The effect of leaf area reduction in Merlot grapevines was tested in well irrigated vines and in vines under water deficit. The effect was monitored over two consecutive seasons. In full irrigation regime (I) vines were irrigated weekly to maintain midday stem water potential (Ψstem) between −0.3 and −0.6 MPa. In water deficit (D) condition, irrigation was managed in order to maintain Ψstem between −1.0 and −1.4 MPa from fruit set to harvest. Within each irrigation regime two different levels of canopy height were imposed: high canopy (110 cm) and short canopy (60 cm). Canopy reduction under full irrigation and water deficit conditions produced different results. Brix degrees were reduced only under well irrigated conditions, while under water deficit no effects of canopy reduction were observed. The reduction of leaf area did not influence the anthocyanin and tannin concentrations.
