The embryo sac development of Manfreda elongata (Asparagaceae)

摘要

Manfreda Salisb. belongs to the Asparagaceae family and is a genus of a high ornamental potential due to the beauty and varied morphology of its leaves, as well as it provides flowers of different species throughout the year. In spite of its economic relevance, little is known about its sexual reproduction. This work aimed to characterize the female gametophyte development of Manfreda elongata through a stain-clearing technique of whole ovules and then analyzed by confocal microscopy. The female gametophyte development of M. elongata is of the monosporic Polygonum-type. The megaspore mother cell of M. elongata contains a dense and prominent nucleus, and at megasporogenesis, when meiosis II is completed, linear and T-shaped tetrads of megaspores were observed. Of this, only the megaspore closest to the chalaza remains functional. In the process of megagametogenesis, three rounds of free nuclear mitosis produced an eight-nuclei embryo sac. At maturity, a sevencelled embryo sac is formed by an egg apparatus (egg cell and two synergids) at the micropylar end, a central cell (with a diploid nucleus resulted from the fusion of the two polar nuclei). Thus, at the end of its formation, the female gametophyte development of M. elongata is of the monosporic, Polygonum-type.