SLK1 and SLK2 are required with ANT and SEU for ovule initiation from the CMM. A, Col-0 flower. B, Morphology of a slk1 slk2 mutant flower is near that of Col-0. C, ant mutant. D, Gynoecial disruptions are enhanced in slk1 ant slk2 triple mutant relative to the ant and slk1 slk2 mutants. E and F, More severe reductions of CMM-derived tissues are observed in seu/+ slk1 ant slk2 (F) relative to the seu/+ slk1 ant slk2/+ (E) genotype. G to L, Scanning electron micrographs of flowers from the indicated genotypes. In I, the arrow indicates the basal valve boundary. In K, the seu/+ slk1 ant slk2 genotype conditions complete loss of ovule primordia and severe reduction of CMM-derived tissues (arrowhead). L shows a stage 10 flower. Disruption of the CMM is already evident at this stage. M to P, Optical cross sections from cleared gynoecia of the indicated genotypes. Arrowheads in P indicate the few ovules that have initiated. Bars = 1 mm in A to K, 100 μm in L, and 0.5 mm in M to P. [See online article for color version of this figure.]