Solhaug Knut Asbjørn, Gauslaa Yngvar
Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, P. O. Box 5003, NO-1432, Ås, Norway.
Planta. 2025 May 22;262(1):3. doi: 10.1007/s00425-025-04720-2.
Hair lichen photoprotection involves algal and fungal strategies while hydrated, with pale lichens compensating weak fungal cortical pigments through high, rapidly induced non-photochemical quenching by the photobiont. Hair lichens play vital roles in boreal forests by influencing nutrient cycles, microclimates, and providing habitats for invertebrates and forage for animals. This study examines two widespread and dominant species, Bryoria fuscescens and Alectoria sarmentosa, which possess different fungal pigments-dark light-absorbing melanin in Bryoria, and pale reflecting usnic acid in Alectoria. These cortical pigments affect species distribution, with Bryoria favoring sun-exposed forest canopies due to its efficient light-protective melanin, while Alectoria thrives in partly shaded, moist environments. By investigating sympatric populations, we explored whether non-photochemical quenching (NPQ) compensates for Alectoria's less-effective sun-screening pigment. Our results reveal that Alectoria exhibits higher and more rapidly induced NPQ compared to Bryoria, along with faster recovery from photoinhibition. The flexibility and rapid response of Alectoria's NPQ help mitigate high-light stress, optimizing growth in fluctuating light environments. These compensatory mechanisms suggest that, despite weaker cortical pigmentation, hydrated Alectoria can sustain photosynthesis and recover from light-induced damage more efficiently. However, because NPQ does not function in the desiccated state-where efficient sun-screening by cortical pigments is essential-Alectoria is confined to humid and sheltered forest canopies in drier macroclimates but not in rainforest climates. This study underscores the adaptive strategies of both photobionts and mycobionts in hydrated hair lichens to manage varying light conditions in boreal forests, highlighting NPQ as a compensating mechanism in lichen photoprotection. It advances our understanding by illustrating how the transition from dry to wet conditions amplifies the algal partner's contribution to overall photoprotection.
毛发地衣的光保护涉及水合状态下藻类和真菌的策略，浅色地衣通过共生光合生物快速诱导产生的高水平非光化学猝灭来补偿真菌皮层色素的不足。毛发地衣通过影响养分循环、微气候，为无脊椎动物提供栖息地以及为动物提供食物，在北方森林中发挥着至关重要的作用。本研究考察了两种广泛分布且占主导地位的物种，即褐苔草（Bryoria fuscescens）和长松萝（Alectoria sarmentosa），它们具有不同的真菌色素——褐苔草中含有深色吸光的黑色素，而长松萝中含有浅色的反光松萝酸。这些皮层色素影响物种分布，褐苔草因其高效的光保护黑色素而偏好阳光照射的森林树冠，而长松萝则在部分遮荫、潮湿的环境中茁壮成长。通过研究同域种群，我们探究了非光化学猝灭（NPQ）是否能弥补长松萝防晒色素效果较差的问题。我们的结果表明，与褐苔草相比，长松萝表现出更高且诱导更快的NPQ，同时从光抑制中恢复得更快。长松萝NPQ的灵活性和快速响应有助于减轻高光胁迫，在波动的光照环境中优化生长。这些补偿机制表明，尽管皮层色素沉着较弱，但水合状态下的长松萝能够更有效地维持光合作用并从光诱导损伤中恢复。然而，由于NPQ在干燥状态下不起作用——此时皮层色素的有效防晒至关重要——长松萝在较干燥的大气候中仅限于潮湿且有遮蔽的森林树冠，而在雨林气候中则不然。本研究强调了水合毛发地衣中共生光合生物和真菌共生体在应对北方森林中不同光照条件时的适应性策略，突出了NPQ作为地衣光保护中的一种补偿机制。它通过说明从干燥到湿润条件的转变如何增强藻类伙伴对整体光保护的贡献，推进了我们的理解。
