油杉花粉个体发育与传粉过程

应用常规压片法和整体染色透明法对油杉小孢子的发生和雄配子体的发育过程进行观察,研究其传粉生物学特征.结果表明:油杉小孢子母细胞在1月26日-2月5日进行减数分裂,在减数分裂过程中胞质分裂为同时型,四分体排列方式多为左右对称型;小孢子经过连续4次有丝分裂后,于2月底形成5-细胞型的成熟花粉粒,成熟花粉由两个原叶细胞、一个不育细胞、一个精原细胞和一个管细胞组成,其中两个原叶细胞在花粉成熟时已退化;经TCC法检验,花粉生活力为92.6%;3月1日-8日为油杉传粉期,3日-5日为传粉高峰;在传粉期间,胚珠珠孔端无传粉滴产生,珠孔端耳状结构边缘粘附有花粉.虽然花粉母细胞发育表现出不同步现象,产生少数具3个或4个气囊的异形花粉,但从小孢子的发生及雄配子体发育的整个过程看,未见败育或其他异常现象,能形成大量正常的成熟花粉,因此,花粉个体发育不是影响油杉结籽率低的主要因素,而造成油杉球果结籽率低的主要原因可能在于其传粉过程.

Ontogeny of Pollen and Pollination in Keteleeria fortunei

In order to find the causes for the low seed set rate in Keteleeria fortunei, which is vulnerable endemic species to China, the microsporogenesis, the development of male gametophyte were investigated by means of the normal slice_making method and the whole stain_clearing technique, and the biological characteristics of pollination was also studied preliminarily. The results showed that the meiosis of microspore mother cells (MMC) took place from Jan.26 to Feb. 5, 2003. The meiotic cytokinesis of MMC was simultaneous, and tetrads were mainly isobilateral. After four times continuous mitosis of microspore, mature pollen grain was formed in later Feb.. Mature pollen grain was 5_celled, comprising two prothallial cells, a sterile cell, a spermatogenous cell and a tube cell. The TCC stain test showed the average vitality rate of mature pollen grains was 92.6%. The pollination occurred in early Mar. and lasted about 8 days with a dominant peak from Mar.3 to Mar.5. During pollination period, no pollination drop was found on the ovule. The mature pollen grains were captured on the edge of the ear_like structure at the extremity of the micropyle. Though the development of MMC was not synchronous and small number of abnormal pollen grains having three or four air sacs could be found in the mature microsporangium, the microsporogenesis and the male gametophyte development were normal on the whole, producing a great number of normal pollen grains. Abortion phenomenon also was not observed in the microsporangium. Therefore, it is unlikely that the development of pollen was an important factor for the low seed set rate. The key factor that causes the low seed set rate may be relative to the pollination biology. It was believed that environment conditions could exert strong influence on the pollination. This study provided not only the scientific basis for setting up the effective conservation methods and improving forestry production of Keteleeria fortunei, but also a significant embryological characteristics for the systematic classification of Keteleeria.