Megasporogenesis and microsporogenesis in Vicia faba

Abstract

A multicellular archesporium develops beneath two layers of cells in the young ovules of Vicia faba L. The megaspore mother cell differentiates from the apical cell of this archesporial group. A linear array of megaspores results from a normal meiosis. The inner integument is initiated by periclinal divisions in a ring of two ovule epidermal cells while the outer integument arises as a bump at the base of the ovule. Integument development starts while the megaspore mother cell is in early prophase I. The megaspore second from the chalazal end is the functional megaspore. In the anthers, meiosis in the microsporocytes is initiated before meiosis in the megaspore mother cells and follows the classic pattern. The tapetum becomes progressively more distinct during early prophase I. The nuclei complete several DNA replications without dividing. The tapetum finally disintegrates after the uninucleate microspore goes through mitosis. Endothecium development is apparent accompanying the elongation of the newly formed isodiametric microspores, as is the formation of the complex spore wall architecture.