Résumé
Soldanella alpina differing in leaf epidermal UV-A absorbance (DEA(375)), as measured with the Dualex, was investigated as a model alpine plant for the flavonoid (Flay) composition and concentration and for anatomical and pigment characteristics. In sun leaves, twenty-three flavones were characterised by their mass formula, their maximum absorption, their glycosylation, their methylation and dehydroxylation pattern. The flavones belonged to four subfamilies (tetra-hydroxy-flavones, penta-hydroxy-flavones, penta-hydroxy-methyl-flavones and trihydroxy-di-methoxy-flavones), abundant in sun and shade leaves. Their concentration was estimated by their absorption at 350 nm after HPLC separation. Sun leaves contained relatively higher contents of penta-hydroxymethyl-flavones and shade leaves higher contents of tetra-hydroxy-flavones. The flavones were present mainly in vacuoles, all over the leaf. After shade-sun transfer, the content of most flavones increased, irrespective of the presence or absence of UV radiation. Highly significant correlations with the log-transformed DEA(375) suggest that DEA(375) can be readily applied to predict the flavone content of S. alpina leaves. Shade-sun transfer of leaves decreased the hydroxycinnamic acid (HCA) content, the mass-based chlorophyll (Chl) a + b content and the Chl/Carotenoid (Car) ratio but increased DEA(375), and the Car content. Together with previously reported anatomical characteristics all these parameters correlated significantly with the DEA(375). The Flay content is therefore correlated to most of the structural characteristics of leaf acclimation to light and this can be probed in situ by DEA(375).