CHLOROPHYLL FLUORESCENCE ANALYSIS OF GENOTYPIC VARIABILITY OF THE DROUGHT STRESS RESPONSE OF WHITE CLOVER (TRIFOLIUM-REPENS) AND PERENNIAL RYE (LOLIUM-PERENNE)

The genotypic variability of six interspecific neighbouring pairs of white clover (Trifolium repens L.) and perennial rye grass (Lolium perenne L.) has been examined in relation to chlorophyll fluorescence and leaf water content. Fluorescence was measured using wavelengths of 690 and 730 nm. The following indices of fluorescence were used: the fluorescence-decrease ratio at the two wavelengths (vitality index), their combination (adaptation index), and the ratio of the fluorescence intensities at 690 and 730 nm. The effect of the type of drought stress applied on leaf cutting and pot planted material was examined. The results show that the first two indices of fluorescence are precocious indicators of drought stress and that they allow to distinguish genetically close individuals. Fluorescence thus provides a mean of ranking genotypes of two species.