C2 photosynthesis generates about 3-fold elevated leaf CO2 levels in the C3-C4 intermediate species Flaveria pubescens.

Formation of a photorespiration-based CO2-concentrating mechanism in C3-C4 intermediate plants is seen as a prerequisite for the evolution of C4 photosynthesis, but it is not known how efficient this mechanism is. Here, using in vivo Rubisco carboxylation-to-oxygenation ratios as a proxy to assess relative intraplastidial CO2 levels is suggested. Such ratios were determined for the C3-C4 intermediate species Flaveria pubescens compared with the closely related C3 plant F.

Tree age-dependent changes in photosynthetic and respiratory CO2 exchange in leaves of micropropagated diploid, triploid and hybrid aspen.

The growth rate of triploid European aspen (Populus tremula L.) and hybrid aspen (P. tremula × Populus tremuloides Michx.

Temperature responses of dark respiration in relation to leaf sugar concentration.

Changes in leaf sugar concentrations are a possible mechanism of short-term adaptation to temperature changes, with natural fluctuations in sugar concentrations in the field expected to modify the heat sensitivity of respiration. We studied temperature-response curves of leaf dark respiration in the temperate tree Populus tremula (L.) in relation to leaf sugar concentration (1) under natural conditions or (2) leaves with artificially enhanced sugar concentration.

Quantitative analysis of photosynthetic carbon metabolism in protoplasts and intact leaves of barley. Determination of carbon fluxes and pool sizes of metabolites in different cellular compartments.

Rates of carbon fluxes and pool sizes of photosynthetic metabolites in different cellular compartments of barley protoplasts were calculated from the time curves of their labeling in the medium of ¹⁴CO₂. Using membrane filtration procedure, kinetics of ¹⁴C incorporation into the products of steady-state photosynthesis was determined separately in chloroplasts, mitochondria and cytosol of barley protoplasts illuminated for different periods in the air containing ¹⁴CO₂. To extract the quantitative information, analytical labeling functions P(t) describing the dependence of ¹⁴C content in the primary, intermediate and end products of a linear reaction chain upon the duration of tracer feeding have been derived.

Influence of mitochondrial genome rearrangement on cucumber leaf carbon and nitrogen metabolism.

The MSC16 cucumber (Cucumis sativus L.) mitochondrial mutant was used to study the effect of mitochondrial dysfunction and disturbed subcellular redox state on leaf day/night carbon and nitrogen metabolism. We have shown that the mitochondrial dysfunction in MSC16 plants had no effect on photosynthetic CO(2) assimilation, but the concentration of soluble carbohydrates and starch was higher in leaves of MSC16 plants.

Light- and CO2-saturated photosynthesis: enhancement by oxygen.

Oxygen may enhance CO2-saturated photosynthesis in intact leaves, which display the Warburg effect when illuminated at the current atmospheric level of CO2 and O2, of about 350 microl l(-1) and 21%, respectively. The magnitude of the stimulation depends on irradiance. The K(M)(O2) of the stimulation is 128 microM (10.