Photosynthesis and Metabolism of Seagrasses

Anthony W. D. Larkum (Lead / Corresponding author), Mathieu Pernice, Martin Schliep, Peter Davey, Milan Szabo, John A. Raven, Mads Lichtenberg, Kasper Elgetti Brodersen, Peter J. Ralph

    Research output: Chapter in Book/Report/Conference proceedingChapter

    2 Citations (Scopus)

    Abstract

    Seagrasses have a unique leaf morphology where the major site for chloroplasts is in the epidermal cells, stomata are absent and aerenchyma is present inside the epidermis. This means that the major site for photosynthesis is in the epidermis. Furthermore the lack of stomata means that the route for carbon uptake is via inorganic carbon (Ci) uptake across the vestigial cuticle and through the outer plasma membranes. Since the leaf may at times be in an unstirred situation diffusion through an unstirred layer outside the leaf may be a large obstacle to carbon uptake. The existence of a carbon concentrating mechanism is discussed, but its existence to date is not proven. Active bicarbonate uptake across the plasmalemma does not seem to operate; an external carbonic anhydrase and an extrusion of protons seem to play a role in enhancing CO2 uptake. There is some evidence that a C4 mechanism plays a role in carbon fixation but more evidence from “omics” is required. Photorespiration certainly occurs in seagrasses and an active xanthophyll cycle is present to cope with damaging high light, but both these biochemical mechanisms need further work. Finally, epiphytes pose a problem which impedes the uptake of Ci and modifies the light environment inside the leaves.
    Original languageEnglish
    Title of host publicationSeagrasses of Australia
    Subtitle of host publicationStructure, Ecology and Conservation
    EditorsAnthony W. D. Larkum, Gary A. Kendrick, Peter J. Ralph
    Place of PublicationSwitzerland
    PublisherSpringer International Publishing
    Pages315-342
    Number of pages28
    ISBN (Electronic)9783319713540
    ISBN (Print)9783319713526
    DOIs
    Publication statusPublished - 2018

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