Heterogeneity of GFP fluorescence in BY-2 calli and suspension cultures. (a) Primary calli obtained after transformation, showing calli with homogeneous and heterogeneous GFP expression either in mosaic or sectorial arrangements of cell populations with distinct GFP fluorescence. (b) Non-homogenous GFP expression in suspension cells. The arrows indicate cells with evidently different GFP expressions located in a single file. Scale bars: 1 mm for A, 50 μm for B.