Water relations and photosystem II efficiency of the intertidal macroalga Fucus virsoides

• Published in: Plant physiology and biochemistry Vol. 215; p. 109000
• Main Authors: Descourvières, Emmanuelle, Petruzzellis, Francesco, Falace, Annalisa, Nardini, Andrea, Tomasella, Martina
• Format: Journal Article
• Language: English
• Published: France Elsevier Masson SAS 01-10-2024
• Subjects: Capacitance; Fucus virsoides; Modulus of elasticity; Photosystem II efficiency; Pressure-volume curves; Turgor loss point; Photosystem II efficiency; Capacitance; Modulus of elasticity; Fucus virsoides; Pressure-volume curves; Turgor loss point
• ISSN: 0981-9428; 1873-2690; 1873-2690
• DOI: 10.1016/j.plaphy.2024.109000

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 (Fv/Fm) 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 (Ψtlp, -7.0 MPa on average), and the maintenance of high Fv/Fm at low water potentials indicating a prolonged maintenance of healthy physiological status. While no differences were observed between growth stages, Ψtlp, 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 Ψtlp, 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.
•We assessed pressure-volume curves and photosystem II efficiency in Fucus virsoides.•F. virsoides showed remarkably low water potentials at turgor loss point (−7 MPa).•Photosystem II efficiency was maintained relatively high at low water potentials.•Water potentials after a typical prolonged emersion overcame the turgor loss point.•Frequent emersions under a harsher climate might be involved in the species’ decline.