Photoacoustic spectra of green and red leaves of ficus Benjamina plant

Tissue samples of a ficus Benjamina plant are prepared in the shape of thick film for photoacoustic spectroscopy studies. Two absorption bands in the elec- tromagnetic photoacoustic (PA) spectrum are detected in the visible range. They are peaked at about 398 and 670 nm for a green leaf, and 544 and 570 nm for a red leaf. The absorption bands detected in the ultraviolet range are attributed to π  π* and π  n charge transfer transitions. The visible PA spectra strongly depend on the processes responsible for colouring of leaves. The absorption band at 670 nm could be related to photosynthesis. The absorption band observed at 398 nm for the green leaf disappears for the red one, though a different band located at 544 nm appears. The absorption spectra measured in this work are closely similar to those obtained earlier for the other living organisms. The absorption band near 544 nm is close to that found for spermidine, which is important in the information transfer to DNA. The results obtained in this work confirm experimentally that the red leaves absorb particularly strongly in that spectral region of solar radiation, which is intensely ra- diated in autumn.