Figure 4.

Female gametophyte and seed development in wild-type and ctf7^+/2 siliques. The images represent a single 1.5-μm optical section unless otherwise noted. A to D, Normal ovules. E to L, ctf7 ovules. A, Wild-type female gametophyte at stage FG7 containing two synergid cells (SN), an egg cell (E), and a central cell (CC). A projection of three 1.5-μm optical sections is shown. B, Female gametophyte at stage FG8 with degenerated synergid cell (DS). A projection of three 1.5-μm optical sections is shown. C, Fertilized developing seed that contains an elongated zygote (ZN) and two endosperm nuclei (EN). A projection of two 1.5-μm optical sections is shown. D, Developing seed in which the zygote has formed the suspensor (S) and terminal (T) cells. E, First optical section of an ovule with three undegenerated antipodal cells. A degenerated synergid cell, a persistent synergid cell, and the egg cell are at the micropylar pole. One of the three antipodal cells (AN) is at the bottom of the embryo sac. F, Second optical section showing two antipodal cells at the bottom of the embryo sac. G, Third optical section with the central cell in the middle of the embryo sac. H, Fertilized seed containing degenerated and persistent synergid cells and a zygote (Z). The endosperm nucleus has divided into two nuclei (EN). A projection of three 3-μm optical sections is shown. I, Optical section (3 μm) through the chalazal pole of the same seed in H. The nucleus and cell membrane of three antipodal cell nuclei are still intact. J, ctf7 seed containing a degenerated zygote (DZ) and eight endosperm nuclei. Only one of the endosperm nuclei is in the same section as the zygote. K, ctf7 seed containing a degenerated zygote and 16 endosperm nuclei. Five of the endosperm nuclei are observed. A projection of three 1.5-μm optical sections is shown. L, Degenerated ctf7 seed containing degenerated zygote and degenerated endosperm (DE) nuclei. A projection of two 1.5-μm optical sections is shown. Bars = 10 μm.