ABSTRACT
The slow fluorescence induction produced in cucumber leaves by light in the range of wavelengths 380-540 nm and intensity of 180 W/m2 was studied. The ratio of fluorescence maxima in the red region (F734/F682) in young and mature leaves was approximately 2. It is assumed that this value depends on an increase in the contribution of the long-wavelength fluorescence due to the spillover effect. In plants grown under natural conditions, the parameter F734/F682 correlated with the concentrations of chlorophyll and carotenoids. In plants grown in the light of red and blue regions no such correlation was observed and the F734/F682 remained unchanged. It is concluded that the F534/F682 is affected by the intensity and spectral composition of exciting light used during the growing.