Figure 1.

Formation of double gametophytes and dyad meiotic products in tam. A, Normal-looking pollen grains in tam. B, Two pollen grains in one exine wall in tam. The two brightly fluorescent nuclei visible in the tricellular pollen grain correspond to the two sperm cells; the vegetative nucleus is out of the plane of focus. C, Wild-type (WT) tetrads, showing the characteristic tetrahedral arrangement of the four microspores enclosed in a callose wall. Usually one or two spores are out of focus. D, Dyads in tam. Note the callose wall. 4′,6-Diamidino-2-phenylindole (DAPI) staining was used. Scale bar, 10 μm.