allvalues_Calluna.xlsx

The published images were analyzed and the obtained values were summarized in the Excel files.For measurement of the anatomical parameters, the software Optimas 6.5 (Media Cybernetics, L.P. Optimas, Rockville, MD) was used.Values were obtained as follows: within a 0.00316 mm² area of xylem the number of tracheae and tracheids (n_tt), the outer diameter (d_tt), and the cell wall thickness of those xylem elements (t_cw) were measured. From these values, the ratio of cell wall thickness to cell diameter (r = t_cw/d_tt) was calculated. Additionally, the whole xylem area in a cross section (A_x) was determined by using d_x and assuming a circular shape of the vascular tissue in a cross section. If pith tissue was present, the area of the pith tissue was subtracted from the xylem area. By knowing A_x and n_tt the total number of conducting xylem units in the cross sectional area of xylem (n) was calculated. There were only tracheids found in the transition zone (Z₃) and the basal part of the pedicel (Z₄), whose lengths (l_tr) were measured.