spectral composition; irradiance; diffuse index; solar elevation angle

The radiation environment is traditionally quantified in terms of radiant energy and irradiance of PAR, but detailed characterization of spectral irradiance or photon flux distributions is missing. Information about changes of PAR spectral composition (and partly also out of this spectral region) during daytime, growing season and within the canopy layer is important both for understanding of differentiation of photosynthetic apparatus in natural environment and for determination of solar energy absorption and conversion efficiency on the level of individual leaves, plants and the whole canopy. Initially, we attempted to find relation between spectral characteristics (represented by the spectral ratios) and non - spectral parameters (represented by irradiance, diffuse index and solar elevation angle) as a tool for prediction of irradiance quality.

The radiation environment is traditionally quantified in terms of radiant energy and irradiance of PAR, but detailed characterization of spectral irradiance or photon flux distributions is missing. Information about changes of PAR spectral composition (and partly also out of this spectral region) during daytime, growing season and within the canopy layer is important both for understanding of differentiation of photosynthetic apparatus in natural environment and for determination of solar energy absorption and conversion efficiency on the level of individual leaves, plants and the whole canopy. Initially, we attempted to find relation between spectral characteristics (represented by the spectral ratios) and non - spectral parameters (represented by irradiance, diffuse index and solar elevation angle) as a tool for prediction of irradiance quality.