Abstract: The influence of high temperature (33℃) on embryogenesis in isolated microspore culture of Chinese cabbage (Brassica campestris spp. pekinensis ) was investigated by microscpopy of FDA and DAPI. The microspores cultured at constant temperature of 25 ℃ lost their viability quickly and only few viable microspores were found after 7 days of culture. The morphology of the cultured microspores became as turgescent as the "rugby" which was similar to the mature pollen of the Chinese cabbage. The first nuclear division of the microspores was asymmetric. The microspores lost their capacity of embryogenesis under such condition. In contrast, when the microspores were cultured at 33℃ for 24 h before they were transfered to the culture condition of 25 ℃, their developmental pattern was changed. Some of the microspores could remain viable even for 7 days in culture, they became rounded off. The symmetric nuclear division pattern was induced. The frequency of such division was about 40%. Of the several new cell division types observed, the symmetric type was more frequent (55%) than others. The microspores treated under 33℃ were able to form embryoids via embryogenesis. The critical period of high temperature treatment on microspore culture of Chinese cabbage was about the initial 12 h, if the cell division index of microspore was concerned, but the period was the initial 24 h if the frequency of embryogenesis was considered.

Key words: Chinese cabbage, Microspore, Viability, Embryogenesis, Critical period of high temperature