PMC

Scanning electron microscope micrographs of wild-type (A) and fdl1-1 mutant (B–F) germinating seedlings. (A) The first leaf emerges from the aperture at the top of a wild-type coleoptile. (B) A mutant coleoptile exhibiting a long subapical cleft. (C) A mutant coleoptile fractured by forcing leaves. (D) Leaves slipping laterally from the broken coleoptile; the leaf apical region is inside the closed top of the coleoptile. (E) An emerged leaf still joined with the coleoptile top. (F) A thick and greatly malformed mutant coleoptile. co, coleoptile; lf, leaf. Bars, 2mm.

The error bar represents the standard error of the mean. Number of lines in each coleoptile length class (n) is given above each bar. The horizontal line represents the mean in each coleoptile class (D–F).

Anatomy of coleoptile and embryo during submerged germination below a normoxic atmosphere. (A–D) The coleoptile tip was underwater. (E–H) The coleoptile tip was above water, but seminal roots have not yet emerged. (I,J) The coleoptile tip was above water and after seminal root emergence. Cross-sections of the coleoptile at the 5 mm from the embryo (B,F,J). Cross-sections of the embryo (C,D,G,H). Col, coleoptile; CO, coleorhiza; Emb, embryo; End, endosperm; Hol, hollow; L₁, 1st leaf; L₂, 2nd leaf; SR, seminal root; VB, vascular bundles. Scale bars: 5 mm in (A,E,I); 100 μm in (B,F,J); 500 μm in (C,D,G,H).

Scanning electron microscope (A, B) and light microscope (C–F) micrographs of the shoot region of 18 DAP embryos. (A) A wild-type embryo with the coleoptile enveloped by the scutellum. (B) A malformed fdl1-1 mutant embryo. Note the less curved scutellum, the uncovered shoot and the openings in coleoptile and first leaf surfaces. (C) The wild-type scutellum encloses the coleoptile, which contains the first leaf. (D) Higher magnification of the area framed in C shows the distinct coleoptile and leaf. (E) Laterally expanded scutellum, open coleoptile surface (arrows) and cleft leaf (arrowhead) are visible in the fdl1-1 mutant embryo shoot. (F) Higher magnification of the area framed in E. Note the lack of tissue identity between coleoptile and leaf in the fused region. co, coleoptile; lf, first leaf; sc, scutellum. Bars: 1mm (A); 100 μm (B, C, E); 25 μM (D, F).