Changes in spectral reflectance of a foliar lichen Umbilicaria hirsuta during desiccation

Abstract

Water potential (ψw) and water saturation deficit (WSD), and several reflectance (R) indexes were assessed in an aerophytic lichen Umbilicaria hirsuta (Sw. ex Westr.) Hoffm. The water index (WI, R 900/R970) and normalized difference vegetation index, NDVI [(R900-R680)/(R900+R680)] were strongly correlated both with the ψw and the WSD of lichen thalli. No significant changes during desiccation were found in structural independent pigment index, SIPI [(R800-R445)/(R 800-R680)]. Sensitivity of the spectral detection of water status was rather small at high hydration level (WSD < 25 %, or ψw > -1 MPa), but this is not much limiting its value and potential use, because physiological processes in lichens are usually inhibited at much lower values of ψw than in leaves of vascular plants. © 2007 Institute of Experimental Botany, ASCR.