CZECH POLAR REPORTS 8 (2): 249-259, 2018 ——— Received December 15, 2018, accepted January 17, 2019. * Corresponding author: M. Barták <mbartak@sci.muni.cz> Acknowledgements: The authors would like to express their thanks the CzechPolar2 (LM2015078) infrastructure, J. G. Mendel station at the James Ross Island (Antarctica). The study was also sup- ported by the ECOPOLARIS project (CZ.02.1.01/0.0/0.0/ 16_013/0001708). 249 Spectral reflectance indices sense desiccation induced changes in the thalli of Antarctic lichen Dermatocarpon polyphyllizum Miloš Barták 1* , Kumud Bandhu Mishra 1,2 , Michaela Marečková 1 1 Laboratory of Photosynthetic Processes, Section of Plant Physiology and Anatomy, Department of Experimental Biology, Faculty of Science, Masaryk University, Univer- sity Campus – Bohunice, Kamenice 5, 625 00 Brno, Czech Republic 2 Global Change Research Institute (CzechGlobe), The Czech Academy of Sciences, v. v. i, Bělidla 986/ 4a, 603 00 Brno, Czech Republic Abstract Lichens, in polar and alpine regions, pass through repetitive dehydration and rehydration events over the years. The harsh environmental conditions affect the plasticity of li- chen’s functional and structural features for their survival, in a species-specific way, and, thus, their optical and spectral characteristics. For an understanding on how dehydration affects lichens spectral reflectance, we measured visible (VIS) and near infrared (NIR) reflectance spectra of Dermatocarpon polyphyllizum, a foliose lichen species, from James Ross Island (Antarctica), during gradual dehydration from fully wet (relative water content (RWC) = 100%) to dry state (RWC = 0%), under laboratory conditions, and compared several derived reflectance indices (RIs) to RWC. We found a curvilinear relationship between RWC and range of RIs: water index (WI), photochemical reflec- tance index (PRI), normalized difference vegetation index (NDVI), modified chlorophyll absorption in reflectance indices (MCARI and MCARI1), simple ratio pigment index (SRPI), normalized pigment chlorophyll index (NPCI), and a new NIR shoulder region spectral ratio index (NSRI). The index NDVI was initially increased with maxima around 70% RWC and it steadily declined with further desiccation, whereas PRI in- creased with desiccation and steeply falls when RWC was below 10%. The curvilinear relationship, for RIs versus RWC, was best fitted by polynomial regressions of second or third degree, and it was found that RWC showed very high correlation with WI (R 2 = 0.94) that is followed by MCARI (R 2 = 0.87), NDVI (R 2 = 0.83), and MCARI (R 2 = 0.81). The index NSRI, proposed for accessing structural deterioration, was almost invariable during dehydration with the least value of the coefficient of determination (R 2 = 0.28). This may mean that lichen, Dermatocarpon polyphyllizum, activates pro- tection mechanisms initially in response to the progression of dehydration; however, severe dehydration causes deactivation of photosynthesis and associated pigments without much affecting its structure. DOI: 10.5817/CPR2018-2-21