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Gas exchanges of wheat (Triticum aestivum L. cv. Courtot) shoots were measured before and during a water stress. While photosynthesis, transpiration and dark respiration decreased because of the stress, photorespiration increased initially, up to a maximum of 50% above its initial value. The CO2 concentration in the intercellular space was calculated from(More)
Wheat was cultivated in a small phytotronic chamber. (18)O(2) was used to measure the O(2) uptake by the plant, which was recorded simultaneously with the O(2) evolution, net CO(2) uptake, and transpiration. At normal atmospheric CO(2) concentration, photorespiration, measured as O(2) uptake, was as important as the net photosynthesis. The level of true(More)
The 24 h O2 uptake and release together with the CO2 balance have been measured in two CAM plants, one a non-succulent Sempervivum grandifolium, the other a succulent Prenia sladeniana. The O2 uptake was estimated by the use of (18)O2. It was found that the mean hourly O2 uptake in the light was 7 times that in the dark for Sempervivum and 5 times that for(More)
The rate of HCO(3) (-) uptake by the red macroalga Chondrus crispus has been investigated. Unbalanced concentrations of free CO(2) and HCO(3) (-), generated by the photosynthetic activity, were detected in steady state conditions by using an exchange column apparatus linked to an assimilation chamber. Observing the variations of this gradient as influenced(More)
All measurements of photorespiration and gross photosynthesis in leaves, whether using isotopes or not, are underestimated because of the recycling of O(2) or CO(2). On the basis of a simple diffusion model, we propose a method for the calculation of the recycling and the corresponding underestimation of the measurements. This procedure can be applied when(More)
Unidirectional O(2) fluxes were measured with (18)O(2) in a whole plant of wheat cultivated in a controlled environment. At 2 or 21% O(2), O(2) uptake was maximum at 60 microliters per liter CO(2). At lower CO(2) concentrations, it was strongly inhibited, as was photosynthetic O(2) evolution. At 2% O(2), there remained a substantial O(2) uptake, even at(More)
A tabu random walk on a graph is a partially self-avoiding random walk which uses a bounded memory to avoid cycles. This memory is called a tabu list and contains vertices already visited by the walker. The size of the tabu list being bounded, the way vertices are inserted and removed from the list, called here an update rule, has an important impact on the(More)
A tabu random walk on a graph is a partially self-avoiding random walk to nearest neighbors with finite memory. The walker is endowed with a finite word, called tabu list, whose letters are vertices he has already visited. The policy to insert or remove occurrences of vertices in the tabu list is called update rule. First, we enunciate a necessary and(More)
The cultivation of wheat (Triticum aestivum L.) was performed in controlled environment chambers with the continuous monitoring of photosynthesis, dark respiration, transpiration and main nutrient uptakes. A protocol in twin chambers was developed to compare the specific effects of low O2 and high CO2. Each parameter is able to influence photosynthesis but(More)