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- Title
Biochemical and biophysical CO concentrating mechanisms in two species of freshwater macrophyte within the genus Ottelia (Hydrocharitaceae).
- Authors
Zhang, Yizhi; Yin, Liyan; Jiang, Hong-Sheng; Li, Wei; Gontero, Brigitte; Maberly, Stephen
- Abstract
Two freshwater macrophytes, Ottelia alismoides and O. acuminata, were grown at low (mean 5 μmol L) and high (mean 400 μmol L) CO concentrations under natural conditions. The ratio of PEPC to RuBisCO activity 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 CO, respectively, as a result of a twofold increase in PEPC activity. The activity of PPDK was similar to, and changed 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 C metabolism with NAD-ME decarboxylation, despite lacking Kranz anatomy. The C-activity was still present at high CO suggesting that it could be constitutive. O. alismoides at low CO showed diel acidity variation of up to 34 μequiv g FW indicating that 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 CO growth conditions, unlike in O. alismoides. Thus, the two species appear to regulate their carbon concentrating mechanisms differently in response to changing CO. O. alismoides is potentially using three different concentrating mechanisms. The Hydrocharitaceae have many species with evidence for C, CAM or some other metabolism involving organic acids, and are worthy of further study.
- Subjects
PHYSIOLOGICAL effects of carbon monoxide; BIOCHEMISTRY; HYDROCHARITACEAE; MACROPHYTES; ALGAL growth; DECARBOXYLATION
- Publication
Photosynthesis Research, 2014, Vol 121, Issue 2/3, p285
- ISSN
0166-8595
- Publication type
Article
- DOI
10.1007/s11120-013-9950-y