How do grapevine leaf phenolic contents respond to daily changes in environmental factors?

Csepregi, Kristóf and Kőrösi, László and Teszlák, Péter and Hideg, Éva (2018) How do grapevine leaf phenolic contents respond to daily changes in environmental factors? In: International Association of Plant UV Research 2nd Network Meeting, 2018.04.15-18., Bled (Slovenia).

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Abstract

Grapevine leaves are rich in phenolic compounds, many of which are – among fulfilling other roles – efficient antioxidants (Csepregi et al. 2016, Csepregi and Hideg 2017). The long-term aim of a recently launched project is to explore the functional plasticity of phenolic compounds in grapevine leaves. Here we present results of a pilot study, registering and analysing hour-by-hour changes in photosynthesis, phenolic profiles and antioxidant capacities of South-facing Pinot noir leaves between 7 am and 7 pm during a clear summer day mid-July at Pécs (N46.071, E18.156). During this 12h period, photosynthetically active radiation (PAR) was 80-2130 µmol/m2/s and UV radiation (UV-A+B) varied between 5-46.1 kJ/m2 as physical dose measured on site. Local data were separated into UV-B (280-315 nm) and UV-A (315-400 nm) regions based on a model calculation (NCAR). Total adaxial flavonoid content (measured as Dualex flavonoid index) varied between 88% and 112% of the daily average and showed strong positive correlations with PAR, UV-A, UV-B, leaf temperature and net CO2 assimilation. Stomatal conductance (gs) was positively correlated with PAR, UV-A and UV-B. However, substomatal CO2 concentrations (Ci) were only correlated with PAR (positively) and not with UV. Hourly changes in leaf antioxidant capacities and phenolic profiles measured with HPLC-DAD complete the analysis.

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