DETERMINATION OF THE LIGHT PATHLENGTH ELONGATION IN LEAVES BY MEASURING P700 QUANTITATIVELY

P700 absorption change signals were measured at 800 nm for plant leave s and plant leaf extracts by illuminating with far-red light. The rati o of the signal amplitudes for the two sample types shows the degree o f optical signal intensification. The intensification is due to optica l path-length elongation, itself caused by scattering. The intensifica tion was found to be between 6 and 15 for different leaves. For spinac h leaves, the intensification varied less than 10% among samples. By r eplacing the air in the spongy layer of a leaf with an isotonic soluti on it was shown that nearly half of the intensification is due to the scattering at air-tissue interfaces. The comparison of the P700 signal s of a leaf with its extract would seem to be a new technique for dete rmining the optical scattering effects of leaves.