Figure 6.

Salt stress derailed gametophyte development. Ovules from healthy (A–C) and stressed (D and E) plants were marked at stage 2-IV, and ovule development was monitored as a function of time. In terms of developmental time, the stressed ovules shown in D and E correspond to similar developmental times for the healthy ovules shown in B and C, respectively. A, In an ovule at stage 2-IV, the megaspore mother cell (mmc) occupies the central region of the nucellus. B, One day later, the megaspore mother cell went through meiosis, yielding one large haploid megaspore (m). C, This megaspore underwent three rounds of mitotic division and the products differentiated into a gametophyte. Within the gametophyte, the egg cell (ec), two synergid cells (sc), two central cells (cc), and three antipodal cells (ac) were present. D, When ovules were stressed at stage 2-IV, they completed meiosis, although the outer integument (oi) and inner integument (ii) grew more slowly than healthy ovules. E, The megaspore from this stressed plant went through only one mitotic division, yielding a gametophyte (g) with just two nuclei.