Chlorophyll a fluorescence and CO2 exchange of Umbilicaria aprina under extreme light stress in the cold

A lichen growing in a continental Antarctic region with low temperatures and strong irradiance in summer was investigated for evidence of photoinhibition. Field experiments with Umbilicaria aprina from a sheltered site with heavy snowpack showed no effects of photoinhibition when the lichen was exposed to strong sun irradiance for nearly 11 h a day. This was evident from CO₂ exchange and simultaneous chlorophyll a fluorescence measurements. CO₂ exchange was also not affected if quartz glass allowing greater UV penetration, was used as a lid for the cuvette. The dependency of net photosynthesis on photosynthetic photon flux density suggests that the lichen is photophilous. Received: 2 April 1997 / Accepted: 11 August 1997     

The influence of water on CO2 exchange in the lichen Parmelia praesignis Nyl.

Net photosynthetic rates for the lichen Parmelia praesignis Nyl. were obtained as a function of 5 light levels, 5 temperature levels, and of water content as thalli dried from saturated conditions. Data are described as second order polynomials in the light, and as saturation curves in the dark. Rates in the light were depressed at high water contents reaching maximal rates between 110% and 180% water content and declining as thalli dried. Physiological parameters were derived from the drying curves to investigate temperature and light interactions. Dark respiration parameters are the maximal rate, the water content where the rate is half-maximal, the water content at which respiration is zero, and the maximal water efficiency. In the light, parameters are the maximal net photosynthetic rate, the water content at the maximal rate, the water compensation point, the maximal water efficiency, and the sensitivity of net photosynthesis to change in water content.Values of half-maximal rate water contents for respiration were found to increase as temperatures increased. The greatest maximal net photosynthetic rate occurred at higher temperatures as the light intensity increased. In the light, maximal water efficiency and the sensitivity to changes in water content were generally maximal at temperatures yielding the greatest maximal net photosynthetic rates.     

Spatial organization of the three‐component lichen Peltigera aphthosa in functional terms

The cephalolichen Peltigera aphthosa (L.) Willd. is characterized by lateral heterogeneity, which manifests itself in the presence of three thallus zones, referred to as the apical, basal and medial zone. These zones differ in terms of interaction between lichen bionts and their physiological activity. The apical thallus zone is more efficient in establishing a contact with cyanobacteria, because of a higher lectin content and a larger overall thallus surface area due to the presence of numerous mycobiont hyphae. Cephalodia are formed in this zone. The interaction between the mycobiont and cyanobiont is more intense in the medial zone. However, the establishment of the contact with cyanobacteria in this zone less probable. The spatial distribution of lectins in the thallus was determined. To reveal the differences in photosynthetic activity in three thallus zones, transient analysis of chlorophyll a fluorescence and the assessment of non‐photochemical quenching of excited chlorophyll states were performed. Assimilation of absorbed light energy was more effective in the medial zone. The basal zone was characterized by decreased photosynthetic activity, lichen dissociation and thallus death.     

Will climate warming exceed lethal photosynthetic temperature thresholds of lichens in a southern African arid region?

Predicted elevated temperatures and a shift from a winter to summer rainfall pattern associated with global warming could result in the exposure of hydrated lichens during summer to more numerous temperature extremes that exceed their thermal thresholds. This hypothesis was tested by measuring lethal temperature thresholds under laboratory and natural conditions for four epilithic lichen species (Xanthoparmelia austro‐africana, X. hyporhytida, Xanthoparmelia sp., Xanthomaculina hottentotta) occurring on quartz gravel substrates at a hot arid inland site two epigeous lichen species (Teloschistes capensis, Ramalina sp.) occurring on gypsum‐rich topsoil at a warm humid coastal site. Extrapolated lethal temperatures for photosynthetic quantum yield under laboratory conditions were up to 4°C higher for lichens from a dry inland site than those from a humid coastal site. Lethal temperatures extrapolated for photosynthetic quantum yield at a saturating photosynthetic photon flux density of ≥11,000 μmol photons m^?2 s^?1 under natural conditions were up to 6°C higher for lichens from the dry inland site than the more humid coastal site. It is concluded that only under atypical conditions of lichen exposure in a hydrated state to temperature extremes at high midday solar irradiances during summer could lethal photosynthetic thresholds in sensitive lichen species be potentially exceeded, but whether the increased frequency of such conditions with climate warming would lead to increased likelihood of lichen mortality is debatable.     

