EFFECT OF IRRIGATION ON PHYSIOLOGICAL AND BIOCHEMICAL TRAITS OF HAZELNUTS (CORYLUS AVELLANA L.)

Leaf gas-exchange parameters (A, g_s, C_i and A/g_s), leaf water potential (Ψ_leaf), and leaf metabolites (photosynthetic pigments, soluble sugars and starch) were measured in ‘Grada de Viseu’ (a traditional portuguese hazelnut cultivar) under four different irrigation treatments based on ET_c levels (100, 75, 50 and 0%), in 2003. There were significant differences between the four irrigation treatments with respect to chlorophyll a (Chl_a), chlorophyll b (Chl_b), total chlorophyll (Chl_total) and carotenoids (P < 0.001), in g_s, C_i and soluble sugars (P < 0.01), and also with respect to starch and total sugar content (P < 0.05). At ET_c 100 and ET_c 75, ‘Grada de Viseu’ showed the highest levels of A, g_s, and C_i. Levels of metabolites (Chl_a, Chl_b, Chl_total and carotenoids) were also consistently higher in these treatments than in others. Our evaluation indicates that irrigation conditions during hazelnut growth have a great influence on physiological parameters and probably also on fruit quality. However, data for several more years and/or different irrigation treatments are required before any firm conclusions can be drawn on these issues.