江南桤木(Alnustrabeculosa)的花粉形态与其生态因子

STUDY ON POLLEN MORPHOLOGY AND ECOLOGICAL FACTORS OF ALNUS TRABECULOSA

采用光学显微镜、扫描电镜和透射电镜对产自安徽省岳西县鹞落坪国家自然保护区的桦木科江南桤木的花粉形态进行了观察和研究。结果表明花粉粒圆球形至近球形,花粉大小为22.5—35.0μm,平均为31.5μm。赤道面观近扁球形,极面观为四角形或五角形。光学显微镜下,4-5孔,孔的结构特殊,内、外层到孔边分离,形成显著的孔室。在光切面看,外层在孔处加厚,孔间带状加厚。同时,在扫描电镜下,萌发孔沿赤道排列,为短萌发孔,萌发孔长轴3.2μm,短轴为1.5μm,其长轴约为短轴的2倍。外壁厚为2.0μm,外壁外层明显厚于内层。外壁纹饰在光学显微镜为不明显的颗粒排列为细条纹,扫描电镜下为微刺。在透射电镜下,花粉壁分为明显的四层,即:覆盖层、柱状层、基层和内层;覆盖层有刺状纹饰等。同时研究了江南桤木花粉的地理分布及其与生态因子的关系。根据江南桤木植物赖以生存的生态因子,得出江南桤木花粉分布区的主要生态因子,包括地理位置、海拔高度、年降水量、年积温及生境,为利用地层中桦木科化石花粉重建古气候、古环境及气候变迁提供了现代孢粉学资料和依据,也为该植物的现代地理分布提供了科学依据。

Pollen grains of Alnus trabeculosa Hand-Mazz. from the Yaoluoping National Resources Reserve were examined by light microscope （LM）, scanning electron microscope（SEM） and transmission electron microscope（TEM）. The pollen grains are 4 5 porate, spheroidal or subspheroidal, equatorial view suboblate, polar view quadrilateral or pentagonal in shape, 22.5 35.0 μm in diameter. Under the LM, there are four or five apertures of special configu ration： the sexine and nexine are separated and form remarkable vestibulum. Uunder the optical section view, nexine thickens in the apertural region. The ornamentation of the exine is unconspicuous granule forming lirae. Under the SEM. the apertures are of short type, with the long axis of 3. 2μm in length and the short one 1.5 t^m. Exine is 2.0μm thick. The ornamentation of the exine is spinulose. Under the TEM, the pollen grains have the exine stratifi cation typical of the dicots： rectum, columellae, foot layer and endexine. Additionally. the connection between the geographis distribution and ecological factors of the pollen of Alnus trabeculosa is also studied in this paper. The main ecological factors of the pollen of Alnus trabeculosa are obtained in the Yaoluoping National Resources Reserve, inclu- ding geographical position, altitude, annual precipitation, annual accumulated temperature and habitat. On thc basis of these information, the climate and environment conditions of the Alnus trabeculosa are analysed, which is significant for estimating the palaeovegetation, palaeoclimate, paleaoenvironment and climate change by utilizing the fossil pollen of the Betulaceae.