Light use efficiency of dry matter gain in five macro-lichens: relative impact of microclimate conditions and species-specific traits

Relations between irradiance (I) and lichen growth were investigated for five macro‐lichens growing at two sites in Sweden. The lichens represented different mycobiont–photobiont associations, two morphologies (foliose, fruticose) and two life forms (epiphytic, terricolous). The lichens were transplanted at two geographically distant sites in Sweden (1000 km apart) from Sept 1995 to Sept 1996 in their typical microhabitats, where microclimate and growth were followed. Between April/May and Sept 96, the terricolous species had a dry matter gain of 0·2 to 0·4 g (g DW)^–1 and the epiphytes 0·01 to 0·02 g (g DW)^–1. When related to area, growth amounted to 30 to 70 g m^?2 for the terricolous species and to 1 to 4 g m^?2 for the epiphytes. There was a strong correlation between growth and intercepted irradiance when the lichens were wet (I_wet), with 0·2 to 1·1 g lichen dry matter being produced per MJ solar energy. Across the 10 sets of transplants, light use efficiencies of dry matter yield (e) ranged between 0·5 and 2%, using an energy equivalent of 17·5 kJ g^?1 of lichen dry matter. The higher productivity of the terricolous species was due to longer periods with thallus water contents sufficient for metabolic activity and because of the higher mean photon flux densities of their microhabitat. A four‐fold difference in photosynthetic capacity among the species was also important. It is concluded that lichen dry matter gain was primarily related to net carbon gain during metabolically active periods, which was determined by light duration, photon flux density and photosynthetic capacity.     

Ecological and physiological investigations in continental Antarctic cryptogams

Summary Microclimate and CO₂ exchange of the lichen Usnea sphacelata were measured during summen on a hill near Casey Station, Bailey Peninsula, Wilkes Land, Antarctica. Within a period of 52 days (November 10 until December 31, 1985), 8 diurnal courses of net photosynthesis were measured in naturally snow-covered lichen thalli, and 9 diurnal courses in thalli experimentally sprayed with melt water. Photosynthetic performance of a light-form of Usnea sphacelata was compared with that of a shade-form. Net photosynthesis was reversibly depressed in snow-covered lichen thalli of both forms when irradiance was higher than 600 mol m^–2 s^–1 photosynthetic active radiation (PAR), the depression persisting several hours after a period of strong light. These responses suggest photoinhibition. Models of photosynthesis were established for the light-form by non-linear regressions with field data from water-sprayed thalli (Model W) and field data measured in snow-covered lichens (SNO I, SNO II). Model SNO I is based on median values of photosynthetic rates and SNO II on maximum values for each light/temperature combination. Photosynthetic rates were calculated using model W; the results showed values approximately three times higher than measured in the field with naturally moistened thalli. Photosynthetic rates according to model SNO II fitted the data of naturally moistened lichens measured during the day, before strong light (> 600 mol m^–2s^–1 PAR) caused reversible decrease of net photosynthesis. Model SNO I fitted the data measured during and after a phase of strong irradiance. Model SNO I demonstrated that light stress was highest at temperatures below 2 °C. This study has shown that long-term calculation of the photosynthetic productivity must take into account decreases in net photosynthesis rate caused by strong light, as well as effects of water content and temperature. For the investigated period of the austral summer, a carbon production of 3.44 gm^–2 was estimated for U. sphacelata.     

Metabolic processes sustaining the reviviscence of lichen <Emphasis Type="Italic">Xanthoria elegans</Emphasis> (Link) in high mountain environments

To survive in high mountain environments lichens must adapt themselves to alternating periods of desiccation and hydration. Respiration and photosynthesis of the foliaceous lichen, Xanthoria elegans, in the dehydrated state were below the threshold of CO₂-detection by infrared gas analysis. Following hydration, respiration totally recovered within seconds and photosynthesis within minutes. In order to identify metabolic processes that may contribute to the quick and efficient reactivation of lichen physiological processes, we analysed the metabolite profile of lichen thalli step by step during hydration/dehydration cycles, using ³¹P- and ¹³C-NMR. It appeared that the recovery of respiration was prepared during dehydration by the accumulation of a reserve of gluconate 6-P (glcn-6-P) and by the preservation of nucleotide pools, whereas glycolytic and photosynthetic intermediates like glucose 6-P and ribulose 1,5-diphosphate were absent. The large pools of polyols present in both X. elegans photo- and mycobiont are likely to contribute to the protection of cell constituents like nucleotides, proteins, and membrane lipids, and to preserve the integrity of intracellular structures during desiccation. Our data indicate that glcn-6-P accumulated due to activation of the oxidative pentose phosphate pathway, in response to a need for reducing power (NADPH) during the dehydration-triggered down-regulation of cell metabolism. On the contrary, glcn-6-P was metabolised immediately after hydration, supplying respiration with substrates during the replenishment of pools of glycolytic and photosynthetic intermediates. Finally, the high net photosynthetic activity of wet X. elegans thalli at low temperature may help this alpine lichen to take advantage of brief hydration opportunities such as ice melting, thus favouring its growth in harsh high mountain climates.     

