Progress has been made in the understanding of photorespiration and related proteins (Rubisco, glycolate oxidase and glycine decarboxylase) in the context of recent structural information. Numerous shuttles exist to support transamination, ammonia refixation and the supply or export of reductants generated or consumed (via malate-oxaloacetate shuttles) in the photorespiratory pathway. A porin-l...

BACKGROUND AND AIMS Rice (Oryza sativa) plants lose significant amounts of volatile NH(3) from their leaves, but it has not been shown that this is a consequence of photorespiration. Involvement of photorespiration in NH(3) emission and the role of glutamine synthetase (GS) on NH(3) recycling were investigated using two rice cultivars with different GS activities. METHODS NH(3) emission (AER)...

We investigated the effects of P(SARK)IPT (for Senescence-Associated Receptor KinaseIsopentenyltransferase) expression and cytokinin production on several aspects of photosynthesis in transgenic tobacco (Nicotiana tabacum cv SR1) plants grown under optimal or restricted (30% of optimal) watering regimes. There were no significant differences in stomatal conductance between leaves from wild-type...

In a study on metabolic consumption of photosynthetic electrons and dissipation of excess light energy under water stress, O2 and CO2 gas exchange was measured by mass spectrometry in tomato plants using 18O2 and 13CO2. Under water stress, gross O2 evolution (E(O)), gross O2 uptake (U(O)), net CO2 uptake (PN), gross CO2 uptake (TPS), and gross CO2 evolution (Ec) declined. The ratio P(N)/E(O) fe...

Photosynthetic bacteria, such as Rhodopseudomonas capsulata, when incubated in the light under conditions of nitrogen starvation, produce copious amounts of hydrogen gas via nitrogenase, presumably as a means of regulating their energy charge and/or redox balance and thereby preventing photooxidative damage until growth can begin again [1,2]. A similar role has been suggested for the hydrogenas...

The hypothesis that net photosynthesis is diminished in many plant species because of a high rate of CO(2) evolution in the light has been tested further. High rates of CO(2) output in CO(2)-free air in comparison with dark respiration were found in Chlamydomonas reinhardi, wheat leaves, tomato leaves, and to a lesser extent in Chlorella pyrenoidosa by means of the (14)C-photorespiration assay....

Terrestrial vegetation currently absorbs approximately a third of anthropogenic CO2 emissions, mitigating the rise of atmospheric CO2. However, terrestrial net primary production is highly sensitive to atmospheric CO2 levels and associated climatic changes. In C3 plants, which dominate terrestrial vegetation, net photosynthesis depends on the ratio between photorespiration and gross photosynthe...

Ferredoxin-dependent glutamate synthase (Fd-GOGAT) plays a major role in photorespiration in Arabidopsis, as has been determined by the characterization of mutants deficient in Fd-GOGAT enzyme activity (gls). Despite genetic evidence for a single Fd-GOGAT locus and gene, we discovered that Arabidopsis contains two expressed genes for Fd-GOGAT (GLU1 and GLU2). Physical and genetic mapping of the...