Journal
JOURNAL OF EXPERIMENTAL BOTANY
Volume 62, Issue 9, Pages 3183-3195Publisher
OXFORD UNIV PRESS
DOI: 10.1093/jxb/err059
Keywords
C-3-C-4 intermediate; C-4 photosynthesis; gas exchange; Kranz anatomy; photorespiration; photosynthetic
Categories
Funding
- Natural Science and Engineering Research Council of Canada (NSERC)
- International Rice Research Institute
Ask authors/readers for more resources
This study investigated whether Euphorbia subgenus Chamaesyce subsection Acutae contains C-3-C-4 intermediate species utilizing C-2 photosynthesis, the process where photorespired CO2 is concentrated into bundle sheath cells. Euphorbia species in subgenus Chamaesyce are generally C-4, but three species in subsection Acutae (E. acuta, E. angusta, and E. johnstonii) have C-3 isotopic ratios. Phylogenetically, subsection Acutae branches between basal C-3 clades within Euphorbia and the C-4 clade in subgenus Chamaesyce. Euphorbia angusta is C-3, as indicated by a photosynthetic CO2 compensation point (G) of 69 mu mol mol(-1) at 30 degrees C, a lack of Kranz anatomy, and the occurrence of glycine decarboxylase in mesophyll tissues. Euphorbia acuta utilizes C-2 photosynthesis, as indicated by a G of 33 mu mol mol(-1) at 30 degrees C, Kranz-like anatomy with mitochondria restricted to the centripetal (inner) wall of the bundle sheath cells, and localization of glycine decarboxlyase to bundle sheath mitochondria. Low activities of PEP carboxylase, NADP malic enzyme, and NAD malic enzyme demonstrated no C-4 cycle activity occurs in E. acuta thereby classifying it as a Type I C-3-C-4 intermediate. Kranz-like anatomy in E. johnstonii indicates it also utilizes C-2 photosynthesis. Given the phylogenetically intermediate position of E. acuta and E. johnstonii, these results support the hypothesis that C-2 photosynthesis is an evolutionary intermediate condition between C-3 and C-4 photosynthesis.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available