Figure 4.

Starch accumulation in leaf cell types.

(A) Light micrograph of a transverse section of a leaf harvested at the end of the light phase. The upper epidermis is on top. Epidermal cell (Ep), mesophyll cell (Me), bundle sheath cell (BS) and guard cell (GC). Scale bar = 20 µm. The leaf section was embedded for electron microscopy as described in Streb et al. (2008), and lightly stained with toluidine blue (at 20°C for 20 min). B-I. Transmission electron micrographs of cells from leaves harvested at the end of the day (B to E) and the end of the night (F to I). Scale bars = 1 µm. At the end of the night only guard cell plastids contain starch. B and F. Epidermal cell plastids. C and G. Mesophyll cell chloroplasts. D and H. Bundle sheath chloroplasts. E and I. Guard cell chloroplasts.