Electrokinetic properties of thylakoids in in vitro cultured Gypsophila paniculata plants

In vitro cultured Gypsophila paniculata L. plants were used as a model to e valuate the effect of some cytokinins and anticytokinins on thylakoid surfa ce charge. Influence of the cytokinins N-6-furfurylaminopurine (kinetin) an d N-1-(2-chloro-4-pyridyl)-N-2-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 ( sigma), fluorescence induction kinetics and millisecond-delayed light emiss ion was studied. Our results showed that the chlorophyll (a+b) content sign ificantly 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 b ut so-called 'dilution of the pigments' was available. Anticytokinins inhib ited the formation of more than one shoot, and the chlorophyll content was not influenced significantly. The phenylurea cytokinin 4-PU-30 and anticyto kinins increased the electrophoretic mobility, zeta potential and surface c harge density of thylakoids after a longer time of treatment. Making thylak oid membranes more negatively charged, phenylurea cytokinin and anticytokin ins increased the aggregation of the complexes and the energization of the membrane. Our results showed that plant growth regulators decreased the pri mary photochemical activity of photosystem II (estimated by the ratio F-v/F -m) and delayed fluorescence intensity in the 1st month. However, no signif icant changes were observed in these parameters in the 2nd month.