The effects of 2 nitrate levels, 14 (CK) and 140 mmol L (T), on the leaf gas exchange variables of cucumber (Cucumis sativus L. cv. Xintaimici) seedlings grown in hydroponic culture were investigated. Photosynthetic lightand CO2-response curves from CK and T seedlings were determined and used for the analysis of photosynthetic capacity. The results showed that nitrate stress resulted in a signi...

Carbon dioxide (CO2 ) represents the most abundant and accessible carbon source on Earth. Thus the ability to transform CO2 into valuable commodity chemicals through the construction of C-C bonds is an invaluable strategy. Carboxylic acids and derivatives, the main products obtained by carboxylation of carbon nucleophiles by reaction of CO2 , have wide application in pharmaceuticals and advance...

The pentapeptide Phe-Leu-Glu-Glu-Leu, tritiated at the gamma carbon of each Glu residue, has been synthesized. In a system using microsomal preparations derived from rat liver, vitamin K-dependent tritium release from the L-Glu residues of this substrate can occur without the concurrent gamma-carboxylation of Glu. This tritium release reaction, which indicates cleavage of the gamma C-H bond, al...

Fertilization commonly increases biomass production in loblolly pine ( Pinus taeda L.). However, the sequence of short-term physiological adjustments allowing for the establishment of leaf area and enhanced growth is not well understood. The effects of fertilization on photosynthetic parameters, root respiration, and growth for over 200 d following the application of diammonium phosphate were i...

The retinal pigment epithelium (RPE) is a monolayer of pigmented cells that requires an active metabolism to maintain outer retinal homeostasis and compensate for oxidative stress. Using 13C metabolic flux analysis in human RPE cells, we found that RPE has an exceptionally high capacity for reductive carboxylation, a metabolic pathway that has recently garnered significant interest because of i...

Vertebrates possess 2 proteins with vitamin K oxidoreductase (VKOR) activity: VKORC1, whose vitamin K reduction supports vitamin K-dependent (VKD) protein carboxylation, and VKORC1-like 1 (VKORC1L1), whose function is unknown. VKD proteins include liver-derived coagulation factors, and hemorrhaging and lethality were previously observed in mice lacking either VKORC1 or the γ-glutamyl carboxylas...

Gas exchange of Eurasian watermilfoil (Myriophyllum spicatum L.) indicated a near-zero CO(2) compensation point and a high temperature optimum for photosynthesis. These properties are characteristic of plants fixing CO(2) by a beta-carboxylation mechanism. Operation of the Calvin cycle was shown and no evidence for beta-carboxylation was obtained. These results indicate that near-zero CO(2) com...

Photosynthetic data collected from Pisum sativum L. and Phaseolus vulgaris L. plants at different stages of development were related to symbiotic N(2) fixation in the root nodules. The net carbon exchange rate of each leaf varied directly with carboxylation efficiency and inversely with the CO(2) compensation point. Net carbon exchange of the lowest leaves reputed to supply fixed carbon to root...