Figure 3

Stages of ovule development in H3 (A-F) and S1 (a-f). Photomicrographs of chloral hydrate cleared ovules. (A, a) MMC has differentiated (arrow) and inner integument has initiated. (B, b) Megaspore tetrad has been produced (arrow) but outer integument primordia form only in H3. (C, c) Postmeiotic ovules. The arrows indicate degenerated haploid spores in S1. In H3 the integuments extend to nucellus, whereas, integument arrests at initiative stage in S1. (D, E, F) Mononuclear, two-nuclear and mature embryo sacs of H3, respectively. (d, e, f) S1 ovules at the same stage as normal mature embryo sac but abnormal nucellus without integument surrounding: one nucleus (arrows) and three degenerated spores (arrowheads) in d, two nuclei (arrows) and a ray of residuum (arrowheads) in e, one small nucleus likely without differentiation (arrow) in f. MMC: Megaspore Mother Cell. Bar = 20 μm in A-B, a-b and 50 μm in C-F, c-f.