热激或低温诱导辣椒产生2n花粉的细胞遗传学机理

Cytogenetic Mechanism of 2n Pollen Formation Induced with Heat-shock or Low Temperature in Capsicum Annuum L.

通过检查小孢子母细胞减数分裂染色体行为和四分孢子行为,分析了热激或低温诱导产生2n花粉的细胞遗传学机理。减数分裂细线期——偶线期的母细胞经过热激或低温处理,联会复合体的形成受到抑制,形成FDR重组核,产生未经交换或少交换的FDR 2n花粉。热激或低温处理影响联会复合体的稳定性,开始处理时处于减数分裂粗线期——终变期的母细胞中,观察到二价体提前解体,部分母细胞发生第1次分裂核重组,产生已经交换的FDR 2n花粉。热激、低温还能使处于减数分裂后期Ⅰ——中期Ⅱ的母细胞产生异常,一是后期Ⅱ出现落后染色体,造成部分细胞第2次分裂核重组,产生SDR 2n花粉;再是减数分裂的细胞质异常分裂,四分体时期产生双核二分体,但不能明确这种二分体发育成的2n花粉属于FDR型还是SDR型。

The cytogenetic mechanism of 2n pollen formation after heat-shock or low temperature treatment was determined on the basis of the behavior of meiotic chromosomes and sporads during microsporogenesis. The formation of synaptic complex was partially or even entirely inhibited in meiotic cells treated with low temperature or heat shock during meiotic leptotene to zygotene, which would lead to first division restitution of nuclei and the occurrence of none cross over 2n pollen. The stability of synaptic complex was affected either by heat shock or by low temperature treatment applied to male meiotic cells during pachytene to diakinesis, which resulted in disaggregation of bivalents, restitution of nuclei in part of cells, and formation of cross over 2n pollen. Cells at meiotic anaphase I - metaphase II also responded to the treatments. One of the two cytological phenomena observed was the laggards at anaphase I which led to second division restituted nuclei and SDR 2n pollen. Another phenomenon was the abnormal cytokinesis and the subsequent binucleate dyad, but no evidence sufficient to determine unambiguously the 2n pollen developed from binucleate dyads equivalent to FDR or SDR type.