C/sub 4/ photosynthesis in Euphorbia degeneri and E. remyi: a comparison of photosynthetic carbon metabolism in leaves, callus cultures and regenerated plants

Technical Report · Sun Apr 01 00:00:00 EST 1984

DOI:https://doi.org/10.2172/6783854· OSTI ID:6783854

Ruzin, S E

Based on analysis of /sup 14/CO/sub 2/ fixation kinetics and assays of enzymes related to C/sub 4/ metabolism (NAD-ME, NADP-ME, NAD-MDH, NADP-MDH, AST, ALT), leaves and regenerated plants of Euphorbia degeneri exhibit a modified NADP-ME-type photosynthesis. Apparently, both aspartate and malate are used for transport of CO/sub 2/ to bundle sheath cells. Callus grown on either non-shoot-forming or shoot-forming media fixes CO/sub 2/ into RPP-cycle intermediates and sucrose, as well as malate and aspartate. /sup 14/CO/sub 2/ pulse/chase kinetics show no significant loss of label from C/sub 4/ acids throughout a one minute chase. Analysis of PEPCase revealed the presence of 2 isoenzymes in both leaf and regenerated plant tissues (K/sub m/ (PEP) = 0.080 and 0.550) but only one isoenzyme in callus (K/sub m/ = 0.100). It appears that C/sub 4/ photosynthesis does not occur in callus derived from this C/sub 4/ dicot but is regenerated concomitant with shoot regeneration, and ..beta..-carboxylation of PEP in callus, mediated by the low K/sub m/ isoenzyme of PEPCase, produces C/sub 4/ acids that are not involved in the CO/sub 2/ shuttle mechanism characteristic of C/sub 4/ photosynthesis. 161 references, 19 figures, 12 tables.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6783854
• Report Number(s): LBL-17768; ON: DE84013238
• Resource Relation: Other Information: Thesis
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CARBON DIOXIDE
METABOLITES
PHOTOSYNTHESIS
BIOCHEMICAL REACTION KINETICS
ENZYME ACTIVITY
ASPARTIC ACID
CARBON 14 COMPOUNDS
CHLOROPHYLL
EXPERIMENTAL DATA
MALEIC ACID
MICROSCOPY
PLANTS
PYRUVIC ACID
TISSUE CULTURES
TRACER TECHNIQUES
AMINO ACIDS
CARBON COMPOUNDS
CARBON OXIDES
CARBOXYLIC ACIDS
CHALCOGENIDES
CHEMICAL REACTIONS
DATA
DICARBOXYLIC ACIDS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
INFORMATION
ISOTOPE APPLICATIONS
KETO ACIDS
KINETICS
LABELLED COMPOUNDS
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHYTOCHROMES
PIGMENTS
PORPHYRINS
REACTION KINETICS
SYNTHESIS
550201* - Biochemistry- Tracer Techniques