The role of irradiance and C-use strategies in tropical macroalgae photosynthetic response to ocean acidification.

Fleshy macroalgae may increase photosynthesis with greater CO availability under ocean acidification (OA) and outcompete calcifying macroalgae important for tropical reef accretion. Macroalgae use energy-dependent carbon concentrating mechanisms (CCMs) to take up HCO, the dominant inorganic carbon for marine photosynthesis, but carbon-use strategies may depend on the pCO, pH and irradiance. We examined photosynthesis in eight tropical macroalgae across a range of irradiances (0-1200 μmol photon m s), pH levels (7.

Climate change and ocean acidification effects on seagrasses and marine macroalgae.

Although seagrasses and marine macroalgae (macro-autotrophs) play critical ecological roles in reef, lagoon, coastal and open-water ecosystems, their response to ocean acidification (OA) and climate change is not well understood. In this review, we examine marine macro-autotroph biochemistry and physiology relevant to their response to elevated dissolved inorganic carbon [DIC], carbon dioxide [CO2 ], and lower carbonate [CO3 (2-) ] and pH. We also explore the effects of increasing temperature under climate change and the interactions of elevated temperature and [CO2 ].

Characterization of the NADP malic enzyme gene family in the facultative, single-cell C4 monocot Hydrilla verticillata.

Hydrilla verticillata has a facultative single-cell system that changes from C3 to C4 photosynthesis. A NADP+-dependent malic enzyme (NADP-ME) provides a high [CO2] for Rubisco fixation in the C4 leaf chloroplasts. Of three NADP-ME genes identified, only hvme1 was up-regulated in the C4 leaf, during the light period, and it possessed a putative transit peptide.

Light regulation of the photosynthetic phosphoenolpyruvate carboxylase (PEPC) in Hydrilla verticillata.

The submersed monocot, Hydrilla verticillata (L.f.) Royle, is a facultative C(4) NADP-malic enzyme (NADP-ME) plant in which the C(4) and Calvin cycles co-exist in the same cell.

Identification of C4 responsive genes in the facultative C4 plant Hydrilla verticillata.

The aquatic monocot Hydrilla verticillata (L.f.) Royle is a well-documented facultative C4 NADP-malic enzyme species in which the C4 and Calvin cycles operate in the same cell with the specific carboxylases confined to the cytosol and chloroplast, respectively.

Photosynthetic and other phosphoenolpyruvate carboxylase isoforms in the single-cell, facultative C(4) system of Hydrilla verticillata.

The submersed monocot Hydrilla verticillata (L.f.) Royle is a facultative C(4) plant.

C4 mechanisms in aquatic angiosperms: comparisons with terrestrial C4 systems.

Aquatic C4 photosynthesis probably arose in response to dissolved CO2 limitations, possibly before its advent in terrestrial plants. Of over 7600 C4 species, only about a dozen aquatic species are identified. Amphibious Eleocharis species (sedges) have C3-C4 photosynthesis and Kranz anatomy in aerial, but not submersed, leaves.