Absence of the Nucleolar Constriction in the Division of Generative Nucleus in the Pollen of Some Angiosperms

The morphological feature of the nucleolar constriction was studied in the chromosomes of generative nuclei in the following twelve species of Angiosperms: Narcissus jonquilla, Tradescantia paludosa, Brodiaea unfora, Hemerocallis thunbergii, Allium fistulosum, Impatiens balsamina, Lotus corniculatus, Pedicularis resupinata, Salix gracilistyla, Thea sinensis, Hordeum vulgare and Aster scaber. In all of the species studied, except for Allium fistulosum, the nucleolar constirction which is a structural characteristic of the nucleolar chromosomes of the respective species was found to be absent in the chromosomes of the generative nuclear division in pollens. The absence of the nucleolar constriction was confirmed by the observation of dinuclear and trinuclear pollens.