Accumulation and localization of phenolic compounds under future
environmental conditions: the joint effects of CO2
concentration and light intensity
Abstract
Barley (Hordeum vulgare) accumulates phenolic compounds (PhCs), which
play a key role in tolerance to environmental stress. The influence of
irradiance and atmospheric CO2 concentration
([CO2]) on the accumulation and localization of PhCs
in barley leaves was examined for two varieties with different
tolerances to oxidative stress. PhC localization was visualized using
Naturstoff reagent A and fluorescence microscopy. Close relationships
were found between fluorescence-determined localization of PhCs in
barley leaves and PhC content estimated using liquid chromatography
coupled with mass spectroscopy detection. High intensity light had the
strongest effect on the accumulation of PhCs, but total PhC content
converged at elevated [CO2], minimizing the
differences between high and low irradiance. PhCs localized
preferentially near the surfaces of leaves, but under low light,
increasing allocation of PhCs deeper mesophyll layers was observed. The
PhC profile was very different between barley varieties. Our research
presents novel evidence that [CO2] modulates the
accumulation of PhCs accumulation in barley leaves. Mesophyll cells,
rather than epidermal cells, were most responsive to environmental
stimuli in terms of PhC accumulation. The relatively tolerant variety
accumulated significantly more hydroxycinnamic acids, indicating these
PhCs may play a more prominent role in oxidative stress prevention.