Electron micrographs showing ultrastructures of cotyledon cells of germinatedV. mungo seeds (A-G), immunogold localization of α-amylase in cotyledon cells (H), and ultrastructure of cells of detached cotyledons (I). Toluidine blue (TB) staining of sections from cotyledons of day 3 V. mungo seedlings. Conversion from TB-stained cells (region I) to TB-stainless cells (region III) was accompanied with that of the PSV to LV. (B) SGs and PSVs in TB-stained cells (A, region I). The PSV was filled with storage proteins. Arrowheads indicate border between SGs and the cytoplasm. (C) SGs and PSVs in cotyledons at region II in A. Electron density of PSVs became low. SGs were surrounded with membranous structure (arrows). LED areas were found between SGs and the cytoplasm. (D) SG and LV in TB-stainless cells (region III in A). The PSV was converted to the LV in the cells. The areas around SG with LED were enlarged. (E) Ultrastructure of TB- stainless cells. SGs wrapped with a LED area contacted with LVs (arrowheads). Vesicles with similar density to LVs were observed. (F) LED membranes around the SGs fused with the LV membranes (arrow). (G) SGs were observed in LVs. The shape of SGs were largely different from those in B-E. (H) An Immunogold image representing degradation of SGs by α-amylase localized in LVs. Gold particles from anti-α-amylase antibody were densely detected in the peripheral region of SGs, which is inserted into the inside of the LV. (I) PSVs were not converted to LVs, and SGs were not taken up into PSVs in the cells of detached cotyledons. Neither low density areas around SGs nor vesicles with similar density to LV was observed in the cells. LV, lytic vacuole; Mt, mitochondrion; PSV, protein storage vacuole; SG, starch granule. Bars: (A) 50 μm; (E and G) 2 μm; (D, F, and I) 1 μm; (B, C, and H) 200 nm. 