Cellularization of the Free Nuclear Endosperm in Rice Caryopsis Revealed by Light and Electron Microscopy

Summary

Events during the early development of rice endosperm were studied cyto-histologically. Attempts were made to clarify the sequential changes during the early developmental stages of endosperm to reveal the ultrastructural details of the first-anticlinal wall formation and the subsequent cellularization. Early development of nuclear endosperm rapidly proceeded after anthesis and a large number of free nuclei proliferated until 48 HAA. In a large central cell, phragmoplasts arose as a result of alignment of vesicles appeared between the free nuclei located in the peripheral cytoplasm layer along nucellus. The phragmoplasts initially fused with wall of the nucellus and formed the initials of anticlinal wall. The initial wall grew toward a large central vacuole and reached tonoplast of central vacuole. Thereby, alveolar typed cell compartments ensued. Furthermore, the anticlinal wall continuously arose to form a large number of alveolar typed compartments. The cellularization of compartments including a free nucleus was achieved during 48 to 72 HAA. Microtubules and Golgi apparatus seemed to contribute to cellularization. Lastly, the process forming first-anticlinal wall is followed on a representative diagram and compared with the cellularization in other cereal endosperms.