Ultrastructure of Megasporogenesis in Facultative Apomictic Monosonic Addi-tion Line M14 of <I>Beta corolliflora</I> of Sugar Beet

Abstract

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 em-bryo-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 vacu- oles,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 rec- reation of M14.Ultrastructure observation on M14 showed the signs of diploid apomictic recreation:no meiosis,no nuclear vacu- oles,no cytoplasmic components differentiation,no callose deposition,and no plasmodesmata.