Whole canopy gas exchanges and light interception of three peach training systems

Canopy photosynthesis (Acv), transpiration (Ec) and light interception of three peach training systems, delayed vasette (DV), palmette (P), and Y-trellis (Y), were measured by a whole-canopy gas exchange open system, and a custom-built all-wave scanner-recorder. Whole-canopy assimilation rates peaked before midday in both DV and P, then Ac started to decrease in the afternoon, even if light was not a limiting factor. Both canopies reached similar maximum Ec rates in late afternoon. On the contrary, Ac of the east and west sides of the Y was nearly constant between 10:00 and 15:00 hours. In DV and P, the assimilation-transpiration ratio (ATR) decreased from early morning hours to a minimum in early afternoon, increasing thereafter. In the Y, ATR values were higher than in DV and P and, after the initial morning decrease, they remained stable until the end of the day. On a hectare base, light interception in DV and P was similar, while Y showed higher interception throughout the day. Whole-canopy photosynthesis was linearly related to the amount of light intercepted by the tree.