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Desiccation–rehydration experiments have been employed over the years to evaluate desiccation tolerance of bryophytes (Bryophyta, Marchantiophyta, and Anthocerotophyta). Researchers have applied a spectrum of protocols to induce desiccation and subsequent rehydration, and a wide variety of techniques have been used to study desiccation-dependent changes in bryophyte molecular, cellular, physiological, and structural traits, resulting in a multifaceted assortment of information that is challenging to synthesize. We analysed 337 desiccation–rehydration studies, providing information for 351 species, to identify the most frequent methods used, analyse the advances in desiccation studies over the years, and characterize the taxonomic representation of the species assessed. We observed certain similarities across methodologies, but the degree of convergence among the experimental protocols was surprisingly low. Out of 52 bryophyte orders, 40% have not been studied, and data are lacking for multiple remote or difficult to access locations. We conclude that for quantitative interspecific comparisons of desiccation tolerance, rigorous standardization of experimental protocols and measurement techniques, and simultaneous use of an array of experimental techniques are required for a mechanistic insight into the different traits modified in response to desiccation. New studies should also aim to fill gaps in taxonomic, ecological, and spatial coverage of bryophytes. [ABSTRACT FROM AUTHOR]

Main conclusion: The expansion of crustose lichens in the Negev is principally determined by dew and that of fruticose lichens by fog. Crustose and fruticose lichens are largely adapted to dew and fog, respectively. Although crustose and fruticosea lichens were shown to efficiently use dew and fog, the link between their expansion and the occurrence of dew and fog has never been shown experimentally. This is also the case for the Negev Desert Highlands, where (i) dewless habitats were not inhabited by lichens and (ii) an increase in fruticose lichens with high-altitude fog-prone areas was noted, leading us to hypothesize that the expansion of crustose and fruticose lichens is mainly linked to dew and fog, respectively. Experiments aiming to compare the non-rainfall water (NRW) were conducted. We used cloths attached to 7 cm-high cobbles to mimic crustose lichens (MCL), cloths placed horizontally aboveground to evaluate the amount of NRW without the presence of the cobble (CoP), cloths attached to a wire scaffold mimicking fruticose lichens (MFL), and cloths attached to glass plates (CPM) that served as a reference. Substrate temperatures were compared to the dew point temperature. In addition, sprinkling experiments, which mimicked fog under variable wind speeds (0.9, 1.4, 3.3 and 5.7 m s−1), were also conducted. NRW followed the pattern: MCL ≈ CPM > CoP > > MFL. While MCL yielded substantially higher amounts of NRW (0.09 mm) in comparison to MFL (0.04 mm) during dew events, similar amounts were obtained by both substrates (0.15–0.16 mm) following fog. However, fog interception increased substantially with wind speed. The findings may explain the expansion of crustose lichens in extreme deserts benefiting mainly from dew (but also fog), and the proliferation of fruticose lichens in fog-prone areas, especially when accompanied by high-speed winds. While (mainly) high proliferation of crustose lichens may serve as bioindicators for dew in extreme deserts, fruticose lichens may serve as bioindicators for fog. [ABSTRACT FROM AUTHOR]

Simultaneous in vivo measurements of prompt fluorescence (PF), delayed fluorescence (DF) and modulated reflection (MR) at 820-nm were used to assess effect of short desiccation period (4.5 h) on Parmelina tiliacea lichen. The two performance indexes (PI ABS and PI total ) as a measure of an overall photosynthetic thalli performance showed a negative effect of desiccation treatment on photosynthetic activity. The maximal intensity of PF and DF recorded during desiccation treatment decreased and at 4.5 h desiccation time Parmelina tiliacea thalli loss their variable fluorescence and DF amplitude. This loss of variable fluorescence was due to an increase in inactive reaction centers and a limitation of electron donation on the donor side of photosystem II (PSII) that caused a down-regulation of electron transport chain at the PSII level. However, the efficiency with which an electron can move from the reduced intersystem electron acceptors to the PSI end electron acceptors was less affect by desiccation treatment. In respect to MR change, re-reduction kinetics of the primary electron donors of photosystems I (P700) and plastocyanin (PC) in desiccated thalli seem to be faster, their amplitudes gradually decrease and a disconnection between the two photosystem (PSII and PSI) were observed. These responses allow to Parmelina tiliacea lichen a photoprotection mechanism from the excess light excitation. [ABSTRACT FROM AUTHOR]

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 (ChlaF), 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 ChlaF, 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 ChlaF 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. [ABSTRACT FROM AUTHOR]

The purposes of this article are to quantify the relationship between epiphytic lichen distribution and macroclimatic variables in the study area and to provide a case study for evaluating the predictive role of epiphytic lichens as bioclimatic indicators. The study was carried out in the Liguria region (NW-Italy), a small (5432 km2) borderline area, where phytoclimatic features range from the dry Mediterranean to the Alpine in a few kilometers. Epiphytic lichen diversity was sampled using a standardized protocol [Asta et al () In: Nimis et al (eds) Monitoring with lichens: monitoring lichens. Kluwer, Dordrecht]. Abundance of the species in the sampling sites was related to macroclimatic parameters (yearly average temperature and rainfall) and non-parametric multivariate models were calculated to find significative relationships among predictive and response variables. A total of 59 species showed highly significant relation with macroclimatic parameters. Four groups were selected, by means of a cluster analysis, related to four climatic niches (warm-humid, cold-humid, mesothermic-humid, warm-dry). Distributional pattern of the groups in the survey area showed a good correspondence with the bioclimatic units of Liguria region described by Nimis [() Checklist of the Lichens of Italy 3.0. University of Trieste, Dept of Biology. http://www.dbiodbs.univ.trieste.it. Cited 1 Jun 2006]. A significant subset of epiphytic lichen species in the study area have been proved to be efficient bioclimatic indicator and it is supposed to give good results to monitor climatic changes, in a long-term perspective. [ABSTRACT FROM AUTHOR]

This study aims to assess the photoprotective potential of desiccation-induced curling in the light-susceptible old forest lichen Lobaria pulmonaria by using chlorophyll fluorescence imaging. Naturally curled thalli showed less photoinhibition-induced limitations in primary processes of photosynthesis than artificially flattened specimens during exposures to 450 μmol m−2 s−1 in the laboratory after both 12- (medium dose treatment) and 62-h duration (high dose treatment). Thallus areas shaded by curled lobes during light exposure showed unchanged values of measured chlorophyll fluorescence parameters ( F V/ F M, ΦPS II), whereas non-shaded parts of curled thalli, as well as the mean for the entire flattened thalli, showed photoinhibitory limitation after light treatments. Furthermore, the chlorophyll fluorescence imaging showed that the typical small-scale reticulated ridges on the upper side of L. pulmonaria caused a spatial, small-scale reduction in damage due to minor shading. Severe dry-state photoinhibition readily occurred in flattened and light-treated L. pulmonaria, although the mechanisms for such damage in a desiccated and inactive stage are not well known. Natural curling is one strategy to reduce the chance for serious photoinhibition in desiccated L. pulmonaria thalli during high light exposures. [ABSTRACT FROM AUTHOR]