矮牡丹小孢子母细胞减数分裂异常现象的观察

矮牡丹(Paeonia suffruticosa subsp. spontanea)(永济居群)存在多种结构杂合现象,减数分裂存在一些异常:如单价体、异形二价体、互锁四价体、六价体、后期I倒位桥、落后单价体、不均等分离、后期Ⅱ桥和微核等。统计了这些异常现象出现的频率,并对其形成的机制和对正常小孢子形成的影响进行了讨论。从细胞学水平上探讨了矮牡丹可能的濒危机制。同时结合前人的研究,对芍药属内3个组的结构杂合程度进行了比较。

OBSERVATIONS ON ABNORMAL MEIOSIS OF POLLEN MOTHER CELLS IN PAEONIA SUFFRUTICOSA SUBSP. SPONTANEA

Paeonia suffruticosa subsp. spontanea presents a variety of structural heterozygosity. Some abnormalities in meiosis of pollen mother cell (PMC) were observed in one variety of the natural population from Yongji County, Shanxi Province. Abnormalities observed are as follows: (1) Univalents. They were caused by failure in pairing, asynapsis and precocious cancellation of terminal chiasma. Oriented univalent pair was distributed at two poles normally in A I , while non-oriented univalent pair only at one pole. Another factor leading to univalents was that chromosomes were paired but without substantial exchange. The number and ratio of three kinds of chromosomes and their univalents were analysed and the result disagreed with that of Haga and Ogata. (2) Het-eromorphic bivalents. A few cells were observed with unequal E bivalents. Segements of the short arm of one E chromosome might be deleted or else be involved in translocation. (3) Bivalent interlocking . A few cells were found with two or three bivalents interlocked, which might cause translocation . (4) A I and A II bridges. There were three kinds of bridges in A I and A II ; they were one single chromatid bridge, two single chromatid bridges and double bridge. The ratio of these three kinds of bridges was 11.8%, 1.5% and 0.19% respectively. Bridges at A II occurred as continuity of those of A I owing to simultaneous development of microspores. Some bridges without fragments are also discussed. (5) There were 1.69% A I cells with abnormal disjunction of bivalents, which were caused by nondisjunct bivalents pulled to one pole and non-oriented univalent pair moving to one pole. (6) A few cells were found with lagged univalents and micronucli at A I , A II and T II , some fragments could be observed at A I and M II . The relationship between abnormalities in meiosis of PMC and somatic karyotype and pollen sterility are discussed. It is concluded that aborted pollen grains and ovules, space limitation in carpellum and low germination rate of seeds in natural populations are the main causes leading to endangerous status of this species-P. suffniticosa subsp. spontanea, the hetenwygosity degree of Sect. Mudan is lower than that of the other two sections.