Interspecific differences in desiccation tolerance of selected Antarctic lichens: Analysis of photosystem II effectivity and quenching mechanisms

Lichens can survive and cope with unsufficient water supply resulting in low intrathalline relative water content. Under such conditions, photosynthesis is negatively affected by different degree of dehydration. In our study, fully hydrated samples of Xanthoria elegans, Umbilicaria decussata and Usnea aurantiaco-atra were light-acclimated and during following desiccation from a fully hydrated to dry state, steady-state chlorophyll fluorescence (FS), effective quantum yield of photochemical processes in PSII (ФPSII), and nonphotochemical quenching (qN) were measured in response to decreasing relative water content (RWC). The three experimental lichen species showed a high desiccation tolerance. The desiccation-induced decrease in ФPSII was found in X. elegans, U. decussata and U. aurantiaco-atra, at the RWC values below 30%. This is well comparable to the evidence reached in other Arctic / Antarctic lichen species. Interspecific differences in desiccation tolerance of these selected Antarctic lichens, based on the analysis of photosystem II effectivity and quenching mechanisms, were described and discussed

What does critical temperature tell us about the resistance of polar lichens to freezing stress? Applicability of linear cooling method to ecophysiological studies.

Lichens from polar regions are well adapted to low temperature and considered cryoresistant. However, interspecific differences in their cryoresistance exist according to the degree of their adaptation and severity of the environment. In our study, we applied linear cooling technique in order to evaluate the interspecific differences in several lichen species. Thalli segments of Umbilicaria antarctica, Nephroma antarctica, Placopsis contortuplicata and Lasallia pustulata were exposed to the cooling from 20 to –35°C at a constant rate of 2°C min-1. Simultaneously with the cooling, chlorophyll fluorescence parameters evaluating potential (FV/FM) and effective yield of primary photochemical processes in PSII (FPSII) were measured in 30 s interval. Temperature response curves of FV/FM and FPSII formed typical S-curves that were species specific. Critical temperature (cooling point at which FPSII equals 0), was found in a narrow range of –25 to –28°C, suggesting that all experimental lichen species have a high resistance to sub-zero temperatures. The method of linear cooling used in this study has proven its applicability in ecophysiological studies since it is sensitive enough for the evaluation of species-specific differences in cryoresistance. This study describes different parameters that can be derived from the S-curves and discuss their proper use in ecophysiological and stress physiology studies

Resistance of Primary Photosynthesis to Photoinhibition in Antarctic Lichen <i>Xanthoria elegans</i>: Photoprotective Mechanisms Activated during a Short Period of High Light Stress

The Antarctic lichen, Xanthoria elegans, in its hydrated state has several physiological mechanisms to cope with high light effects on the photosynthetic processes of its photobionts. We aim to investigate the changes in primary photochemical processes of photosystem II in response to a short-term photoinhibitory treatment. Several chlorophyll a fluorescence techniques: (1) slow Kautsky kinetics supplemented with quenching mechanism analysis; (2) light response curves of photosynthetic electron transport (ETR); and (3) response curves of non-photochemical quenching (NPQ) were used in order to evaluate the phenomenon of photoinhibition of photosynthesis and its consequent recovery. Our findings suggest that X. elegans copes well with short-term high light (HL) stress due to effective photoprotective mechanisms that are activated during the photoinhibitory treatment. The investigations of quenching mechanisms revealed that photoinhibitory quenching (qIt) was a major non-photochemical quenching in HL-treated X. elegans; qIt relaxed rapidly and returned to pre-photoinhibition levels after a 120 min recovery. We conclude that the Antarctic lichen species X. elegans exhibits a high degree of photoinhibition resistance and effective non-photochemical quenching mechanisms. This photoprotective mechanism may help it survive even repeated periods of high light during the early austral summer season, when lichens are moist and physiologically active

Translation of Cryobiological Techniques to Socially Economically Deprived Populations—Part 1: Cryogenic Preservation Strategies

Use of cold for preservation of biological materials, avoidance of food spoilage and to manage a variety of medical conditions has been known for centuries. The cryobiological science justified these applications in the 1960s increasing their use in expanding global activities. However, the engineering and technological aspects associated with cryobiology can be expensive and this raises questions about the abilities of resource-restricted low and middle income countries (LMICs) to benefit from the advances. This review was undertaken to understand where or how access to cryobiological advances currently exist and the constraints on their usage. The subject areas investigated were based on themes which commonly appear in the journal Cryobiology. This led in the final analysis for separating the review into two parts, with the first part dealing with cold applied for biopreservation of living cells and tissues in science, health care and agriculture, and the second part dealing with cold destruction of tissues in medicine. The limitations of the approaches used are recognized, but as a first attempt to address these topics surrounding access to cryobiology in LMICs, the review should pave the way for future more subject-specific assessments of the true global uptake of the benefits of cryobiology.Fil: Buriak, Iryna. National Academy of Sciences of Ukraine; UcraniaFil: Fleck, Roland. Kings College London; Reino UnidoFil: Goltsev, Anatoliy. National Academy of Sciences of Ukraine; UcraniaFil: Shevchenko, Nadiya. National Academy of Sciences of Ukraine; UcraniaFil: Petrushko, Maryna. National Academy of Sciences of Ukraine; UcraniaFil: Yurchuk, Taisiia. National Academy of Sciences of Ukraine; UcraniaFil: Puhovkin, Anton. National Academy of Sciences of Ukraine; UcraniaFil: Rozanova, Svitlana. National Academy of Sciences of Ukraine; UcraniaFil: Guibert, Edgardo Elvio. Universidad Nacional de Rosario. Secretaria de Ciencia y Técnica. Centro Binacional de Investigación en Criobiología Clínica y Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; ArgentinaFil: Robert, María Celeste. Universidad Nacional de Rosario. Secretaria de Ciencia y Técnica. Centro Binacional de Investigación en Criobiología Clínica y Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; ArgentinaFil: Juan de Paz, Leonardo. Universidad Nacional de Rosario. Secretaria de Ciencia y Técnica. Centro Binacional de Investigación en Criobiología Clínica y Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; ArgentinaFil: Powell Palm, Matthew J.. University of California at Berkeley; Estados UnidosFil: Fuller, Barry. University College London; Estados Unido