The photochemical reflectance index (PRI), based on reflectance signatures at 531 and 570 nm, and associated with xanthophyll pigment inter-conversion and related thylakoid energisation, was evaluated as an indicator of photosynthetic function in a Mediterranean holm oak (Quercus ilex L.) coppice. The chlorophyll fluorescence pulse-amplitude-modulation and the eddy correlation techniques were used to estimate the photosystem 2 photochemical efficiency of leaves and the CO2 flux over the canopy, respectively. The reflectance and fluorescence techniques yielded identical estimates of the photosynthetic activity in leaves exposed to dark-light-dark cycles or to a variable irradiance in laboratory. However, there was no such correlation between photosynthetic performance and PRI when applied to a sun-exposed canopy in field conditions. Fluorescence profiles inside the canopy and especially a helpful use of multispectral reflectance imaging highlight the limitations of such method.
Shoots of damaged Quercus dalechampii Ten. saplings were shorter and their growth lagged behind by more than one week compared to the control shoots. Photosynthetic activity in leaves of the damaged trees was significantly lowered. Yet the leaf dark respiration rate was higher in damaged saplings. Changes of both the growth and leaf photosynthetic activities may also be ušed as a sensitive diagnostic parameter in ascertaining the negative effects of abiotic and/or biotic factors of the environment.