CSLD2 and CSLD6 are redundant and required for normal phyllid development. (A and H) Phyllid development proceeds normally in wild-type (A and B), csld2KO (C and D), and csld6KO (E and F) plants. In contrast, the phyllids of double csld2/6KO plants (G and H) show a variety of morphological defects including midribs that do not extend to the tips (white asterisk), formation of protonema-like filaments on the leaf margins (black asterisk) and bulges that sometimes extend to form tube-like structures (black arrowhead). Minor defects consisting of cell separations surrounded by cells with altered growth orientation (white arrowheads) are found in csld6KO (F) and csld2/6KO (H) phyllids. (I–N) Phyllids stained with Pontamine Fast Scarlet 4B (S4B) and imaged with confocal scanning laser microscopy. Cells elongate parallel to the phyllid axis in wild type (I). Cell adhesion and expansion defects in csld2/6KO plants (J–N) include structures that form where cells surrounding a small cell separation elongate in a radial pattern (J, arrowhead), bulges that form as cells surrounding a small separation elongate and divide (K, arrowhead), large cell separations (L, arrowhead), midribs that end abruptly instead of extending to the leaf tip (M, arrowhead), and marginal cells that extend as filaments that superficially resemble protonemata (N, arrowhead). Scale bars, 2 mm (A, C, E, and G), 200 μm (B, D, F, and H), and 50 μm (I and J–N).