Net photosynthetic recovery in subarctic lichens with contrasting water relations

Summary The rates of net photosynthetic recovery after wetting for six subarctic lichens were related to their drying rates under laboratory conditions. Net photosynthetic recovery was described by the three parameters of the Von-Bertalanffy equation: T _o and K, related to the rates of resaturation respiration and gross photosynthetic recovery, and P _max, the photosynthetic maximum attained at full recovery. The time to full photosynthetic recovery ranged from 143 to 510 min and was positively correlated with the drying rate of the thallus. In order from most to least rapid recovery, the species are Coelocaulon divergens, Cetraria cucullata, Alectoria ochroleuca, Cladina stellaris, Nephroma arcticum, and Cladonia sulphurina.In nature the high evaporative resistance or low waterholding capacity characterizing fast-drying species will result in short, frequent cycles of wetting and drying which induce carbon losses. In such situations a rapid photosynthetic recovery should be adaptive since it increases photosynthetic carbon gain during a period of metabolic activity. We hypothesize that fast-drying species achieve their rapid photosynthetic recovery by an increased desiccation-tolerance which has a metabolic cost associated with it. In slowdrying species a rapid recovery is not favored by natural selection since these species can take advantage of longer photosynthetic activity periods and are exposed less frequently to deleterious wetting and drying cycles. Future studies of lichen distribution and productivity should take into account the recovery phenomena.     

Influence of sun irradiance and water availability on lichen photosynthetic pigments during a Mediterranean summer

This study was carried out to investigate changes in lichen photosynthetic pigments induced by different combinations of light irradiance and water availability during a Mediterranean summer. To this purpose, thalli of three epiphytic lichens with a markedly different ecology concerning photo-hygrophytism, namely Evernia prunastri (hygro-mesophytic), Flavoparmelia caperata (mesophytic) and Xanthoria parietina (xero-mesophytic), were transplanted for 30 days to N- and S-facing cardinal exposures in central Italy. To investigate the effect of thallus hydration, at each cardinal exposure 50% of thalli were hydrated daily with deionised water. The results showed that changes in the concentrations of photosynthetic pigments are species-specific and consist in a general depression of photosynthetic pigments only in the hygro-mesophytic species E. prunastri. The pattern of photosynthetic pigments was also investigated in spontaneous samples along contrasting aspects. In this case, X. parietina from S-facing slopes, adapted to direct solar influx, showed higher pigment content than N-facing thalli; F. caperata and E. prunastri avoid direct extreme solar radiation and assimilation pigments were influenced more by the shadowing of tree canopies than by the cardinal exposure. The influence of drought on lichen photosynthetic pigments in the Mediterranean area is discussed.     

Desiccation tolerance of the epilithic lichen Lecanora muralis (Schreb.) Rabenh. in the temperate climate

Lecanora muralis (Schreb.) Rabenh. is a ubiquitous epilithic crustose lichen of the temperate climate. It is well studied in terms of diel and annual carbon budget and productivity with continuous long-term observations in the field in 1995/96 by Otto L. Lange, Würzburg, and collaborators. However, these earlier studies left open the question to which extent the lichen is desiccation tolerant and if desiccation tolerance might possibly limit photosynthetic activity. In present study measurements of chlorophyll fluorescence parameters were performed to assess photosynthetic activity under various daily weather conditions throughout the year and recovery from desiccation after various periods of dryness in ambient air. Under any weather conditions, including strong frost for several days with night-temperatures around −15 °C and strong heat of several days with day-temperatures around 35 °C, the lichen was fully photosynthetically competent after wetting the samples for 15 min by submersion in water when they were dry in the field in the absence of actual incident precipitation. Chlorophyll fluorescence parameters were identical under all weather conditions sampled. A sample kept dry in ambient air for 37 days showed full recovery of chlorophyll fluorescence parameters after wetting for 30 min. Samples desiccated for longer periods up to 155 days took longer wetting times of about 300 min and recovered only partially but nevertheless showed active photosynthetic electron transport. Of 17 samples desiccated for 177–178 days only three recovered after rewetting for several days. It is concluded that the desiccation tolerance of L. muralis is sufficient to overcome dry spells of duration as it normally occurs in its natural environment. Desiccation tolerance is not likely to limit carbon budget and productivity.     

