Fig. 5.

Symplasmic domains during SE in 35S:BBM seedling explants are characterized by a higher SEL than IZE explants. (A) The surface of a 4-day-old 35S:BBM seedling cotyledon showing HPTS fluorescence inside the cells (c, cytoplasm; arrow shows absence of the fluorochrome in the cell wall, indicating that its moves between cells through PD). The inset is a lower magnification of the seedling cotyledon (cot). The arrow points to an embryogenic protrusion. (B) F-dextran of 3 kDa applied to the cotyledon margin cells after 4 d of culture (arrow) does not move into other regions of the explant (inset, higher magnification). (C) After 7 d of culture F-dextran fluorescence is visible in the cotyledon margin cells, with the exception of a small group of cells forming an embryogenic protrusion (black dotted line). The arrows mark the site of F-dextran application. Scale bars: (A) 20 µm; (A inset, B, C inset) 100 µm; (B inset) 50 µm; (C) 200 µm.