Rapid and simultaneous approximations of photosynthetic photon flux density and net photosynthetic rate in a cherry tree [Prunus avium] canopy by thermal imaging

On calm days throughout the growing season, much data on photosynthetic photon flux density at leaf surface (PPFD) and net photosynthetic rate (Pn) of individual 'Napoleon' cherry leaves were collected along with several meteorological elements. From these data, two multiple regression formulas were derived: one, to estimate PPFD using leaf and air temperatures as the explanatory variables, two, to estimate Pn using the two temperatures, PPFD, number of days after full bloom of experimental date and time difference between noon and experimental hour. Our system combined these formulas with the data derived from the thermal images of layers in the foliar canopy. The images were obtained from a portable, non-cooling thermographic equipment. By this procedure, the approximations of both PPFD and Pn of pixel unit were possible. By a note-type personal computer, calculations of the two values and displays of these distribution images on the screen were made quickly.