Photosynthesis of the cyanobacterial soil-crust lichen Collema tenax from arid lands in southern Utah, USA: role of water content on light and temperature responses of CO2 exchange

1. The gelatinous cyanobacterial Collema tenax is a dominant lichen of biotic soil crusts in the western United States. In laboratory experiments, we studied CO₂ exchange of this species as dependent on water content (WC), light and temperature. Results are compared with performance of green-algal lichens of the same site investigated earlier.
2. As compared with published data, photosynthetic capacity of C. tenax is higher than that of other cyanobacterial and green-algal soil-crust species studied. At all temperatures and photon flux densities of ecological relevance, net photosynthesis (NP) shows a strong depression at high degrees of hydration; maximal apparent quantum-use efficiency of CO₂ fixation is also reduced. Water requirements (moisture compensation point, WC for maximal NP) are higher than that of the green-algal lichens. Collema tenax exhibits extreme 'sun plant' features and is adapted to high thallus temperatures.
3. Erratic rain showers are the main source of moisture for soil crusts on the Colorado Plateau, quickly saturating the lichens with liquid water. High water-holding capacity of C. tenax ensures extended phases of favourable hydration at conditions of high light and temperature after the rain for substantial photosynthetic production. Under such conditions the cyanobacterial lichen appears superior over its green-algal competitors, which seem better adapted to habitats with high air humidity, dew or fog as prevailing source of moisture.     

PHENOTYPIC VARIATION WITHIN “INDIVIDUAL” LICHEN THALLI

“Individual” large diam lichen thalli of Umbilicaria vellea (L.) Ach. and U. mammulata (Ach.) Tuck. are not uniform in physiological activity or enzymatic phenotype. Horizontal variation in net photosynthetic rates and dark respiration rates was found, but this was independent of the mass of the photosynthesizing or respiring tissues. In addition, sublethal temperature pretreatments reduced the net photosynthetic and respiratory rates of some areas of the thallus, but increased others. Assays of isoenzyme phenotypes showed that all large diam thalli are extensively polymorphic while young, small diam thalli are mainly monomorphic. Taken together, the results say that the concept of the “individual” may be inappropriate for these organisms.     

Net photosynthetic response patterns of the basidiomycete lichen Cora pavonia (Web.) E. Fries from the tropical volcano La Soufrière (Guadeloupe)

Summary The response of net photosynthesis to temperature, moisture, and light was examined in thalli of the tropical basidiomycete lichen Cora pavonia from recent lahar flows on the volcanic summit La Soufrière (Guadeloupe, French West Indies). Although thalli of C. pavonia are typically exposed to only low light intensities and isothermal temperature conditions under prevailing cloud/shroud conditions on La Soufrière, their photosynthetic response matrix reveals an unexpected breadth of response. The temperature optimum of net photosynthetic uptake in C. pavonia rises from 6°C at a photon flux area density of 25 mol m^–2 s^–1 PAR to 27°C at 1000 mol m^–2 s^–1 PAR, with rates of maximal net photosynthetic uptake exceeding 25 mg CO₂ g^–1 h^–1. Net photosynthesis was optimal at thallus moisture contents of 250 to 350 percent water content by weight, declining only slightly in fully saturated thalli. These response patterns pose an apparent paradox, as on most days they will act to severely restrict net photosynthetic uptake by thalli of C. pavonia on La Soufrière. This paradox is discussed in context of those selective pressures faced by lichen thalli in later successional stages as well as those imposed by brief periods of atypical weather conditions.     

