Effect of benzyladenine, 4-PU-30 and thidiazuron on millisecond delayed and prompt chlorophyll fluorescence of Dianthus caryophyllus L. axillary buds cultured in vitro

Abstract The effects of benzyladenine (BA) and two phenylurea cytokinins ( N -phenyl- N ′-(2-chloro-4-pyridyl)urea (4-PU-30) and thidiazuron (TDZ)) on in vitro cultures of carnation were studied using induction kinetics and thermograms of prompt and delayed chlorophyll fluorescence. In plantlets obtained from explants cultivated on a medium with 0.4 μM BA or 0.04–0.004 μM phenylurea cytokinins, the photosynthetic apparatus showed high PS II photochemical activity comparable to control without cytokinins and 5.8–97.5% higher estimated photoinduced transmembrane proton gradient (low concentrations of 4-PU-30 are especially effective). At a concentration of 0.4 μM, when compared to BA treatment, phenylurea cytokinins induced 24–35% suppression of photochemical activity, 44–46% suppression of estimated transmembrane proton gradient and 12–17% suppression of estimated electron transport rate. It is likely that this concentration of phenylurea cytokinins exceeded the optimal dose. The analysis of the same luminescent characteristics in the presence of different 4-PU-30 and TDZ concentrations showed that these compounds induced dose-dependent changes in the functional activity as well as alteration in the level of energization of the thylakoid membrane. When fluorescence thermograms were evaluated, phenylureas appeared to change the high-temperature stability of the photosynthetic apparatus.