UV-excited chlorophyll fluorescence as a tool for the assessment of UV-protection by the epidermis of plants

Recently, a new method for estimating epidermal transmission of UV radiatio n in higher plants as been proposed. The empirical evidence for the usefuln ess of this method is reviewed here. Direct comparison with spectroscopical ly determined epidermal transmission yielded equivalent results. A linear c orrelation to the concentration of epidermal screening compounds has been s hown. Relating UV-A and UV-B absorbance allowed some preliminary conclusion s about the chemical nature of the screening compounds. A new portable appa ratus is presented for the first time, which allows the non-destructive ass essment of UV-A screening even under field conditions. Repeated measurement s on identical leaves over a time-course of 6 d demonstrated a strong age-d ependence in the capacity for the synthesis of UV-A screening compounds upo n exposure to UV-B radiation. It is concluded that the new method may provi de a valuable tool for the investigation of the acclimation of plants to UV -B radiation and, when accompanied by HPLC analysis, of the reaction of phe nolic metabolism to environmental stimuli.