Fig. 4.

Electronic microscopic observation of mutant and wild-type pollen tubes. Pollen grains were cultured in vitro at 16 °C for 3 h and then used for ultrathin sections. All of the ultrathin sections were stained with osmium tetroxide. Images show an overview of the newly emerging pollen tubes of Col (A), csld1 (E, I), Ler (C), and csld4 (G, K), and high magnification of the cell wall of Col (B), csld1 (F, J), Ler (D), and csld4 (H, L) pollen tubes. Wild-type Col (A, B) and Ler (C, D) pollen tubes had a characteristic cell wall consisting of an outer fibrous pectin layer and an inner non-fibrous callose layer. Mutant pollen grains from csld1/+ (E–H) and csld4/+ (I–L) plants produced pollen tubes that exhibited thickened and highly irregular cell walls. Some of the csld1 (I, J) and csld4 (K, L) pollen grains produced pollen tubes without obvious non-fibrous materials in the tube wall. Arrows indicate blocks of fibrillar inclusions. ow, outer wall; iw, inner wall; w, wall; cyt, cytoplasm; pm, plasma membrane. Bars: (A, E, I, C, G and K) 2 μm; (B, F, J, D, H and L) 1 μm.