Green algae are major components of biological soil crusts in alpine habitats. Together with cyanobacteria, fungi and lichens, green algae form a pioneer community important for the organisms that will succeed them. In their high altitudinal habitat these algae are exposed to harsh and strongly fluctuating environmental conditions, mainly intense irradiation, including ultraviolet radiation, and lack of water leading to desiccation. Therefore, green algae surviving in these environments must have evolved with either avoidance or protective strategies, as well as repair mechanisms for damage. In this review we have highlighted these mechanisms, which include photoprotection, photochemical quenching, and high osmotic values to avoid water loss, and in some groups flexibility of secondary cell walls to maintain turgor pressure even in water-limited situations. These highly specialized green algae will serve as good model organisms to study desiccation tolerance or photoprotective mechanisms, due to their natural capacity to withstand unfavorable conditions. We point out the urgent need for modern phylogenetic approaches in characterizing these organisms, and molecular methods for analyzing the metabolic changes involved in their adaptive strategies.

中文翻译：

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高山生物土壤结皮群落中的绿藻：抗紫外线辐射和脱水的适应策略。

绿藻是高山栖息地生物土壤结皮的主要成分。与蓝细菌、真菌和地衣一起，绿藻形成了一个先驱群落，对于将要继承它们的生物来说非常重要。在它们的高海拔栖息地，这些藻类暴露在恶劣和剧烈波动的环境条件下，主要是强烈的辐射，包括紫外线辐射，以及导致干燥的缺水。因此，在这些环境中存活的绿藻必须通过避免或保护策略以及损伤修复机制进化。在这篇综述中，我们强调了这些机制，包括光保护、光化学猝灭和高渗透值以避免水分流失，并且在某些组中，次生细胞壁的灵活性即使在水有限的情况下也能保持膨胀压力。这些高度专业化的绿藻将成为研究干燥耐受性或光保护机制的良好模式生物，因为它们具有承受不利条件的天然能力。我们指出迫切需要现代系统发育方法来表征这些生物，以及分析其适应策略中涉及的代谢变化的分子方法。