Fig. 1. Wild-type and cytokinesis-defective guard cells. (A-C) Stoma-specific expression of KAT1-GUS, a marker for guard cell identity (Nakamura et al., 1995), in the cotyledons of 5-day-old seedlings germinated in the absence (A) or presence (B,C) of 5 mM caffeine, an inhibitor of cell plate membrane consolidation. scd1-1 mutant guard cells phenocopy the effects of caffeine. (D-F) Light microscopy of Toluidine Blue-stained scd1-1 leaf epidermis from plants grown at 22°C. (G,H) KAT1-GUS was expressed in cytokinesis-defective scd1-1 guard cells. Hanging pores are indicated by arrows. A torus and oblate type guard cell are shown in F and H, respectively. Scale bars: 10 µm.