where a and b are regression coefficients for the relation between anthocyanin content and reflectance. Reflectance measurements were performed with a spectrophotometer as described above. The regression coefficients for rose leaves cultivar ‘Akito’ were determined on 18 leaves of different ages (and colour) and they were 54.52 for coefficient a and 45.93 for coefficient b. In these 18 leaves reflectance was measured and the anthocyanin content was analytically determined according to Martin et al. (2002). Regression analysis on these data showed that Eq. (1) gave a reliable estimate of anthocyanin content (R2 = 0.74).