The effects of climatic pattern on lichen productivity: Cetraria cucullata (Bell.) Ach. in the arctic tundra of northern Alaska

Summary The climatic control of productivity for two populations of the lichen Cetraria cucullata (Bell.) Ach. growing in the arctic tundra of northern Alaska (70°28N, 157°23W) was examined. Respiratory losses of carbon vary with tissue temperature, tissue water content, and time since wetting. Potential net photosynthetic gains of carbon are affected by photon flux density, tissue temperature, and water content. The net CO₂ exchange responses of populations growing on ridge tundra and on upland tundra differ and these differences reflect possible adaptation to the normal environmental regimes in the two habitats. Simulation of the lichen's net carbon balance using continuous hourly records of photon flux density, temperature, and water content for the unusually dry period June 28 through July 17, 1977 show that lichen biomass is actually lost during climatic regimes leading to frequent but short periods of lichen metabolic activity. This result is confirmed by the negative relative growth rates measured for C. cucullata over the same monitoring period. This observed loss of biomass may be attributable to depletion of carbon reserves to reactivate dormant metabolism without sufficiently long periods favorable for net photosynthetic activity to replenish the lost reserves. These results illustrate that environmental limits exist on the success of the dormancy strategy characteristic of lichen and moss carbon metabolism.     

Chlorophyll a Fluorescence Emission,Xanthophyll Cycle Activity,and Net Photosynthetic Rate Responses to Ozone in Some Foliose and Fruticose Lichen Species

The lichens Parmelia quercina, Parmelia sulcata, Evernia prunastri, Hypogymnia physodes, and Anaptychia ciliaris were exposed to ozone (O₃) in controlled environment cuvettes designed to maintain the lichens at optimal physiological activity during exposure. Measurements of gas exchange, modulated chlorophyll (Chl) fluorescence, and pigment analysis were conducted before and after exposure to 300 mm³ (O₃) m^–3, 4 h per d for 14 d. No changes in the efficiency of photosystem 2 (PS2) photochemistry, the reduction state of Q_A, or the electron flow through PS2, measured by Chl fluorescence, were detected in any of the five lichen species studied. Additionally, neither photosynthetic CO₂ assimilation nor xanthophyll cycle activity or photosynthetic pigment concentration were affected by high O₃ concentrations. Thus the studied lichen species have significant capacities to withstand oxidative stresses induced by high concentration of O₃.     

Does the lichen mat alleviate the effects of wet deposited nickel on soil microorganisms and Scots pine (Pinus sylvestris L.) seedlings?

A field experiment was conducted in a dry heath forest dominated by Scots pine (Pinus sylvestris L.) and a mat-forming lichen (Cladina stellaris (Opiz) Brodo) to assess the effect of wet-deposited nickel (Ni) on pine seedlings and soil microorganisms, and to explore whether an intact lichen mat could act as a buffer against heavy metal deposits. Pine seedlings were planted in quadrats covered by a natural lichen layer and in quadrats from which the lichen layer had been completely removed. The quadrats were exposed to four levels of Ni deposition: 0 (i.e., distilled water), 10, 100 and 1000 mg m^–2 year^–1 in two growing seasons. Increasing Ni deposition led to an increase in the Ni content of the needles, roots and the soil organic layer. The lichen mat reduced Ni flow to the organic soil layer, but had no significant, reducing effect on needle or root Ni concentration. The most severe Ni treatment had detrimental effects on seedling growth and increased peroxidase activity in the previous years needles. Removal of the lichen layer did not increase susceptibility of seedlings to Ni. Values of maximal carbon use efficiency (Max) and metabolic quotient (qCO₂) of the soil microorganisms indicated protective value of the lichen mat to soil microorganisms at the highest Ni treatment. Skimming per se decreased basal respiration, qCO₂ and concentrations of potassium in the soil and also increased the lag period of the microorganisms as a response to in situ substrate addition.     

