Possibility of Light-Induced Mid-IR Emission in Situ Analysis of Plants

We perform the spectral analysis of fresh leaves using light-induced mid-IR emission spectroscopy (LIMIRES), a technique utilizing CW optical pumping for preparing and monitoring vibrationally excited states of chromophores. We show how to obtain high-quality IR-emission spectra of intact leaves using visible light of low intensity and sensitive Fourier transform infrared spectroscopy (FTIR). Changing the conditions of illumination, we carry out the spectral discrimination between leaf samples of wild plants and transgenic tobacco plants. Our results show that LIMIRES is a valuable new technique for studying the vibrational structure of excited pigments as well as the nondestructive monitoring of the quality of tobacco leaves.