Physiological responses and fruit composition of two red grape varieties under different light regimes

To evaluate grapevine physiological responses to light regimes, two Sardinian
red varieties were covered with two different screening plastic films (Visible (VIS)
and UV-A+VIS), compared to a control sunlight exposed. From veraison until
harvest light intensity and spectral quality were monitored. Canopy, berry skin and
flesh temperature were continuously acquired with thermocouples inserted into
berries. Plant physiological status, berry anthocyanin and total polyphenols content
were correlated with the cluster thermal regimes and light exposure. No significant
differences were found among the films, in canopy and clusters microclimate, and in
fruit final composition. The imposed light regimes affected microclimate conditions,
total polyphenols and anthocyanin contents but did not induce significant
differences on plants physiological status and berry main flesh components. The
observed microclimate differences between varieties were related to plant structure
and cluster exposure.