Fig. 2. Phyllotaxis defects of mir164abc triple-mutant plants. (A,B,F-I) SEM pictures and (C-E) photographs of Col-0 wild-type plants (A,E,F,H) and mir164abc mutants (B,C,D,G,I). (A,B) Initiating flower primordia follow a spiral phyllotactic pattern in the wild type (A) and in mir164abc triple mutants (B). Numbers indicate the succession of floral bud initiation. (B) Arrowheads in B point to sepal primordia of different sizes. (C-E) Flowers of mir164abc triple-mutant plants are arranged randomly along the stem (C,D) when compared with the regular pattern of Col-0 wild-type flowers (E). i, internode. (F-I) Stem internodes are uniformly covered with long and rectangular epidermal cells in the wild type (F,H), whereas clustered flowers in mir164abc triple-mutant plants are separated by few, variably shaped non-elongate cells (G,I). In H,I, the margins of equivalent cells are highlighted to demonstrate the differences in cell shape and size. (J) Distribution of size classes, each comprising a specific internode length. The number of internodes ('Number/category') falling into a specific size category are plotted against the size categories ('Size category [mm]'). The internode sizes of the mixed Ler/Col-0 wild-type control (wt, gray) are distributed around the mean value 8.7±3.6 (s.d., n_tot=149), whereas internode distribution of the mir164abc mutant (m, black) does not follow a similar pattern. (K) The average internode distance (in mm) is 8.7±3.6 (s.d., n_tot=149) for the wild-type control (wt, gray) and 8.6±8.6 (s.d., n_tot=150) for mir164abc triple-mutant (m, black) plants. Error bars indicate s.d. Scale bars: 20 µm in A,B; 100 µm in F-I.