High-light damage in air-dry thalli of the old forest lichen Lobaria pulmonaria--interactions of irradiance, exposure duration and high temperature

Gauslaa, Yngvar; Solhaug, Knut Asbjørn

doi:10.1093/jxb/50.334.697

Cited by 66 publications

(90 citation statements)

References 9 publications

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“…Thus, dark Bryoria species are heated and can melt the snow in tree canopies during winter and thus cause hydration and activation of photosynthesis (Coxson and Coyle 2003). Some melanic lichens are susceptible to heating by excess light (Gauslaa and Solhaug 1999). This may explain why some large melanic lichen genera such as Bryoria (Brodo and Hawksworth 1977) and Melanelia (Esslinger 1977) are restricted to cool-cold climates.…”

Section: Discussionmentioning

confidence: 99%

Sunscreening fungal pigments influence the vertical gradient of pendulous lichens in boreal forest canopies

Färber

Solhaug

Esseen

et al. 2014

Ecology

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Abstract. Pendulous lichens dominate canopies of boreal forests, with dark Bryoria species in the upper canopy vs. light Alectoria and Usnea species in lower canopy. These genera offer important ecosystem services such as winter forage for reindeer and caribou. The mechanism behind this niche separation is poorly understood. We tested the hypothesis that species-specific sunscreening fungal pigments protect underlying symbiotic algae differently against high light, and thus shape the vertical canopy gradient of epiphytes. Three pale species with the reflecting pigment usnic acid (Alectoria sarmentosa, Usnea dasypoga, U. longissima) and three with dark, absorbing melanins (Bryoria capillaris, B. fremontii, B. fuscescens) were compared. We subjected the lichens to desiccation stress with and without light, and assessed their performance with chlorophyll fluorescence. Desiccation alone only affected U. longissima. By contrast, light in combination with desiccation caused photoinhibitory damage in all species. Usnic lichens were significantly more susceptible to light during desiccation than melanic ones. Thus, melanin is a more efficient light-screening pigment than usnic acid. Thereby, the vertical gradient of pendulous lichens in forest canopies is consistent with a shift in type and functioning of sunscreening pigments, from high-light-tolerant Bryoria in the upper to susceptible Alectoria and Usnea in the lower canopy.

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Section: Discussionmentioning

confidence: 99%

Sunscreening fungal pigments influence the vertical gradient of pendulous lichens in boreal forest canopies

Färber

Solhaug

Esseen

et al. 2014

Ecology

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“…This is manifested by a reduction in growth rates and reduced photosynthesis (Scheidegger et al, 1995;Bukhov, 2004). Lichens are often found growing on exposed rocks or trees, where they may face high levels of irradiation while in the desiccated state (Gauslaa and Solhaug, 1999). This is particularly problematic as it has high potential to be damaging to the photosynthetic apparatus of the photobiont under conditions where metabolic activities, including repair mechanisms, are shut down (Gauslaa and Solhaug, 1999).…”

mentioning

confidence: 99%

Photoprotection in the Lichen Parmelia sulcata: The Origins of Desiccation-Induced Fluorescence Quenching

et al. 2007

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Lichens, a symbiotic relationship between a fungus (mycobiont) and a photosynthetic green algae or cyanobacteria (photobiont), belong to an elite group of survivalist organisms termed resurrection species. When lichens are desiccated, they are photosynthetically inactive, but upon rehydration they can perform photosynthesis within seconds. Desiccation is correlated with both a loss of variable chlorophyll a fluorescence and a decrease in overall fluorescence yield. The fluorescence quenching likely reflects photoprotection mechanisms that may be based on desiccation-induced changes in lichen structure that limit light exposure to the photobiont (sunshade effect) and/or active quenching of excitation energy absorbed by the photosynthetic apparatus. To separate and quantify these possible mechanisms, we have investigated the origins of fluorescence quenching in desiccated lichens with steady-state, low temperature, and time-resolved chlorophyll fluorescence spectroscopy. We found the most dramatic target of quenching to be photosystem II (PSII), which produces negligible levels of fluorescence in desiccated lichens. We show that fluorescence decay in desiccated lichens was dominated by a short lifetime, long-wavelength component energetically coupled to PSII. Remaining fluorescence was primarily from PSI and although diminished in amplitude, PSI decay kinetics were unaffected by desiccation. The long-wavelength-quenching species was responsible for most (about 80%) of the fluorescence quenching observed in desiccated lichens; the rest of the quenching was attributed to the sunshade effect induced by structural changes in the lichen thallus.

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“…This decrease is likely associated with their phototolerance and could be caused by structural changes in the thallus that induce changes in light-scattering and shading properties or by changes in shape and aggregation of algae (de los Rios et al, 2007;Scheidegger et al, 1995;Veerman et al, 2007). The thallus also offers some protection against photodamage through the use of light-absorbing pigments (Gauslaa & Solhaug, 1999;Holder et al, 2000). All this kind of features decreases the exposure of the photosynthetic apparatus of the photobiont to light and can be described as sunshade mechanisms (Veerman et al, 2007).…”

Section: Mechanisms Of Light Energy Dissipation In Lichen Algaementioning

confidence: 99%

Photosynthesis in Lichen: Light Reactions and Protective Mechanisms

Gasulla¹,

Herrero²,

Esteban³

et al. 2012

Advances in Photosynthesis - Fundamental Aspects

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High-light damage in air-dry thalli of the old forest lichen Lobaria pulmonaria--interactions of irradiance, exposure duration and high temperature

Cited by 66 publications

References 9 publications

Sunscreening fungal pigments influence the vertical gradient of pendulous lichens in boreal forest canopies

Sunscreening fungal pigments influence the vertical gradient of pendulous lichens in boreal forest canopies

Photoprotection in the Lichen Parmelia sulcata: The Origins of Desiccation-Induced Fluorescence Quenching

Photosynthesis in Lichen: Light Reactions and Protective Mechanisms

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