Application of ATR-Fourier transform infrared spectroscopy in fast and simultaneous determination of leaf chemical and functional properties of forest herb species

ATR-Fourier transform infrared spectroscopy was used to determine the carbon and nitrogen content in the leaves of herbaceous forest plant species and functional traits associated with the leaf economic spectrum (one of the two-dimensional global spectrum of plant form and function), and monitoring plant physiological status under elevated temperature conditions. The content of carbon and nitrogen determined by traditional methods validated the accuracy of ATR-FTIR method. It was also shown that in the case of forest herbs, the ATR-FTIR method is an efficient tool for determining functional traits (such as specific leaf area (SLA) and leaf dry matter content (LDMC)) related to the leaf economics spectrum, and to diagnose the photophysiological state of plants after changes of temperature (changes of day/night temperature from 21/13 °C to 25/17 °C). Measuring the areas of three absorption bands of the ATR-FTIR spectra related to amides I and II (between 1700 cm⁻¹ and 1500 cm⁻¹), carbohydrates (cellulose and hemicellulose; between 1200 cm⁻¹ - 850 cm⁻¹) and amide III (between 1290 cm⁻¹ and 1190 cm-¹) allowed for determination of all analysed chemical and functional properties of leaves. Based on selected absorption bands accurately estimated C and N content, with coefficients of correlation (r) of 0.88 for C and 0.84 for N. SLA and LDMC were also predicted, with r values of 0.88 and −0.91, respectively. Moreover, ATR-FTIR proved to be a rapid, non-destructive tool for monitoring the plant physiological status, as demonstrated by the significant correlation (r = 0.99) between the chlorophyll fluorescence performance index (PI) and ATR-FTIR data. ATR-FTIR has been demonstrated as an efficient tool for simultaneous quantification of leaf carbon and nitrogen content, economic functional traits, and physiological status of forest herb plants.