PHOTOSYNTHETIC CHARACTERIZATION OF DEVELOPING AND MATURE AKINETES OF APHANIZOMENON OVALISPORUM (CYANOPROKARYOTA)1

Akinetes, differentiated resting cells produced by many species of filamentous, heterocystous cyanobacteria, enable the organism to survive adverse conditions, such as cold winters and dry seasons, and to maintain germination capabilities until the onset of suitable conditions for vegetative growth. Mature akinetes maintain a limited level of metabolic activities, including photosynthesis. In the present study, we have characterized changes in the photosynthetic apparatus of vegetative cells and akinetes of the cyanobacterium Aphanizomenon ovalisporum Forti (Nostocales) during their development and maturation. Photosynthetic variable fluorescence was measured by microscope‐PAM (pulse‐amplitude‐modulated) fluorometry, and the fundamental composition of the photosynthetic apparatus was evaluated by fluorescence and immunological techniques. Vegetative cells and akinetes from samples of Aphanizomenon trichomes from akinete‐induced cultures at various ages demonstrated a gradual reduction, with age, in the maximal photosynthetic quantum yield in both cell types. However, the maximal quantum yield of akinetes declined slightly faster than that of their adjacent vegetative cells. Mature akinetes isolated from 6‐ to 8‐week‐old akinete‐induced cultures maintained only residual photosynthetic activity, as indicated by very low values of maximal photosynthetic quantum yields. Based on 77 K fluorescence emission data and immunodetection of PSI and PSII polypeptides, we concluded that the ratio of PSI to PSII reaction centers in mature akinetes is slightly higher than the ratio estimated for exponentially grown vegetative cells. Furthermore, the cellular abundance of these protein complexes substantially increased in akinetes relative to exponentially grown vegetative cells, presumably due to considerable increase in the biovolume of akinetes.     

Carbon dioxide exchange of Antarctic crustose lichens in situ measured with a CO2/H2O porometer

Summary Photosynthesis and respiration of crustose lichens in their natural situation were measured by means of a Walz porometer with a modified cuvette and a plexiglass ring. Habitat influence and the specific performance of three maritime Antarctic species were demonstrated by diurnal courses of microclimate and CO₂ exchange during rainy days. In further field experiments the photosynthetic response to soaking with water was tested. Haematomma erythromma is rain-exposed at its natural habitat on coastal rocks but tends to dry out quickly. The photosynthetic efficiency of the chlorophyll of this photophilous species was high. Lecidea sciatrapha appears to be chionophilous and had a low light compensation point of its net photosynthesis. The photosynthetic rates per surface area of these two species were low compared with those of Caloplaca sublobulata. According to its habitat selection C. sublobulata is typified as an ombrophobous lichen. This characterization was confirmed experimentally by our gas exchange measurements.     

Non-invasive monitoring of photosynthetic activity and water content in forest lichens by spectral reflectance data and RGB colors from photographs

There is a need for non-invasive monitoring of temporal and spatial variation in hydration and photosynthetic activity of red-listed poikilohydric autotrophs. Here, we simultaneously recorded kinetics in RGB-colors (photos), reflectance spectra, water content, maximal (F_V/F_M), and effective quantum yield of PSII (Φ_PSII) during desiccation in foliose lichens differing in cortical characteristics and photobionts. The spectral absorbance peaks of chlorophyll a, phycocyanin, and phycoerythrin were clearly displayed at high hydration levels. Brightness and total RGB colors of the lichens strongly increased during desiccation. The normalized difference vegetation index (NDVI) efficiently estimated hydration level and Φ_PSII – a proxy for lichen photosynthesis – in all species, including threatened old forest lichens. Color and reflectance indices based on green wavelengths gave good estimates of water content in cephalo- and chlorolichens, but not in cyanolichens with a wider range of photosynthetic pigments. Due to species-specific characteristics, species-wise calibration is essential for non-invasive assessments of lichen functioning.     

New Insights into the Biological Activity of Lichens: Bioavailable Secondary Metabolites of Umbilicaria decussata as Potential Anticoagulants

This study reports the in vitro anticoagulation activity of acetonic extract (AE) of 42 lichen species and the identification of potential bioavailable anticoagulant compounds from Umbilicaria decussata as a competent anticoagulant lichen species. Lichens’ AEs were evaluated for their anticoagulant activity by monitoring activated partial thromboplastin time (APTT) and prothrombin time (PT) assays. A strong, positive correlation was observed between total phenolics concentration (TPC) of species and blood coagulation parameters. U. decussata was the only species with the longest clotting time in both APTT and PT assays. The research was moved forward by performing in vivo assays using rats. The results corroborated the dose-dependent impact of U. decussata’s AE on rats’ clotting time. Major secondary metabolites of U. decussata and their plasma-related bioavailability were also investigated using LC-ESI-MS/MS. Atranol, orsellinic acid, D-mannitol, lecanoric acid, and evernic acid were detected as possible bioavailable anticoagulants of U. decussata. Our findings suggest that U. decussata might be a potential anticoagulant lichen species that can be used for the prevention or treatment of coagulation-related issues such as cardiovascular diseases (CVDs).