Résumé
Tetraploid (4x) citrus resulting from chromosome doubling present a morphology and an anatomy quite different than their respective diploid (2x). Recent investigations suggest that this plant material is promising regarding its adaptation to abiotic constraints. Gas exchanges (ambient [CO2] and doubled [CO2]) in different couples of 2x and doubled diploids were investigated: Poncirus, Cleopatra mandarin and Cleopatra mandarin x Poncirus intergeneric hybrid. Stomata size and density were measured in young and mature leaves. Candidate genes involved stomata size and density were also studied. Tetraploid presented most of the time lower gas exchanges then the respective 2x. At doubled CO2 concentration, water use efficiency of 4x was however much higher than in 2x, an opposite trend being observed regarding the stomata density, whatever the developmental status of the leaf. Gene expression was similar in 2x and 4x for Poncirus and Cleopatra mandarin while it was much higher in the 4x intergenetic hybrid compared to its 2x. Physiology and genes expression is discussed in relation to the genetic status of the genotypes. (Texte intégral)