Contribution of different levels of plant canopy to total carbon assimilation and intrinsic water use efficiency of Manto Negro and Tempranillo grapevines

The contribution of different canopy levels to total dry matter production along the berry growing season (July-August) and their water use efficiency were measured in a Mallorcan vineyard on two grapevine cultivars: Tempranillo, a common one in Spain, and Manto Negro, a local cultivar of Mallorca. The training system was the typical "goblet" for Manto Negro and a bilateral cordon for Tempranillo. The vineyards were cultivated without irrigation, as is traditional in this area. The daily carbon assimilation was estimated from diurnal time courses of leaf photosynthesis in eight different canopy positions at three different dates from mid July to mid August. The upper canopy layer (level 4) was the more active one.: From July to August photosynthesis dropped from 350 to 150 mmol m(-2) day(-1) for Manto Negro and from 525 to 60 mmol m(-2) day(-1) for Tempranillo. Apart from level 4, the highest values were found in southeast and northwest-facing leaves of the upper levels (3 and 5), and the lowest in the inner part of the canopy (level 8). Intrinsic water use efficiency increased along the growing season for all levels. The highest values corresponded to the highest daily carbon assimilation. At the end of the growing season (early September), the total leaf area and dry mass and fruit weight were measured. Level 8 had 29% of the total plant leaf dry matter in Tempranillo, and 39% in Manto Negro. The remanding levels fluctuated between 5 and 20%. Estimates of the contribution of each level to fruit growth plant production were obtained showing good agreement with plant berry weight at harvest.