草莓未减数配子形成的细胞学研究

Cytological Studies on Unreduced Gamete Formation of Strawberries (Fragaria)

以自然产生 2n配子的二倍体新疆草莓为材料 ,采用常规压片的方法 ,观察了 2n花粉形成的细胞学过程。结果表明 ,草莓 2n花粉的形成主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 ,即由正常的十字形改变为平行形和八字形 ,进而导致二分体和三分体的形成。每个二分体将产生 2个 2n花粉 ,每个三分体将产生 1个 2n花粉和 2个n花粉。此外 ,还发现有极少量的 4n花粉 ,可能是四分孢子粘连。

A diploid strawberry (Fragaria vesca L.), which can naturally produce unreduced gametes (2n pollen) and doubled unreduced gametes (4n pollen), was used to study the cytological mechanism of 2n and 4n gamete formation. The result showed that the formation of 2n gamete was mainly due to the abnormal orientation of spindles at metaphase Ⅱ. The normal orientation of two spindles at metaphase Ⅱ is perpendicular to each other, which leads to tetrad formation at the end of meiosis. Two kinds of abnormal orientation of metaphase Ⅱ spindles, i.e. parallel spindles and triangle spindles, were observed. Of the parallel spindles, the 4 group chromosomes were distributed to 2 poles and formed a dyad which formed two 2n pollen grains further. Of the triangle spindles, the 4 group chromosomes were distributed to 3 poles and formed a triad which formed one 2n pollen grain and two n pollen grains. In addition, a few very big pollen grains (4n pollen) which probably due to the fusion of the tetrad were found.