Abnormal meiosis of pollen mother cells of larix leptolepis related to low temperature in late winter

Meiosis of pollen mother cells (PMC) in Larix leptolepis was studied from late January to early April to estimate the frequency of abnormality. PMC overwintered at diplotene stage and resumed activities in late February in Suweon area. Early separation chromosomes were observed in metaphase I and metaphase II, with frequency of 22.4% and 8.1% respectively. Lagging chromosomes and chromosome bridges were detected in anaphase I and anaphase II. Abnormal frequency (lagging chromosomes and chromosome bridges combined) was 19.9% in anaphase I and 3.3% in anaphase II. During formation of pollen sporads, duds, triads, and pentads were observed in addition to the normal tetrads, with the abnormal frequency of 15.8%. Metaphase I appeared to be most sensitive to low temperature, judged by highest frequency of abnormality. Assuming abnormal frequencies at five stages of development mentioned above were additive, abnormal frequency during teh entire meiosis of PMC reached 69.5% in Suweon area. Trees in Myeongjugun which was located in about 600m above sea level with colder climate showed similar abnormal frequency at each stage of meiosis, with a total abnormal frequency of 71.3%