WHOLE CANOPY GAS EXCHANGES AND LIGHT INTERCEPTION OF THREE PEACH TRAINING SYSTEMS

Canopy photosynthesis (A(c)), transpiration (E-c) 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 A, started to decrease in the afternoon, even if light was not a limiting factor. Both canopies reached similar maximum E-c rates in late afternoon. On the contrary, A(c) 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.