杉科植物的表皮结构研究及古环境重建

全球古近纪和新近纪气候波动明显，很多科学家对古近纪和新近纪生物演化和气候演变规律的定量研究给予了相当的重视。杉科植物有长期发展的历史、少数的现存种和丰富的化石记录，成为指示古环境的理想植物之一。利用杉科植物重建古环境，首先要对化石植物进行正确的分类鉴定。杉科各属枝叶形态特征变异幅度较大，且枝叶排列和形态特征近似，有时各属之间存在交叉特征。杉科化石标本通常仅保存枝叶形式，且多个属的化石标本经常发现于同一地层，因而分类鉴定比较困难。植物的叶表皮结构是压型植物化石细胞信息的重要来源，是属种分类鉴定重要依据之一。本文在以往研究的基础上，完整分析了杉科9属现生植物的表皮特征，建立了杉科化石植物分类鉴定的现生植物的表皮特征参照系。 杉科植物的叶多为条形、钻形、鳞形或披针形，同种植物有1种、2种甚至3种叶型。其中水杉属的叶交互对生，其它属的叶螺旋状互生。水杉属的多数表皮细胞垂周壁明显弯曲，落羽杉属和杉木属有时微呈波状，其他属的表皮细胞垂周壁直。多数植物的叶片近轴面和远轴面的气孔数量和分布不同。一般来说，条形叶和披针形叶的远轴面气孔分布状况和气孔数量稳定，远轴面的中部最稳定。条形叶远轴面的气孔分布于中脉两侧，形成纵向的气孔带。条形叶近轴面气孔分布状况和气孔数量变化大，近轴面的气孔数量有时与远轴面近似，但多数情况下比远轴面少，有时整个叶片的近轴面仅少数几个气孔或没有气孔分布。钻形叶的近轴面和远轴面的气孔数量近似，或叶片近轴面的气孔数量比远轴面的气孔数量多，气孔分布范围也比远轴面气孔分布范围广。气孔椭圆形，落羽杉属植物和水松鳞形叶的气孔长轴方向与叶片长轴垂直或斜向排列，柳杉属植物的气孔多斜向排列，水松的条形叶和条状钻形叶的气孔多平行向排列。落羽杉属和柳杉属以外的杉科植物的气孔长轴多数与叶片长轴平行。在扫描电子显微镜下的密叶杉属植物叶片角质层的内表面，副卫细胞和表皮细胞的垂周壁与叶表面的角度一致，且副卫细胞的形态与表皮细胞类似，这种特殊气孔器被称为A-型气孔器。杉科植物中水杉属、落羽杉属和杉木属的气孔器近似密叶杉的这种A-型气孔器。台湾杉属、柳杉属、水松属、红杉属和巨杉属植物的气孔器与这种A-型气孔器不同，这几属的副卫细胞垂周壁表皮细胞的垂周壁方向不同，且副卫细胞的形态与表皮细胞的形态明显不同。因而气孔所有副卫细胞组成呈明显的圆盘状，保卫细胞在盘子的中央。综合分析植物的枝叶形态和表皮特征可以区分杉科各属。 本文研究了采自抚顺始新世的杉科植物标本，经枝叶特征、表皮结构和球果鳞片等特征分析为水松属的欧洲水松。论文分析了中国东北地区古温度定量研究结果与杉科植物的相关性。抚顺植物群发现有化石水杉M. occidentalis、中华红杉和欧洲水松，根据这三种化石植物的年均温度和年降水量，通过共存分析，推测抚顺始新世的年均温为12.1-17℃，年降水量为1199.6-2231mm。

影响汉语阅读能力发展的相关认知因素及其作用的发展变化

The present cross-sectional study paid attention to Chinese reading acquisition of 391 children from preschool to grade 3 in two elementary schools, and investigated the relationship between orthographic processing skills, morphological awareness, phonological awareness, naming, phonological memory, visual processing skill and reading skills, after controlling the variance of age, nonverbal intelligence and pinyin knowledge. The main results are as follows: Firstly, there are many different language skills as the predictors of Chinese reading success. Orthographic processing skills, morphological awareness, phonological awareness and naming are important in single-character recognition and comprehension. Beside them, the effect of visual processing skill and phonological memory for comprehension are also significant. Among them, the role of orthographic processing skills is the most important, whatever in single-character recognition or in comprehension. Secondly, orthographic processing skills are the most important factors in reading acquisition at low grade and its effect drops obviously after grade 2. Thirdly, morphological awareness is also the factor that cannot be ignored whatever for single-character recognition or for comprehension. Its influence appears in preschool and becomes the only significant predictor of character recognition in grade 3. Furthermore, morphological awareness is more relevant with the development of comprehension. Fourthly, phonological awareness plays the secondary role in Chinese reading acquisition except in grade 2 when its contribution is most of all. And compare with morphological awareness, the effect of phonological awareness is relative low. Fifthly, naming is important through preschool to grade 2. The contribution of phonological memory increases from preschool to grade 3 in comprehension.