Relationships between maximum stomatal conductance, gswmax, and leaf nitrogen per unit area, Na, determined in ‘Fuji’ and ‘Braeburn’ apple cultivars. In the linear equation (gswmax = aN Na + bN) the fitting parameters are: ‘Fuji’: aN = 0·074, bN = –0·020 (R2 = 0·74); ‘Braeburn’: aN = 0·062, bN = –0·038 (R2 = 0·77). The ANCOVA with Na as the covariate detected significant differences (P = 0·005) between the cultivars. Mean gswmax values followed by different letters are significantly different: ‘Fuji’, 0·19a, ‘Braeburn’, 0·12b.