【摘要】 用能自然产生２ｎ配子的二倍体大白菜ＢＰ０５８为材料，研究了２ｎ雄配子发生的细胞学机制。结果表明，大白菜２ｎ雄配子的形成上要是由于减数分裂过程中，中期Ⅱ两个纺锤体的定向发生改变所致，即由正常的相互垂直定向改变为八字形和平行形定向。在后期Ⅱ八字形定向纺锤体将分离的４组染色体分到三极，导致再组核和三分体的形成。每个三分体将产生２个ｎ配子和１个２ｎ配子。这是大白菜２ｎ雄配子发生的主要途径和突出特点。中期Ⅱ纺锤体平行定向的细胞较少，并且观察发现只有两个平行纺锤体并合在一起才能导致二分体的形成。每个二分体将产生２个２ｎ配子。更多还原

【Abstract】 A diploid Chinese cabbage variety--BP058 which can produce 2n gametes with high frequency naturally was used to study the cytological mechanism of 2n gamete formation. The results showed that the formation of 2n gametes was mainly due to the abnormal orientation of metaphase Ⅱ spindles of meiosis. The normal orientation of two spindles at metaphase is Perpendicular to each other, which leads to tetrad formation at the end of meiosis. Two kinds of abnormal orientation of metaphase spindles, i. e. triangle spindles and parallel spindles, are observed. Triangle spindle orientation at metaphase of microsporogenesis leads to nuclear restitute at one pole and formation of triads instead of tetrads. Each of triads will produce one 2n pollen. This is the main way for Chinese cabbage to produce 2n gametes. As compared with triangle spindles, the parallel spindles are quite few and only those parallel spindles closed or fused to each other are associated with nuclear restitution and dyad formation. The 2n gametes produced through the machenisms as above indicated genetically maintain the genie composition of their mother cells. 2n pollen is much bigger than n pollen and its vitality is no obvious difference from that of n pollen.更多还原