Role of D-genome chromosomes in photosynthesis expression in wheats.

The role of D-genome chromosomes in the expression of net photosynthesis in wheats was analysed with the nullitetrasomic and ditelosomic lines of the bread wheat cultivar 'Chinese Spring'. The two arms of chromosome 3 D and the short arm of chromosome 6 D control major mechanisms of photosynthesis. The effect of chromosome 6 D can be thoroughly compensated by that of its homoeologues of genomes A or B, contrary to what can be observed for chromosome 3 D. Chromosome 7 D is responsible for the low photosynthesis of flag leaves developed under high irradiances in genotypes possessing the D-genome, as the likely result of ontogeny or of a loss in adaptability to irradiance.