Near-Infrared Reflectance Spectroscopy allows rapid and simultaneous evaluation of chloroplast pigments and antioxidants, carbon isotope discrimination and nitrogen content in Populus spp. leaves

Poplar species are economically important sources of timber and bioenergy and they also have a valuableapplication in phytoremediation and in forest restoration programmes. The characterization of theirresponses in the face of environmental constraints is essential to ascertain their adaptation capacity.Quantification of chloroplast pigments and antioxidant compounds, nutrients and carbon isotope dis-crimination (D13C) of a large set of samples in ecophysiological studies is important for determiningthe plant's physiological responses.D13C and nitrogen are parameters of special interest for providinginformation on photosynthesis, water relations and nutritional characteristics in forest stands.Photoprotective and antioxidant compounds participate in the physiological defence of plants subjectedto stressful environmental conditions. The measurement of these leaf components by traditional tech-niques is laborious and expensive. To evaluate them, a calibration model was obtained using Near-Infrared Reflectance Spectroscopy (NIRS) and chemical analyses ofPopulusspp.leaves sampled from dif-ferent clones in different years under different physiological conditions. Predictive calibration equationsfor the concentration of chloroplast pigments (Chlorophyllsaandb, lutein, neoxanthin,b-carotene(b-Car), VAZ (violaxanthin + antheraxanthin + zeaxanthin), epoxidation index (EI = (0.5antheraxanthin+ violaxanthin)/VAZ)), antioxidants (total phenolics (TPhe), ascorbate anda-tocopherol),D13C and N con-tent were established using a partial least squares regression algorithm. Results showed a remarkableaccuracy of the calibration equations for quantifying several antioxidative and photoprotective defencecompounds such as neoxanthin (R2= 0.844),b-Car (R2= 0.827), VAZ (R2= 0.846), EI (R2= 0.831) andexcellent accuracy for TPhe (R2= 0.957), N (R2= 0.963) andD13C(R2= 0.922). As shown, results can beobtained on multiple physiological attributes with a single measurement, saving time and money anddemonstrating the suitability of NIRS for ecophysiological purposes and bioremediation programs.