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Your search keyword '"Poikilohydric organism"' showing total 2 results
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2 results on '"Poikilohydric organism"'

1. Laboratory and field measurements of water relations, photosynthetic parameters, and hydration traits in macrolichens in a tropical lower montane rainforest in Thailand.

Author

Boonpeng, Chaiwat, Pischom, Marisa, Butrid, Pawanrat, Noikrad, Sutatip, and Boonpragob, Kansri

Subjects
*TROPICAL forests, *TROPICAL dry forests, *LICHENS, *RAIN forests, *PHOTOSYNTHETIC rates, *HYDRATION
Abstract

Ecophysiological studies of lichens in tropical Asia are rare, and additional studies can increase the understanding of lichen life in this region. The main aim of this study was to observe the relationships between water availability and photosynthetic parameters, as well as hydration trait parameters, in macrolichens during the rainy and dry seasons in a tropical forest. A total of 11 lichen species growing in a lower montane rainforest in Thailand were collected and studied. The results clearly showed that the specific thallus mass (STM), net photosynthetic rate (Pn), the potential quantum yield of primary photochemistry (Fv/Fm), chlorophyll content, and carotenoid content of almost all lichens were lower in the dry season than in the rainy season. Field measurements in the dry season revealed that only the foliose chlorolichen Parmotrema tinctorum was metabolically active and exhibited slight carbon assimilation. In the rainy season, all lichens started their photosynthesis in the early morning, reached maximal values, declined, and ceased when the thalli desiccated. The photosynthetically active period of the lichens was approximately 2–3 h in the morning, and the activities of the cyanolichens ended approximately 30 min after the chlorolichens. The hydration trait parameters, including the STM, maximal water content (WCmax), and water holding capacity (WHC), were greater in the cyanolichens. In addition, the maximal Pn (Pnmax) and optimal water content (WCopt) for Pn were also greater in the cyanolichens, but the maximal Fv/Fm (Fv/Fmmax) was lower. The cyanolichens compensated for their inability to use humid air to restore photosynthesis by having higher water content and storage, higher photosynthetic rates, and longer photosynthetically active periods. This study provides additional insights into lichen ecophysiology in tropical forests that can be useful for lichen conservation. [ABSTRACT FROM AUTHOR]

Published
2024
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2. Ozone and desiccation tolerance in chlorolichens are intimately connected: a case study based on two species with different ecology

Author

Fabio Candotto Carniel, Giacomo Lorenzini, Mauro Tretiach, Elisa Pellegrini, Stefano Bertuzzi, Cristina Nali, Guido Incerti, Bertuzzi, Stefano, Pellegrini, Elisa, Candotto Carniel, Fabio, Incerti, Guido, Lorenzini, Giacomo, Nali, Cristina, and Tretiach, Mauro

Subjects
0106 biological sciences, 0301 basic medicine, Antioxidant, Parmotrema perlatum, Poikilohydric organisms, medicine.medical_treatment, Health, Toxicology and Mutagenesis, Ascorbic Acid, 01 natural sciences, Antioxidants, chemistry.chemical_compound, Ascorbate Peroxidases, Superoxides, Chlorophyll a fluorescence, Halliwell-Asada cycle, Oxidative stress, Environmental Chemistry, Pollution, Hydrogen peroxide, biology, Ecology, Superoxide, General Medicine, Glutathione, Poikilohydric organism, Health, Peroxidase, Lichens, Superoxide dismutase, 03 medical and health sciences, Xanthoria parietina, Ozone, Botany, medicine, Antioxidants Halliwell-Asada cycle Chlorophyll a fluorescence Oxidative stress Poikilohydric organisms, Toxicology and Mutagenesis, Desiccation, Superoxide Dismutase, Chlorophyll A, Water, Hydrogen Peroxide, biology.organism_classification, 030104 developmental biology, chemistry, biology.protein, Oxidative stre, 010606 plant biology & botany
Abstract

Tropospheric ozone (O3) causes severe damage to many vascular plants but not to lichens. It was recently suggested that this may be due to their high levels of natural defences against the oxidative bursts associated to their fluctuating water content. In this study, the combined effects of watering regime (with or without a daily spray of distilled water), air relative humidity (20 ± 5 vs. 80 ± 5% RH) and O3 (250 vs. 0 ppb, 5 h day−1 for 2 weeks) were monitored in two chlorolichens with different ecology, Parmotrema perlatum and Xanthoria parietina. Modulated chlorophyll a fluorescence (Chl a F), superoxide anion radical (O2 •−) and hydrogen peroxide (H2O2) production, antioxidant content and enzyme activity of the ascorbate/glutathione cycle were measured after exposure and, for Chl a F, after 1 and 2 days of recovery. The species differed in the antioxidant profile (ascorbate was higher in X. parietina, glutathione in P. perlatum), and in the activity of ROS-scavenging enzymes, more intense in the hygrophilous P. perlatum than in the meso-xerophilous X. parietina. O3 slightly modified Chl a F parameters related to the controlled dissipation, with reduction of Fm, Fv/Fm (both species) and ETR (in P. perlatum), and increase in NPQ and qN (in X. parietina). It also influenced, particularly in P. perlatum, the content of H2O2, glutathione (GSH) and oxidized glutathione (GSSG) (but not that of O2 •− and AsA + DHA) and the activity of superoxide dismutase, ascorbate peroxidase and dehydroascorbate reductase. These parameters, however, were more heavily affected by water availability. The hypothesis that lichens are O3-tolerant thanks to the constitutive antioxidant systems, intimately related to their poikilohydric life-style, is thus confirmed.

Published
2016

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