Photorespiration in eelgrass (Zostera marina L.): A photoprotection mechanism for survival in a CO2-limited world

• Published in: Frontiers in Plant Science
• Main Authors: Celebi-Ergin, Billur, Zimmerman, Richard C., Hill, Victoria J.
• Other Authors: National Science Foundation, Virginia Sea Grant, Virginia Institute of Marine Science, Old Dominion University
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Frontiers Media SA 2022
• Subjects: Plant Science; Ocean acidification
• Online Access: http://dx.doi.org/10.3389/fpls.2022.1025416; https://www.frontiersin.org/articles/10.3389/fpls.2022.1025416/full

Photorespiration, commonly viewed as a loss in photosynthetic productivity of C3 plants, is expected to decline with increasing atmospheric CO 2 , even though photorespiration plays an important role in the oxidative stress responses. This study aimed to quantify the role of photorespiration and alternative photoprotection mechanisms in Zostera marina L. (eelgrass), a carbon-limited marine C3 plant, in response to ocean acidification. Plants were grown in controlled outdoor aquaria at different [CO 2 ] aq ranging from ~55 (ambient) to ~2121 μ M for 13 months and compared for differences in leaf photochemistry by simultaneous measurements of O 2 flux and variable fluorescence. At ambient [CO 2 ], photosynthesis was carbon limited and the excess photon absorption was diverted both to photorespiration and non-photochemical quenching (NPQ). The dynamic range of NPQ regulation in ambient grown plants, in response to instantaneous changes in [CO 2 ] aq , suggested considerable tolerance for fluctuating environmental conditions. However, 60 to 80% of maximum photosynthetic capacity of ambient plants was diverted to photorespiration resulting in limited carbon fixation. The photosynthesis to respiration ratio ( P E : R D ) of ambient grown plants increased 6-fold when measured under high CO 2 because photorespiration was virtually suppressed. Plants acclimated to high CO 2 maintained 4-fold higher P E : R D than ambient grown plants as a result of a 60% reduction in photorespiration. The O 2 production efficiency per unit chlorophyll was not affected by the CO 2 environment in which the plants were grown. Yet, CO 2 enrichment decreased the light level to initiate NPQ activity and downregulated the biomass specific pigment content by 50% and area specific pigment content by 30%. Thus, phenotypic acclimation to ocean carbonation in eelgrass, indicating the coupling between the regulation of photosynthetic structure and metabolic carbon demands, involved the downregulation of light harvesting by the photosynthetic ...