Defective pollen grains in the spf1-1 spf2-1 double mutant. A to D, Wild-type pollen grains. E to H, spf1-1 spf2-1 pollen grains. A and E, Pollen visualized by transmission microscopy after staining with Alexander’s reagent. B and F, DAPI-stained pollen (B1 and F1 for bright field and B2 and F2 for UV light). C and G, Pollen visualized by scanning electron microscopy (C1 and G1) and transmission electron microscopy (C2, G2, and G3), showing abnormal shape and contents in the double mutant compared with the wild-type. D and H, Pollen from wild-type (D) and double mutant (H) plants were artificially pollinated on wild-type stigmas, and the growth of pollen tubes was visualized by Aniline Blue staining, showing that the growth of pollen of the double mutant was obviously affected. Arrowheads, Abnormal pollen grains; thin arrows, uninucleate pollen grains; thick arrows, binucleate pollen grains. Bars = 20 μm for A, B, E, and F, 5 μm for C and G, and 400 μm for D and H.