Carbon allocation strategies and water uptake in young grafted and own-rooted hazelnut (CorylusavellanaL.) cultivars

In this study, grafted and own-rooted young hazelnut plants of three high-quality cultivars were cultivated in Central Italy to investigate possible differences in growth, fruit and flower production, and physiological processes encompassing water uptake, photosynthetic variables, and non-structural carbohydrates (NSC) allocation. Stable isotopes and photosynthetic measurements were used to study carbon and water fluxes in plants. For the first time an ecophysiological study was carried out to understand the seasonal growth dynamics of grafted plants in comparison with own-rooted plants. The own-rooted hazelnuts showed rapid aboveground development with large canopy volume, high amount of sprouts and earlier yield. The grafted plants showed greater belowground development with lower canopy volumes and lower yield. However, later, the higher growth rates of the canopy led these plants to achieve the same size as that of the own-rooted hazelnuts and to enter the fruit production phase. Different seasonal behaviour in root water uptake and leaf photosynthetic-related variables were detected between the two types of plants. The grafted plants showed root development that allowed deeper water uptake than that of the own-rooted hazelnuts. Moreover, the grafted plants were characterized by a higher accumulation of carbohydrate reserves in their root tissues and by higher stomatal reactivity, determining a major plasticity in response to seasonal thermal variations.