Embryo and endosperm development in ovules of Papaver nudicaule after in vitro placental pollination

Abstract

Embryo development in Papaver nudicaule L. following in vitro placental pollination is of the Solanad type. Nuclear endosperm develops within 2–3 days and a filamentous proembryo is established. Endosperm cellularization is underway at the time the embryo proper begins to differentiate from the terminal and subterminal cells of the proembryo. After 6 days, the highly vacuolate endosperm is completely cellular; there is also a small globular embryo with no apparent endosperm degradation. Endosperm breakdown is initiated at the embryo–endosperm interface between 8 and 9 days postpollination. At day 10 of incubation, endosperm cytoplasm is dense and there is a large globular embryo. Substantial crenulation of the outer tangential wall of the protoderm occurs at this time. This phenomenon is presumably related to aspects of endosperm degradation. The primary tissue systems are discernable between 12 and 15 days when cotyledon initiation occurs. Seed development is complete within 27–28 days after placental pollination and the majority of the seeds germinate. This experimental approach provides a useful system for the study of a number of factors influencing seed ontogeny.