Department of Life Sciences, University of Trieste, Via L. Giorgieri 10, 34127 Trieste, Italy; National Institute of Oceanography and Applied Geophysics - OGS, Via Beirut 2, 34014 Trieste, Italy.
Department of Life Sciences, University of Trieste, Via L. Giorgieri 10, 34127 Trieste, Italy.
Plant Physiol Biochem. 2024 Oct;215:109000. doi: 10.1016/j.plaphy.2024.109000. Epub 2024 Jul 31.
Intertidal macroalgae are sessile poikilohydric organisms exposed to desiccation stress during emersion. Water relations parameters are useful tools to evaluate an organism's capacity to withstand water scarcity conditions, but such information on marine intertidal macroalgae is scarce. We assessed the water relations of the intertidal relict Fucus virsoides, the unique Fucus species endemic to the Mediterranean. We combined measurements of water potential (Ψ) parameters derived from pressure-volume curves and chlorophyll a fluorescence (F/F) in juvenile and adult thalli sampled in three different dates between March and April 2023. F. virsoides exhibited remarkable water stress tolerance, as evidenced by the low water potential at turgor loss point (Ψ, -7.0 MPa on average), and the maintenance of high F/F at low water potentials indicating a prolonged maintenance of healthy physiological status. While no differences were observed between growth stages, Ψ, capacitance (C) and the bulk modulus of elasticity (ε) varied significantly according to the sampling dates, whereas the osmotic potential at full turgor did not significantly change. Ψ measured on thalli collected after a typical prolonged emersion period was markedly lower (-12.3 MPa on average) than the estimated Ψ, suggesting that the population is frequently undergoing turgor loss. Further investigations are required to determine environmental tolerance ranges based on water status characteristics to enhance our understanding of F. virsoides responses and vulnerability to climate change, thus providing insight into the possible causes of its widespread decline.
潮间带大型藻类是固着的变渗生物，在暴露于空气中时会受到干燥胁迫。水分关系参数是评估生物体耐受缺水条件能力的有用工具，但有关海洋潮间带大型藻类的此类信息很少。我们评估了潮间带遗迹性墨角藻（Fucus virsoides）的水分关系，墨角藻是地中海特有的唯一的墨角藻物种。我们结合了 2023 年 3 月至 4 月期间三个不同日期采集的幼体和成年藻体的压力-体积曲线和叶绿素 a 荧光（F/F）测量值来推导水分参数。F. virsoides 表现出显著的水分胁迫耐受能力，这表现在其膨压损失点的低水分势（平均为-7.0 MPa），以及在低水分势下保持高 F/F 表明健康生理状态的延长维持。虽然在生长阶段之间没有观察到差异，但水分势、电容（C）和弹性模量（ε）根据采样日期有显著变化，而充分膨压下的渗透势没有显著变化。在典型的长时间暴露后采集的藻体的 Ψ 测量值明显较低（平均为-12.3 MPa），这表明该种群经常经历膨压损失。需要进一步的调查来确定基于水分状况特征的环境耐受范围，以增强我们对 F. virsoides 响应和对气候变化脆弱性的理解，从而深入了解其广泛下降的可能原因。
