【作者】 张泉；

【导师】 林金呈； 胡玉熹；

【作者基本信息】 中国科学院植物研究所 ， 植物学， 2001， 博士

【摘要】 在裸子植物系统学研究中，雌球果的形态与结构是最重要的性状之一。由于不同学者对裸子植物雌性生殖构造的形态学本质有着不同的见解，从而导致对该类群植物系统发育研究结果的差异。柏科在裸子植物中是唯一一个广布于南北两半球的科，前人对该科雌球果发育的研究涉及很少，为了进一步了解柏科植物雌球果的形态学本质，并为裸子植物传粉生物学和系统学的研究提供重要资料，本文选取了分布于北半球柏科中的7个属14个种，应用扫描电镜、半薄切片、石蜡切片及整体透明等方法，对其雌球果各部分的形态发生与发育过程作了详尽的研究，同时对传粉前后雌球果中的维管系统作了深入的分析。主要结果归纳如下： 1）雌球花苞片的形态、结构和排列方式等与叶相似；但传粉后，随着苞片基部的居间生长，其形态结构变得多样化； 2）在柏科7个属中，均未观察到种鳞发育，成熟球果的苞鳞得到充分发育； 3）各苞片腋内的胚珠发育过程，几乎是同时发育或呈向顶发育过程； 4）在圆柏属和柏木属球果顶端的苞片腋内也有胚珠发育，其它各属雌球花顶端的1-2对苞片腋内均没有胚珠发育； 5）在柏木属中，每一苞片腋内形成的胚珠数目较多，一般排成2-3行，同一苞片腋内的胚珠呈向基发育，同一行胚珠为离心发育； 6）圆柏属的雌球果发育呈现多种式样，其中包括由数枚侧生胚珠过渡到一枚顶生胚珠等情况； 7）柏科植物雌球花的维管系统在传粉前较为简单，即在苞片内仅具单一的维管束延伸到顶端，与营养芽相似。传粉后随着苞片基部的居间生长，其维管系统也随之复杂化。主要是在苞鳞内有新的维管束形成，一般是在苞鳞中间维管束的两侧各发出一束维管束，这两束维管束由球果轴发出的位置略高于中间一束，并在苞鳞基部迅速分枝，形成不同的排列式样。 成熟球果维管系统的排列方式与球果和苞鳞的形态有关，通常可分为三类：（1）具球形球果的种类，包括圆柏属、扁柏属、柏木属和福建柏属，其苞鳞内辐射状分枝的维管束形成两组，即一个具有水质部倒转的近轴系列和一个维管束正常排列的远轴系列；（2）在苞鳞中只形成一组倒转的维管束，如侧柏属和翠柏属；（3）崖柏属雌球果的苞鳞中没有倒转的维管束形成。 观察结果表明：柏科植物雌球果均为复轴性构造，其球果中胚珠着生在球果轴上是由于苞片腋内种鳞退化的结果，因而不支持柏科植物雌球果的种鳞与苞鳞完全合生的观点。 通过对柏科植物雌球果发育的研究结果，也为探讨松杉类植物雌球果的演化趋势提供了重要线索。长期以来，众多研究者均认为，松杉类植物雌球果的演化趋势是种鳞和苞鳞逐渐合并的过程，但从柏科植物雌球果苞鳞腋内种鳞退化现象的发现表明，松杉类植物雌球果的演化趋势可能是一种种鳞逐渐退化的过程。柏科的种鳞己完全退化，而苞鳞则相对发育。 依据雌球果发育中胚珠发育顺序及苞鳞数目等特征，认为福建柏属最原始，而圆柏属则较为进化，其它各属则介于上述两属之间。 江泽平和王豁然（19的）提出，柏木亚科和澳洲柏亚科的主要区别在于球果可育苞鳞的着生位置，如前者球果顶部苞鳞没有胚珠发育，而后者则是球果顶部苞鳞腋内有胚珠发育。这一观点显然与柏木属和圆柏属的多数雌球果顶部的苞鳞腋内有种子产生的情况不相符合。 依据本文的研究的结果及前人对柏科和相近类群的研究资料，赞同保留独立的柏科和杉科；另外，以往侧柏曾被置于崖柏属中，但依据其雌球果苞鳞中有倒转的维管束发育，崖柏属的崖柏和北美香柏雌球果的苞鳞中均无倒转的维管束发育，我们支持其独立为侧柏属。更多还原

