Relationships among meteorological data, leaf gas exchange and anthocyanin content in ‘Nebbiolo’ berries grown in three different vineyards.

This study was carried out in three vineyards (Alba, Serralunga and Novello, Cuneo Province, Italy) characterized by different soil and climate conditions. A meteorological station was located in each vineyard to measure temperature, relative humidity and rainfall. Vines were trained to the vertical trellis systems, and the vine canopy was ideally horizontally divided into three zones, each about 35 cm high, where ecophysiological parameters (leaf gas exchange, shoot water potential and leaf area of the canopy) were measured twice a week during summer 2010. In July, a reduction of carbon assimilation was measured; transpiration was on the contrary not reduced, suggesting an increase in photorespiration in accordance with maximum temperatures measured in the same period. Stomatal conductance indicated that during the season no severe water stress was detected in the three vineyards. The relations detected in the three vineyards between water potential and transpiration lead to the conclusion that ‘Nebbiolo’ shows an anisohydric response to water stress. In all the three vineyards studied, the highest zone of the canopy was characterized by high levels of photosynthesis and transpiration. A reduction of vine ecophysiological performances was detected at the end of the season in the vineyards of Serralunga and Novello but not in the Alba vineyard. At harvest the anthocyanin content was measured by means of an optical portable sensor, Multiplex® (ForceA, Paris, France) whose mechanism of measurement is based on the chlorophyll fluorescence method. The total anthocyanin content was similar in the grapes from Novello and Alba whereas lower contents were detected in grapes from Serralunga. The relations among temperature regimes, ecophysiological performances before and after ripening, and anthocyanin contents at harvest are discussed.