DOI: 10.1007/s11099-013-0063-9 PHOTOSYNTHETICA 51 (4): 630-640, 2013 630 Effect of high temperature on dehydration-induced alterations in photosynthetic characteristics of the resurrection plant Haberlea rhodopensis M. VELITCHKOVA * , V. DOLTCHINKOVA ** , D. LAZAROVA *** , G. MIHAILOVA **** , S. DONCHEVA **** , and K. GEORGIEVA ****,+ Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev str. Bl. 21, 1113 Sofia, Bulgaria * Faculty of Biology, Sofia University “St. K. Ohridski”, 8 Dragan Tsankov Blvd., 1164 Sofia, Bulgaria ** Faculty of Medicine, Sofia University “St. K. Ohridski”, 1 Kozyak str., 1407 Sofia, Bulgaria *** Institute of Plant Physiology and Genetics, Bulgarian Academy of Sciences, Acad. G. Bonchev str. Bl. 21, 1113 Sofia, Bulgaria **** Abstract The effect of high temperature (HT) and dehydration on the activity of photosynthetic apparatus and its ability to restore membrane properties, oxygen evolution, and energy distribution upon rehydration were investigated in a resurrection plant, Haberlea rhodopensis. Plants growing under low irradiance in their natural habitat were desiccated to air-dry state at a similar light intensity [about 30 μmol(photon) m –2 s –1 ] under optimal day/night (23/20C) or high (38/30C) temperature. Our results showed that HT alone reduced the photosynthetic activity and desiccation of plants at 38C and it had more detrimental effect compared with desiccation at 23°C. The study on isolated thylakoids demonstrated increased distribution of excitation energy to PSI as a result of the HT treatment, which was enhanced upon the desiccation. It could be related to partial destacking of thylakoid membranes, which was confirmed by electron microscopy data. In addition, the surface charge density of thylakoid membranes isolated from plants desiccated at 38°C was higher in comparison with those at 23°C, which was in agreement with the decreased membrane stacking. Dehydration led to a decrease of amplitudes of oxygen yields and to a loss of the oscillation pattern. Following rehydration, the recovery of CO 2 assimilation and fluorescence properties were better when desiccation was performed at optimal temperature compared to high temperature. Rehydration resulted in partial recovery of the amplitudes of flash oxygen yields as well as of population of S 0 state in plants desiccated at 23°C. However, it was not observed in plants dehydrated at 38°C. Additional key words: desiccation; photosynthesis; thylakoid membranes. Introduction Desiccation-tolerant or resurrection plants have the unique ability to survive desiccation to air-dry state and they quickly restore their normal physiological activity upon rehydration. In this context, resurrection plants are interesting model systems to analyze resistance to the severe desiccation (Bartels et al. 1996). In order to survive in dry environments, plants must limit damage from desiccation and/or rehydration to a minimum, maintain cellular integrity in the dehydrated state, and activate repair mechanisms upon rehydration (Bewley 1995). The protection against a desiccation damage in angiosperms includes the production of nonreducing di- and oligosaccharides, various compatible solutes, and specific proteins, such as the late embryogenesis abun- dant proteins and heat shock proteins, some changes in lipid composition, and production of antioxidants ——— Received 30 October 2012, accepted 16 April 2013. + Corresponding author; phone: +359 2 979 2620, fax: +359 2 873 9952, e-mail: katya@bio21.bas.bg Abbreviations: BSA – bovine serum albumin; Chl a – chlorophyll a; Chl b – chlorophyll b; E – transpiration; EPM – electrophoretic mobility; HEPES – 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; HT – high temperature; g s – stomatal conductance; LHCI – light-harvesting complex of photosystem I; LHCII – light-harvesting complex of photosystem II; MES – 2-[N-morpholino] ethanesulfonic acid; OE – oxygen-evolving; P N – net photosynthetic rate; PS – photosystem; RWC – relative water content; ı – surface charge density; ζ – zeta potential. Acknowledgement: This work is supported by National Science Fund of Bulgaria under Research project ДO02–208/2008.