The Atmnd1 mutant shows sterility. (A,D,F,H,I,J,K) Wild-type, (B,C,E,G,L,M,N,O) Atmnd1. (A) Wild-type Arabidopsis with elongated siliques. (B) Sterile Atmnd1 plant with non-elongated siliques. (C) Mutant plant transformed with a wild-type AtMND1 gene displaying restoration of fertility. (D) Wild-type flower. (E) Mutant flower showing under-developed stamen and stigma devoid of pollen grains. (F) Cleared anther containing round and uniformly sized pollen grains. (G) Mutant anther containing shriveled pollen grains. (H) Stage 2–4 ovule displaying the megaspore mother cell (MMC). (I,L) Stage 3-1 ovule showing the functional megaspore (J) Cleared wild type mature embryo sac; a, antipodals; c, central cell; e, egg cell. (K,O) Alexander staining for pollen viability; arrowhead indicates a rare purple viable pollen grain in the mutant. (M) Mature ovule with female gametophyte arrested at the uninucleate stage. (N) Mature ovule containing degenerating material instead of an embryo sac. Scale bars: K, O, 50 μm; H-J, L-N, 20 μm. Ovule stages are according to .