VARIATION OF THE QUENCHING OF CHLOROPHYLL FLUORESCENCE UNDER DIFFERENT INTENSITIES OF THE ACTINIC LIGHT IN WILDTYPE PLANTS OF TOBACCO AND IN AN AUREA MUTANT DEFICIENT OF LIGHT-HARVESTING-COMPLEX

Photochemical quenching, non-photochemical quenching, ratio of fluorescence decrease and several other chlorophyll fluorescence parameters have been studied for two types of tobacco (Nicotiana tabacum L.). The wildtype plant with dark-green leaves is compared with an Aurea mutant with light-green leaves characterized by a lack of light-harvesting pigment-protein complex. Fluorescence parameters have been determined under different intensities of the actinic light (6, 24, 100, 200, and 2460 mu mol m(2) s(-1)). The data are discussed in view of their importance for the characterization of the photosynthetic activity and the size of antenna systems. Based on the observation of this study a new type of ''relative'' quenching coefficients is proposed. Since these coefficients (in contrast to other quenching coefficients) all refer to the same reference F-M-F-O' they can be summed up and compared on a common scale ranging between zero and one. They thus provide a better understanding of the energy balance between photochemistry, chlorophyll fluorescence and heat production.