HEADSPACE GAS-COMPOSITION IN 4 PRUNUS-AVIUM CULTIVARS WITH DIFFERING PHOTOSYNTHETIC CAPABILITIES

Endogenous and exogenous volatile substances were analyzed during 30 days' incubation of four cultivars of the Prunus avium species grown in vitro on a proliferation medium. Cultivars Bigarreau Moreau and Bigarreau Burlat show photosynthetic capability at 35 mumol . m-2 . s-1; oxygen concentration slightly increased (22 to 24%), carbon dioxide was lowered to less than 300 mu . liter-1, and low ethylene (0.8 to 1.2 . liter-1) accumulation was recorded. Quite different headspace evolution was observed during growth of cultivars Victoria and Casavecchia: a large oxygen concentration decrease was accompanied by a sharp carbon dioxide increase (19%) and ethylene boost (4 to 5 mul . liter-1). The evolution of these gaseous metabolites has been correlated to photosynthetic incapability and respiratory stress responsible for leaf yellowing and tissue softening observed when acetaldehyde and ethanol started to form in cultivars Victoria and Casavecchia. Dry and fresh weight were measured, and no substantial difference was recorded among cultures with low and high photosynthetic capability. Evidence is reported that different genotypes within the same species may follow different metabolic pathways.