掌鳞杉科植物的形态解剖及古环境气候

Cheirolepidiaceae is an important Mesozoic conifer family which has been recorded from the Late Triassic to Late Cretaceous. The family displays a quite remarkable range of morphology and the acme of diversification in the Early Cretaceous. In order to have a better understanding of biology, development and phylogenetic relationships of fossil plants and the palaeoclimate and palaeoenvironment, in the last few decades modern palaeobotany focused on study and reconstruction of whole fossil plants. Although China has very abundant fossil records of Cheirolepidiaceae in the Mesozoic deposits, the anatomy of the vegetative and especially reproductive organs of the Mesozoic Cheirolepidiaceae plants in China remains traditionally not well documented. It is necessary to obtain an abundant material by mass collecting to study and reconstruct fossil plants partly or entirely. This program will study the morphology, anatomy and ecology of some structurally perserved cheirolepidiaceous conifers from the late Mesozoic of China by using modern techniques and methods, such as bulk maceration and transferring and turning over to get cuticle and pollen, embedding technique and sectioning to get thin 1 μm and ultrathin 60-70 nm sections very rich in precise data. All samples, including fossils, cuticles, pollen and sections will be investigated using light and electron microscopy (LM, SEM, TEM). The study will focus on structurally very well preserved fossils and reproductive organs (male cones and female cones, isolated cone scales, in situ pollen and seeds). All vegetative and reproductive organs of cheirolepidiaceae or associated with them, impression or compression, petrifaction or permineralization, will be studied carefully and in detail in their morphology and anatomy. As other data to this pluridisciplinary approach, stomata density and index of epidermal cuticle will be used for assessing palaeoatmospheric carbon dioxide levels. In addition, many deposits of sediment bearing cheirolepidiaceous conifers will be analyzed palynologically. All these studies will contribute much not only to our knowledge of classification and phylogeny of Cheirolepidiaceae, but also to very fruitful interpretations of palaeoclimate and palaeoenvironment in a period In a wider point of view, this project could provide more reliable evidences for understanding phylogeny, evolution and extinction of cheirolepidiaceous conifers, and the vegetation evolution through geological history.

掌鳞杉（Cheirolepidiaceae）是已绝灭的松柏类植物，自晚三叠世开始出现，早白垩世呈现最大的形态学和属种分异度。本项目以"化石植物生物学"和"微细构造与整体重建"的学术思想为指导，运用浸解、移离、切片和超薄切片、光学显微镜结合扫描和透射电镜等技术手段，对我国晚中生代地层、尤其是早白垩世地层中的一些掌鳞杉科植物化石的外部形态和内部解剖进行全面研究，包括表皮角质层的显微和超微构造、矿化或丝炭化的木材解剖，同时特别注重生殖器官球果化石、原位花粉、胚珠种子等的形态解剖研究，以确凿的解剖学证据对部分掌鳞杉科植物整体复原与重建，探讨它们的自然分类系统，尝试分析掌鳞杉植物的表皮气孔参数的变化与大气二氧化碳浓度的关系；对几个相关剖面的岩石样品进行孢粉学分析。以植物形态解剖学和表皮气孔参数及孢粉分析，探讨晚中生代掌鳞杉科植物的生物学特性及多样性演化和古环境气候。

掌鳞杉科（Cheirolepidiaceae）是已绝灭的松柏类植物，自晚三叠世开始出现，早白垩世呈现最大的形态学和属种分异度，它在某一时期的出现通常认为此时期环境气候气候比较干热。中国中生代陆相地层中发现了大量的掌鳞杉，但只有少数几种得到详细研究。本项目执行期间运用各种技术手段对中生代、尤其是早白垩世地层中的掌鳞杉进行研究，结合能量色散光谱法分析表皮角质层及化石围岩的元素，探讨早白垩世掌鳞杉科植物的生物学特性和古环境特点。.对吉林省延吉汪清县罗子沟盆地大砬子组两种不同的掌鳞杉植物Suturovagina intermedia和Pseudofrenelopsis gansuensis做了细致的扫描和透射电镜电镜观察，完成了同一产地同一属不同的种、同一科不同的属的角质层的超微构造；首次完成了对来自吉林汪清和江苏南京不同产地的同一个种Suturovagina intermedia的超微构造的研究。研究结果表明用表明假拟节柏和缝鞘杉等属的掌鳞杉科植物的角质层都具有A1, A2, B1, B2层组成，尤其是独有的波状弯曲的A1层，显示了掌鳞杉科植物角质层超微构造的特点。在研究超微构造的同时利用能量色散光谱法(Elements Analysis by Energy Dispersive Spectroscopy)分析表皮角质层及化石围岩的元素组成，结合伴生的植物群特点分析了早白垩世中国东部的古环境气候，显示早白垩世晚期吉林延吉盆地古气候不如同期南京地区干热。统计了吉林延吉汪清罗子沟盆地和龙井智新盆地大砬子组两种掌鳞杉植物Pseudofrenelopsis dalazensis和Pseudofrenelopsis gansuensis的表皮气孔，利用气孔参数恢复了阿尔比期大气二氧化碳浓度大概在870 -1450 ppmv之间。本课题组在研究罗子沟掌鳞杉科植物的同时首次在大拉子组发现了似卷柏化石Selaginellites cf. fausta，也是我国目前发现的距今最近的似卷柏化石，丰富了我国似卷柏属的化石记录，似卷柏化石我国产有10种，其中早白垩世仅义县组报道有１种。.对新疆准噶尔盆地郝家沟、安徽灵璧和江西赣州的掌鳞杉科植物化石也进行了研究。.项目执行期间还系统总结了中国银杏植物化石，完成了西藏拉萨堆龙德庆邱桑寺早白垩世植物群研究。