【摘要】 研究了甜柿品种‘禅寺丸’2n花粉形成的细胞学机理 ,检测到导致 2n花粉形成的异常减数分裂现象 :(1)中期Ⅱ和后期Ⅱ的小孢子母细胞中发生异常的纺锤体定位 ,表现为平行 (ps)、融合 (fs)和三极纺锤体 (tps) ;(2 )末期Ⅱ4个子核呈两极分布 ,每极 2核 ,或呈三极分布 ,其中一极 2核 ,另两极单核 ;(3)四分体时期观察到二分体和三分体。二分体最终发育成 2个 2n配子 ,三分体则形成 1个 2n配子和 2个n配子。经二分体和三分体的发生频率估算出的2n花粉频率与当年以花粉直径为指标测得的 2n花粉的实际发生频率基本一致。因纺锤体定位异常而产生的 2n配子遗传上等同于FDR(第 1次分裂重组 )型 ,因而在有性多倍化中具有重要的利用价值。更多还原

【Abstract】 Cytological mechanisms of 2n pollen formation were studied in nonastringent persimmon ’Zenjimaru’ ( Diospyros kaki L.). The observed meiotic abnormalities resulting in the 2n pollen production revealed that: (1) disoriented spindles, including parallel, fused and tripolar spindles, were formed at metaphase II and anaphase II; (2) the nuclei at telophase II were arranged in two poles, each pole contained two nuclei, or in three poles, one of which contained two nuclei, the other two contained one nucleus respectively; (3) dyads and triads were produced at the tetrad stage. The dyad would develop into two 2n pollens, and the triad would develop into one 2n and two n pollens. The frequency of 2n pollen production predicted by frequencies of dyads and triads agreed with that estimated by pollen diameters. The 2n pollens produced by this mechanism were genetically equivalent to FDR (first division restitution) gametes, and consequently had a potential value for sexual polyploidization.更多还原