Shedding light on autonomous endosperm development

This study provides a detailed embryological and histochemical analysis of seed development in Miconia crenata, an autonomous apomict, and its sexual congener M. tococa (Melastomataceae). Both species exhibit a nuclear endosperm that is only partially cellularized and is rapidly consumed by the developing embryo. For the first time in Melastomataceae, partial endosperm cellularization was confirmed. Histochemical tests revealed that nucellar cells accumulate polysaccharides, which are gradually mobilized during embryogenesis, indicating that the nucellus contributes nutritionally to embryo growth. In M. crenata, additional embryos can arise adventitiously from cells near the hypostasis. Our findings highlight that the reduced nutritional contribution of the endosperm, combined with the compensatory role of the nucellus, may facilitate the maintenance and evolution of autonomous apomixis in the family, a pattern also seen in Asteraceae. These results expand our understanding of reproductive strategies in angiosperms and the structural basis for autonomous seed development.