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Biochemical and biophysical CO2 concentrating mechanisms in two species of freshwater macrophyte within the genus Ottelia (Hydrocharitaceae)

Zhang, Yizhi; Yin, Liyan; Jiang, Hong-Sheng; Li, Wei; Gontero, Brigitte; Maberly, Stephen C.. 2014 Biochemical and biophysical CO2 concentrating mechanisms in two species of freshwater macrophyte within the genus Ottelia (Hydrocharitaceae). Photosynthesis Research, 121 (2-3). 285-297. https://doi.org/10.1007/s11120-013-9950-y

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Abstract/Summary

Two freshwater macrophytes, Ottelia alismoides and Ottelia acuminata, were grown at low (mean 5 µmol L-1) and high (mean 400 µmol L-1) CO2 concentrations under natural conditions. The ratio of PEPC to RubisCO was 1.8 in O. acuminata in both treatments. In O. alismoides, this ratio was 2.8 and 5.9 when grown at high and low CO2, respectively, as a result of a 2-fold increase of PEPC activity. The activity of PPDK was similar to and changed in-line with PEPC (1.9-fold change). The activity of the decarboxylating NADP-malic enzyme (ME) was very low in both species while NAD-ME activity was high and increased with PEPC activity in O. alismoides. These results suggest that O. alismoides might perform a type of C4 metabolism with NAD-ME decarboxylation, despite lacking Kranz anatomy. The C4-activity was still present at high CO2 suggesting that it could be constitutive. O. alismoides at low CO2 showed diel acidity variation of up to 34 μequiv g-1 FW indicating it may also operate a form of Crassulacean Acid Metabolism (CAM). pH-drift experiments showed that both species were able to use bicarbonate. In O. acuminata, the kinetics of carbon uptake were altered by CO2 growth conditions, unlike in O. alismoides. Thus the two species appear to regulate their carbon concentrating mechanisms differently in response to changing CO2. The Hydrocharitaceae have many species with evidence for C4, CAM, or a metabolism involving organic acids, and are worthy of further study.

Item Type: Publication - Article
Digital Object Identifier (DOI): https://doi.org/10.1007/s11120-013-9950-y
CEH Sections/Science Areas: Parr
ISSN: 0166-8595
Additional Keywords: bicarbonate use, CAM, C4 metabolism, organic acids, photosynthesis
NORA Subject Terms: Botany
Date made live: 07 Jul 2014 14:03 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/507685

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