Fig. 6. Exogenous spermine modifies tracheary element differentiation in Zinnia elegans xylogenic cell cultures. (A) Tracheary element (TE) differentiation efficiency, expressed as the number of TEs as a percentage of all cells, in response to 50-200 µM spermine 84 and 168 hours after the initiation of the cell culture. (B) Proportion of the different types of TEs at 168 hours in response to 50-200 µM spermine. (C) The size of the TEs (±s.e.m.) after 168 hours in response to 50-200 µM spermine. Statistics are presented (C) for each treatment compared with the previous treatment, using a Kruskal-Wallis test (^***P<0.005). (D) Typical TEs after 168 hours without the addition of spermine. (E) Typical TEs 168 hours after the addition of 200 µM spermine. Scale bar: 50 µm in D,E.