Seasonal variation in the reflectance of photosynthetically active radiation from epicuticular waxes of Scots pine (Pinus sylvestris) needles

Epicuticular waxes influence leaf reflectance, but the spatiotemporal dynamics in their reflectance properties have not been properly characterized, and its consequences remain unknown. In this study, we analysed the seasonal changes in wax reflectance of Scots pine needles. It tended to decrease with needle age and towards lower positions within the canopy. In addition, we also identified a clear seasonal pattern of variation superimposed on the of above-mentioned wax weathering effect. We conclude that spatiotemporal dynamics in wax optical properties need to be considered in studies that implicitly assume constant light absorption, particularly when different leaf age classes, canopy positions or seasons are compared, and especially in species with substantial amount of waxes. We suggest that the observed dynamics in wax reflectance could represent a new photoprotective mechanism operating at the seasonal scale as they modulate the absorption of the photosynthetically active radiation (PAR) over time.