Abstract
Barley (Hordeum vulgare) accumulates phenolic compounds (PhCs), which play a key role in plant defense against environmental stressors as antioxidants or UV screening compounds. The influence of light 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 in vivo using 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. Light intensity had the strongest effect on the accumulation of PhCs, but the total PhC content was similar at elevated [CO2], minimizing the differences between high and low light. PhCs localized preferentially near the surfaces of leaves, but under low light, an increasing allocation of PhCs in deeper mesophyll layers was observed. The PhC profile was significantly different between barley varieties. The relatively tolerant variety accumulated significantly more hydroxycinnamic acids, indicating that these PhCs may play a more prominent role in oxidative stress prevention. Our research presents novel evidence that [CO2] modulates the accumulation of PhCs in barley leaves. Mesophyll cells, rather than epidermal cells, were most responsive to environmental stimuli in terms of PhC accumulation.
Highlights
After treatment with Naturstoff reagent A, three colors of fluorescence were observed when leaves were excited by UV radiation: Red from chlorophyll, blue from autofluorescent phenolic compounds (PhCs), and yellow from flavonoids reacting with the reagent
The presence of lignin was confirmed in the vascular bundles via phloroglucinol HCl histochemical detection, it was not detected in the epidermis or sclerenchyma cells (Figure 2b)
We are aware that due to heterogeneity in excitation wavelength penetration into the leaf tissues [45] our proposed approach cannot replace quantification of PhCs, such as fluorescence spectroscopy or highperformance liquid chromatography (HPLC)-high-resolution mass spectrometer (HRMS), which were used in the present study
Summary
The influence of light 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. 1. Introduction with regard to jurisdictional claims in Barley (Hordeum vulgare) is one of the most widely cultivated and economically important crops. Introduction with regard to jurisdictional claims in Barley (Hordeum vulgare) is one of the most widely cultivated and economically important crops It is considered a founder crop in agriculture, with archaeological evidence placing its domestication back 10,000 years ago [1]. Europe can expect greater variability between harvests [7] Despite these projections, barley maintains a reputation for being resilient to environmental stress and is expected to be less impacted than other crops, such as corn or potatoes [7]
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