
and their attitudes towards Project Work (PW) using two instruments—Project Work Classroom Learning Environment Questionnaire
(PWCLEQ) and Project Work Related Attitudes Instrument (PWRAI). In this project-based learning environment, students experienced
a face-to-face classroom setting and e-learning by using a synchronous computer-mediated communication (CMC) tool called ‘iCollaborate’
for online communication and project collaboration with peers from other countries. The PWCLEQ and PWRAI instruments were
used to evaluate the computer-mediated project-based learning environment using students’ perceptions of the learning environment
and to further investigate how their perceptions might affect their attitudes towards PW lessons. Students perceived the computer-mediated
project-based learning environment favourably but they preferred to experience more Material Environment and more Open-Endedness
and Social Presence. Simple correlation analysis revealed that all environment dimensions were significantly and positively
related to the students’ attitudes towards PW, while multiple regression analysis indicated that two scales, Instructor Support
and Social Presence, were the strongest predictors of attitudes towards PW lessons. 相似文献