【Abstract】 The female cone in conifer has received considerable attention not only for its systematic significance, but also for its intriguing morphological nature. In a series of detailed studies of fossil and living conifers, Florin (1954) came to the most widely accepted conclusion that the female cones of most conifers are compound structures, in which the seed scale represents a modified branch borne in the axil of a bract scale. Many researchers were in favor of that "in modern conifers, evolutionary advancement in the ovulate cone is shown by the various degrees of fusion between the ovuliferious scale and its subtending bract. Throughout the Pinaceae, the bract is only basally adnate to the scale, whereas these structures are more or less completely united in members of the Taxodiaceae and Cupressaceae."Female cone development in some conifer species was extensively investigated, most of which supported Florin’s theory. Nevertheless, the results were not consistent with the interpretation that the ovuliferious scale and bract were completely united in the female cone of Cupressaceae. The family Cupressaceae including about 20 genera, widely spread in the Northern and Southern hemispheres. As to such a large family, the relevant results derived from the limited species were not adequate for a conclusion. Therefore, it is essential to examine the female cone development in a wide range of species.Ontogeny and vascular system of female cones from 7 northern genera of Cupressaceae (Calocedrus, Chamaecyparis, Cupressus, Fokiena, Juniperus, Platycladus, Thuja) were investigated in detail by means of SEM together with conventional sectioning technique. The main results are briefly summarized as follows: 1) The bracts were arranged in the decussated manner similar to those in leaves.2) No, ovuliferous scale was observed in all of the species investigated.3) In the axil of the bract, the ovules were developed simultaneously or in acropetal order.4) In Juniperus and Cupressus, the uppermost pair of bracts were fertile or sterile. While in other genera the uppermost 1-2 pair(s) of bract were sterile.5) In Cupressus, which have global cone with large number of ovules, 2-3 series ovules initiated in a basipetal sequence in the axil of each bract6) Female cone development revealed the transition from several lateral ovules to the single terminal ovule in Juniperus.7) In all the genera studied, three types of vascular system in female cones could be recognized. (1) In Juniperus, Cupressus, Chamaecyparis and Fokiena with global cone and peltate scale, radial branching of the strands formed two vascular arcs: an adaxial series of strands with inverted orientation of the xylem and an abaxial system comprising normally oriented bundles. (2) In Calocedrus and Platycladus, only a single series of inverted vascular bundles were generated in the adaxial side of the bract scale; (3) There was no inverted vascular bundle developed in the bract scale of Thuja occidentals.The ontogeny of ovulate cone revealed that the female cone in Cupressaceae was a compound structure. In the axil of the fertile bract, the ovules were initiated on a broad swelling, which represented the aborted secondary branch system.No ovuliferious scale was developed in Cupressaceae, which indicating that the evolutionary trends of female cone in conifers may not be the progressive fusion between the ovuliferious scale and the bract. The absence of the ovuliferious scale in Cupressaceae and some genera in Taxodiaceae implied that the ovuliferious scale had been lost from some Taxodiaceae in evolution.Taking the evolutionary trends in the characteristics of female cone into account, Fokienia was considered as the most primitive genus, while Juniperus was regarded as the most advanced one in all the genera studied. The rest genera were considered to be intermediate between the two genera mentioned above.Based on the characteristics of female cone in Curessaceae, together with results derived from earlier investigations, we believed更多还原