EFFECT OF CYTOKININS ON PHOTOSYNTHETIC PIGMENTS AND CHLOROPHYLLASE ACTIVITY IN IN-VITRO CULTURES OF AXILLARY BUDS OF DIANTHUS-CARYOPHYLLUS L

The effect of benzyladenine (BA) and two phenylurea cytokinins, N-phen yl-N'-(2-chloro-4-pyridyl)urea (4-PU-30) and thidiazuron (TDZ), on the growth, photosynthetic pigment content, and activity of chlorophyllas e (chlorophyll-chlorophylliodhydrolase, EC 3.1.1.14) of in vitro cultu res of carnations was studied. All cytokinins caused a rise in the fre sh weigth and a drop in the dry weight of leaf mass produced by the ex planted buds. Both 4-PU-30 and TDZ increased the chlorophyll content a nd this correlated with changes in chlorophyllase activity. The effect of 4-PU-30 and TDZ was similar to that caused by BA but at 10-fold or 100-fold lower concentrations. The application of higher concentratio ns of the phenylurea cytokinins caused an increase in the chlorophyll a/chlorophyll b ratio. However, at equimolar concentrations, the purin e and both phenylurea cytokinins had opposite effects, probably indire ct and related to some malformations caused by phenylureas. 4-PU-30 in creased, but TDZ decreased, photosynthetic membrane stability, which a rgues for a different molecular organization of the chloroplast membra nes.