甜菜无融合生殖单体附加系M14大孢子发生的超微结构

应用透射电镜技术探求甜菜单体附加系M14 (Beta vulgaris L.,VV+1C, 2n=18+1)有性生殖大孢子与二倍体孢子生殖大孢子发生时的超微结构特征,了解有性生殖和无融合生殖起始细胞的超微结构差别。甜菜单体附加系M14为兼性无融合生殖体,大孢子发生有韭型、蝶须型和蓼型三种类型。韭型和蓼型大孢子发生时均起源于大孢子母细胞,二分体之前从形态结构上难以区分;减数分裂前期I,细胞核中出现核液泡,形成联会复合体,细胞质改组,细胞壁上沉积胼胝质。韭型大孢子发生时,只进行减数第一次分裂,不发生减数第二次分裂,形成二分体,珠孔端二分体细胞退化,合点端二分体细胞发育为二倍体功能大孢子。蓼型二分体的珠孔端细胞在减数第二次分裂前或分裂过程中退化,合点端细胞经减数第二次分裂形成两个细胞,构成三分体,最终合点端大孢子发育为单倍体功能大孢子。蝶须型大孢子发生是M14中唯一的二倍体孢子无融合生殖方式,其大孢子发生时大孢子母细胞不发生减数分裂,不出现核液泡,未形成联会复合体,无细胞质改组,细胞壁上缺乏胼胝质的沉积和缺乏胞间连丝,这些可作为二倍体孢子无融合生殖的鉴定指标。

Ultrastructure of Megasporogenesis in Facultative Apomictic Monosonic Addition Line M14 of Beta corolliflora of Sugar Beet

Research on ultrastructure of megasporogenesis facultative apomictic monosonic addition line M14 of Beta corolliflora of sugar beet by TEM, in order to get the distinctions between the initial cells of sexual reproduction and apomixes. The embryo-sac development of M14 can be classified into three types: Allium odorum-type, Antennaria-type, and Polygonum-type. There was little difference between Allium odorum-type and Polygonum-type until the stage of dyads. At meiosis I, nuclear vacuoles, synaptonemal complexes showed up, cytoplasmic components underwent differentiation, callose deposited in the wall. The megasporocyte of Allium odorum-type only underwent meiosis I to form a dyad, and then the micropylar dyad cell of Allium odorum-type degenerated quickly, while the chalazal one developed into diploid functional megaspore. In Polygonum-type the micropylar dyad cell degenerated quickly, while the chalazal one finished meiosis II to form two unequal-sized megaspore. The megaspore at chalazal end developed into haploid functional megaspore. Antennaria-type was the only fashion of apomictic recreation of M14. Ultrastructure observation on M14 showed the signs of diploid apomictic recreation: no meiosis, no nuclear vacuoles, no cytoplasmic components differentiation, no callose deposition, and no plasmodesmata.