| Abstract: | Application of pulse-amplitude-modulation (PAM) fluorometers for measuring slow stages of chlorophyll fluorescence induction (CFI) is considered. With an example of Triticum aestuvum L. plants grown under continuous illumination at a photon flux density of 600 μmol/(m2 s) photosynthetically active radiation (PAR), the CFI curves were analyzed with leaves of various ages as a function of actinic light intensity. The fluorometer PAM-2100 was applied for measurements of CFI curves. The characteristic peaks of CFI curves in wheat leaves were most conspicuous and had the largest amplitudes at 600–800 μmol/(m2 s) PAR, which corresponds to the middle range of actinic light intensities employed in PAM-2100 fluorometers. In plants exposed to favorable and stressful conditions, the developmental stages may proceed at different rates; thus, the comparison of fluorescence parameters for leaves of equal calendar age but having different physiological states may provide ambiguous data. Therefore, the feasibility of recording CFI curves of different types is quite important for rapid diagnostics of the age and state of plant leaves, as well as for adequate physiological conclusions. |
