Nemcova Y, Neustupa J, Pichrtová M
Department of Botany, Charles University, Benatska 2, 128 00, Prague 2, Czech Republic.
Protoplasma. 2025 Apr 3. doi: 10.1007/s00709-025-02061-1.
Desmids are valuable bioindicators in peatland ecosystems due to their sensitivity to environmental changes. In temperate and boreal wetlands, seasonal desiccation of aquatic habitats, which is increasing in frequency and severity due to ongoing climate change, is currently considered a key factor structuring the distribution of individual taxa. In this study, the desiccation tolerance of Micrasterias thomasiana and Staurastrum hirsutum isolated from contrasting hydrological environments in the peatland habitats of the Ore Mountains, Czech Republic, is investigated. Using controlled experimental conditions, we subjected both young, actively growing and old, mature cultures to four different desiccation treatments and evaluated morphology and photosynthetic performance. Our results showed that young and old cultures of both species exhibited a very similar photophysiological response. Severe desiccation led to an irreversible decline in the effective quantum yield of photosystem II in both species, resulting in cell death. Mild drought stress allowed the cultures to recover, indicating that the stress severity determines the recovery potential. Finally, prolonged desiccation resulted in irreversible damage in older cultures of both species, emphasizing the limited desiccation resilience of desmids. We observed similarities in morphology with Zygnema "pre-akinetes," but in contrast to these resilient cells, the old cells of M. thomasiana and S. hirsutum did not survive the harsher desiccation conditions. Long-term mild desiccation revealed a higher resistance of S. hirsutum, probably due to the protective role of its dense mucilage. In nature, these two species usually inhabit localities with low desiccation risk or avoid and mitigate desiccation stress through localized survival strategies.
由于对环境变化敏感，鼓藻类是泥炭地生态系统中有价值的生物指示物种。在温带和北方湿地，由于气候变化，水生栖息地的季节性干燥频率和严重程度不断增加，目前被认为是影响单个分类单元分布的关键因素。在本研究中，我们调查了从捷克共和国厄尔士山脉泥炭地栖息地不同水文环境中分离出的托马斯微星鼓藻（Micrasterias thomasiana）和多毛十字鼓藻（Staurastrum hirsutum）的耐旱性。在可控实验条件下，我们对年轻、生长活跃的培养物和年老、成熟的培养物进行了四种不同的干燥处理，并评估了形态和光合性能。我们的结果表明，两个物种的年轻和年老培养物都表现出非常相似的光生理反应。严重干燥导致两个物种光系统II的有效量子产率不可逆下降，导致细胞死亡。轻度干旱胁迫使培养物能够恢复，这表明胁迫严重程度决定了恢复潜力。最后，长时间干燥导致两个物种的年老培养物出现不可逆损伤，强调了鼓藻类有限的干燥恢复能力。我们观察到它们在形态上与双星藻属“前厚壁孢子”相似，但与这些有恢复能力的细胞不同，托马斯微星鼓藻和多毛十字鼓藻的老细胞在更严酷的干燥条件下无法存活。长期轻度干燥显示多毛十字鼓藻具有更高的抗性，这可能归因于其致密黏液的保护作用。在自然环境中，这两个物种通常栖息在干燥风险较低的地方，或者通过局部生存策略避免和减轻干燥胁迫。
