Fig. 4

Developmental progression of stomatal differentiation and mesophyll airspace formation. a–f Confocal images of leaf 3 of wheat (6n) seedlings taken either at the distal tip region (a–c) or proximal base (d–f). Images are from the epidermis (a, d) or subtending mesophyll (b, e), with cell walls false-coloured and overlaid in (c, f). A mature stomata is visible in a, with two immature stomata in d. A large airspace subtends the stomata in a (indicated by asterisks in b, c). Small airspaces (asterisks) are visible in e, f at cell junctions. g–l Confocal images of Arabidopsis leaves at maturity (g–i) or early development (j–l). Images are from the epidermis (g, j) or subtending mesophyll (h, k) with cell wall false-coloured and overlaid in i, l. A mature stomata is visible in centre (g), with numerous stomata at various developmental stages in j. A relatively large airspace (asterisks) is visible below the central stomate (h), whereas some very small airspaces (asterisks) are distributed within the immature mesophyll (k, l) at cell junctions. Scale bar c, f = 20 µm; i, l = 25 µm