Contribution of hydroxycinnamates and flavonoids to epidermal shielding of UV‐A and UV‐B radiation in developing rye primary leaves as assessed by ultraviolet‐induced chlorophyll fluorescence measurements

摘要: Epidermally located ultraviolet (UV)-absorbing phenolic compounds, flavonoids and hydroxycinnamic acid esters (HCAs), can shield the underlying tissues in plants against harmful UV-radiation. The relative importance of two different classes compounds for UV-screening was a matter recent debate. Using non-invasive method based on chlorophyll fluorescence measurements to estimate epidermal UV transmittance, relationship between shielding content groups secondary layers photosynthetic mesophyll developing rye primary leaves grown under supplementary UV-B radiation investigated. From fourth tenth day after sowing, epidermally increased an age- irradiation-dependent manner, whereas HCAs, mainly ferulic p-coumaric esters, were constitutively present did not vary their contents over observed time period. There excellent correlation UV-A absorbances as assessed by flavonoids. However, HCAs showed additional contribution shielding. In contrast, seem play respective role. When abaxial adaxial compared, it became apparent that fully expanded from both sides equally effective absorption earlier more UV-exposed epidermis young unrolling significantly higher absorption. It is shown early stages development are dominant protective leaf. This function increasingly replaced during leaf acclimation. application has been proven be useful tool estimating these tissue.