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).
In order to simulate the potential short-term light use efficiency
(LUE per incident light) of photosynthesis under different light
sources, the normalized spectral power of three types of commercial
lamps (HPS: Philips Green Power 600W–400V; LED 645 nm:
Roithner LED type 645-66-60; LED 680 nm: Roithner LED type
680-66-60) were multiplied with the photosynthetic rate at each
wavelength, for the different lamp/leaf combinations (for spectral
output of the lamps see Paradiso et al. (in press)). The LUE at a given
light source wavelength was calculated from the LUE data by linear
interpolation.