The contribution of aerenchymal CO2 to the photosynthesis of emergent and submerged culms of Scirpus lacustris and Cyperus papyrus

Alon Singer*, Amram Eshel, Moshe Agami, Sven Beer

*Corresponding author for this work

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14 Scopus citations

Abstract

In this work it was investigated whether sediment-derived aerenchymal CO2 could be utilized for photosynthesis in the culms of the two emergent aquatic macrophytes Scirpus lacustris L. (a C3 plant) and Cyperus papyrus L. (a C4 plant). Aerenchymal CO2 concentrations within the submerged parts of the culms were found to be 30 000-50 000 μl l-1, and ca. 800 μl l-1 in the emergent parts of Scirpus lacustris and 2000 μl l-1 in Cyperus papyrus. These concentrations tended to be lower during the day in Cyperus, while no clear diurnal pattern was observed for Scirpus. Photosynthetic rates based on fixation of external or internal CO2 were measured in situ by providing 14CO2 either externally or from the aerenchyma (by supplying 14C-labelled CO2 through test-tubes attached to excised culms). The results showed that the contribution of aerenchymal CO2 to the total photosynthesis of emergent culms was less than 0.25% in both species. This has a rationale in that photosynthetic rates of both species were saturated at the ambient air CO2 concentration, but it remains unclear why CO2 does not diffuse towards the photosynthesizing tissues. By contrast, internal CO2 appeared to be the only source of inorganic carbon used for photosynthesis of young submerged green culms. It is thus suggested that the aerenchyma, in addition to other functions, is important in providing sediment-derived CO2 for photosynthesis in young shoots or culms if growing submerged, before they reach the water surface.

Original languageEnglish
Pages (from-to)107-116
Number of pages10
JournalAquatic Botany
Volume49
Issue number2-3
DOIs
StatePublished - Aug 1994

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