FTIR-ATR spectroscopy – a new approach in root discrimination of crop and weed species

Crop and weed species often compete for the same resources. To analyse below-ground competitive processes, crop and weed roots have to be distinguished from one another. Up to now, a reliable and easy method for plant root discrimination does not exist. In a recent study, Fourier transform infrared (FTIR) spectroscopy with an attenuated total reflection (ATR) device was successfully applied in root discrimination of distantly related plant species (pea/oat). In this experiment, we wanted to test the potential of FTIR-ATR spectroscopy to discriminate roots of closely related crop/weed-combinations. In a greenhouse experiment, two crop and associated weed species were cultivated: Maize/barnyard grass (Zea mays/Echinochloa crus-galli) and sugar beet/common lambsquarters (Beta vulgaris/Chenopodium album). To allow inter- and intra-specific competition, plants were grown sole and in crop/weed-combinations. Six weeks after sowing, root biomass was harvested and rinsed with water to remove soil particles. The absorbance patterns of fresh and dry rootlets were recorded by FTIRATR spectroscopy. Spectra of fresh rootlets within one plant family showed similar peak distribution, while dry rootles differ in peak location and height. Cluster analyses grouped the absorbance patterns of the dry crop and weed roots according to their similarity and revealed a complete root discrimination of crop and weed species