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.