Ontogeny and Ultrastructure of Secretory Oil Cells in Magnolia grandiflora L.

The ontogeny and ultrastructure of secretory oil cells in the leaves of Magnolia grandiflora were studied with light microscopy, scanning electron microscopy, and transmission electron microscopy. Oil cells are initiated by anticlinal division in ground meristem cells throughout the leaf blade. The oil cell increases greatly in size, and oil fills a large central vacuole. Although both lysigenous development and a stalk or cupule attaching the oil sac to the wall have been reported for secretory oil cells, neither was found in oil cells of M. grandiflora. The suberin layer in the wall of these cells forms late in development, is part of a bipartite rather than a tripartite wall, and is not continuous within the oil cell.