三棱栎属分类的孢粉学证据

PALYNOLOGICAL EVIDENCE FOR TAXONOMY OF TRIGONOBALANUS (FAGACEAE)

壳斗科三棱栎属ＴｒｉｇｏｎｏｂａｌａｎｕｓＦｏｒｍａｎ含３种，即：三棱栎Ｔ．ｄｏｉｃｈａｎｇｅｎｓｉｓ，南美三棱栎Ｔ．ｅｘｃｅｌｓａ，轮叶三棱栎Ｔ．ｖｅｒｔｉｃｉｌａｔａ。通过用光学显微镜、扫描电子显微镜、激光共聚焦显微系统及透射电子显微镜对３个种的花粉进行观察并比较分析，确认它们分别属于显然不同的３个类型：（Ａ）花粉粒为扁球形，赤道面观宽椭圆形，极面观钝三角形；孔在角上，内孔具明显的孔室，孔缘加厚；外壁覆盖层无穿孔，孔区外壁２（从化学分层）特厚；表面具疣波状纹饰。三棱栎为此类型。（Ｂ）花粉粒为长球形，赤道面观长椭圆形，极面观近三角形或三瓣形；萌发孔多为３拟孔沟（３沟），位于三角形的边上；外壁覆盖层具穿孔，表面具粗瘤（疣）状纹饰。南美三棱栎为此类型。（Ｃ）花粉粒近球形、赤道面观近圆形，极面观３裂圆形，３孔沟在边上；覆盖层具穿孔；表面具小瘤和蠕虫状短条纹饰。轮叶三棱栎为此类型。以上３个种的花粉粒形状、萌发孔、外壁结构、表面纹饰等特征，特别是萌发孔特征、类型及位置，在壳斗科的花粉形态中表现出较大差异，越出了种间的区别，故笔者认为Ｋ．Ｃ．Ｎｉｘｏｎ和Ｗ．Ｌ．Ｃｒｅｐｅｔ将３个种分立为３个单型属是自然合理的，即?

The genus Trigonobalanus consists of three species which are disjunctly distributed in Asia and South America. Pollen grains of T. doichangensis(Camus) Forman, T. verticillata Forman and T. excelsa G. Lozano, J. HdzC. et J. Henao were examined under light microscope (LM), scanning electron microscope(SEM), laser scanning confocal imagine system(MRC600) and transmission electron microscope(TEM). Pollen morphology of these species of Trigonobalanus showed great variation in shape, aperture position and structure of exine. The pollen morphology of Trigonobalanus may be divided into three types: (A)Pollen grains of T. doichangensis are suboblate, with P/E=0.88～0.96, broad elliptic in equatorial view, obtusely triangular in polar view; 3colporate, goniotreme, vestibulate and thickened on margin; the exine 2layered, the thickest in aperture area, tectateimperforate, verrucoserugulose (SEM). (B) Pollen grains of T. excelsa are prolate, with P/E=1.23～1.55, longelliptic in equatorial view, trilobate or subtriangular in polar view; 3colporoidate (3colpate), pleurotreme (pretrime); tectateperforate, crasstuberculate or verrucose (SEM). (C) Pollen grains of T. verticillata are subsphaeroidal with P/E=1.10～1.18, subcircular in equatorial view, trilobatecircular in polar view; 3colporate, pleurotrime; tectateperforate, finetuberculate or vermiculate shortstriate(SEM).The pollen morphology of the three species of Trigonobalanus well supports the viewpoint of Nixin and Crepet to treat them as three monotypic genera, i.e. Formanodendren (F. doichangensis(Camus) Nixon et Crepet), Colombobalanus (C. excelsa(G. Lozano, J. HdzC. et J. Henao)Nixon et Crepet) and Trigonobalanus (T. verticillata Forman). The results also show that the three genera are closely related to Fagus and Quercus.