After the photosynthesis measurements, the top leaflet was removed from the plant and leaf transmittance (Tr) and reflectance (Ref) spectra were measured between 400 and 740nm (bandwidth 1 nm), with a spectrophotometer (Perkin Elmer Lambda 950 UV/NIR; Perkin Elmer Inc. Waltham, MA, USA). For transmission measurements, the leaf was clamped to the input port of the integrating sphere with the bottom (abaxial side) facing the integrating sphere. For reflection measurements, the leaf was clamped to the exit port with the top (adaxial side) facing the sphere. In all measurements,
the leaves were illuminated from the top side and the direction of the collimated light was perpendicular to the leaf plane.
Leaf absorptance (Abs) at the used wavelengths was calculated as Abs = 100 – (Ref + Tr). All values were expressed as percentage of
the incoming light.