Primary leaves of barley (Hordeum vulgare L.) plants, growing either in complete (H) oř nitrogen deficient nutrítion (H-N), were subjected to complex chlorophyll (Chl) a fluorescence measurement after an 8 or 14 d cultivation period. Ilie fluorescence spectra of H-N plants exhibited a higher ratio of the two maxima F690/F73S, caused predominantly by drastic decrease in Chl content. The ratio of Chl to carotenoids (a+b/x+c) decreased considerably in H-N leaves. In špite of high Rfd values (ratio of fluorescence decrease) in H-N leaves, indicating high efficiency of photochemical energy conversion, quenching analysis of H-N leaves showed a significantly higher coefiicient of non-photochemicď quenching, qjsip (i.e. higher proportion of heat loss). Fast fluorescence kinetics indicated slower reoxidation of primáty quencher (Q^) in H-N leaves.