Fig. 1. Wild-type, atk1-1 and revertant phenotypes. (A) A region of an atk1-1 plant with both mutant branch (arrow) and Ac-induced revertant sectors (arrowhead) that had normal siliques. (B) A wild-type flower. (C) An atk1-1 flower. (D) A wild-type tetrad with four microspores. (E) A product of atk1-1 meiosis, showing six microspores of unequal size. (F) Wild-type pollen grains of uniform size are brightly stained, indicating that they are functional. (G) atk1-1 pollen grains of variable sizes; most were faintly stained, indicating that they are dead. (H) Polar view of a wild-type pollen grain, with three apertures (arrows) that partition the pollen surface equally. (I) A side view of a wild-type pollen grain, showing the long apertures. (J) An atk1-1 pollen grain, showing that three apertures (arrows) were located unevenly on the pollen surface. (K) An atk1-1 pollen grain, showing that the apertures (arrows) were shorter than those of the wild-type pollen. Scale bars: 0.5 cm in A; 0.5 mm in B,C; 25 µm in D-G; 10 µm in H-K.