Electron Microscope Observations of the Lipid Globules and Vacuolar Granules in the Mesophyll Cells of Rice Plants

The lipid globules and vacuolar granules in the mesophyll cells of ricc plants were observed by electron microscope at intervals of 10 days after leaf expansion. When the leaves had just fully expanded, many small lipid globules appear in the cytoplasm around nucleus, and afterwards they coalesce into one or several larger globules. After leaf expansion the lipid globules rapidly increase in diameter, but with the progress of leaf senescence the rate of increase gradually becomes slower and the diameter reach above 5 μm. The lipid globules remain in the dead leaf without remarkable destruction. On the other hand, soon after leaf expansion the electron dense granules appear in the vacuoles of mesophyll cell and increase in diameter by adhesion of the flocculent particles. The electron micrographs of the vacuolar granules show a spherical, rough-surfaced structure. Both the granules and flocculent particles in vacuole probably consist of protein. Increasing process in diameter of the vacuolar granules is the same as the lipid globules. As the leaf color changes to yellow, the vacuolar granules decrease in electron density and in the yellow leaf the disintegrating granules are observed.