Microclima termico e luminoso e accumulo di antociani in ‘Nebbiolo’

The thermal and light microclimate of Nebbiolo bunches has been modified for the period of grape ripening. One week before the supposed veraison timing some bunches have been closed inside boxes made according the standard format of a meteorological screen box. During maturation berry temperature has been monitored in different light availability conditions (fully exposed, below a leaf layer, inside the box). Thermal course data have been processed according to normalized thermal units in relation to the physiological effectiveness in terms of anthocyanin synthesis. Exposed bunches in respect to shaded ones, by leaves or boxes, accumulated a significant lower number of thermal units due to the daytime excessive temperature, particularly frequent in the first part of the maturation period. Nevertheless exposed bunches showed an earlier and intensive anthocyanin accumulation of shaded ones. However shaded bunches were able to reach the same final level in anthocyanins thanks to the more persistent rate of accumulation in the last part of ripening. The higher light availability was also able to modify the athocyanin profiling reducing the relative amount of methilated anthocyanidins (malvidin in particular) in favor of no-methilated ones (cyanidin and delphinidin).