Electrokinetic properties of thylakoids in in vitro cultured Gypsophila paniculata plants

In vitro cultured Gypsophila paniculata L. plants were used as a model to evaluate the effect of some cytokinins and anticytokinins on thylakoid surface charge. Influence of the cytokinins N-6-furfurylaminopurine (kinetin) and N1-(2-chloro-4-pyridyl)-N2-phenylurea (4-PU-30), cytokinin antagonists 2-chloro-4-cyclobutylamino-6-ethylamino-1,3,5-triazine and N-(4-pyridyl)-O-(4-chlorophenyl) carbamate on the pigment content, surface charge density (s ), fluorescence induction kinetics and millisecond-delayed light emission was studied. Our results showed that the chlorophyll (a+b) content significantly decreased after the 1st and the 2nd month of G. paniculata growth in the presence of the cytokinins kinetin and 4-PU-30. In our model system, cytokinins enhanced the number of open lateral buds and, as a consequence, more shoots per explant. Hence, chlorophyll synthesis was not inhibited but so-called ‘dilution of the pigments’ was available. Anticytokinins inhibited the formation of more than one shoot, and the chlorophyll content was not influenced significantly. The phenylurea cytokinin 4-PU-30 and anticytokinins increased the electrophoretic mobility, zeta potential and surface charge density of thylakoids after a longer time of treatment. Making thylakoid membranes more negatively charged, phenylurea cytokinin and anticytokinins increased the aggregation of the complexes and the energization of the membrane. Our results showed that plant growth regulators decreased the primary photochemical activity of photosystem II (estimated by the ratio Fv/Fm) and delayed fluorescence intensity in the 1st month. However, no significant changes were observed in these parameters in the 2nd month.