Abstract:

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.

Key words: Keteleeria fortunei, microsporogenesis, male gametophyte development, pollination