HIGH-LEVEL OF ENDOGENOUS CYTOKININS IN TRANSGENIC POTATO PLANTLETS LIMITS PHOTOSYNTHESIS

Introduction of the gene for cytokinin synthesis into potato genome le ad to a manifold increase in the level of cytokinins (zeatin, zeatin r iboside, isopentenyladenine, isopentenyladenosine) in plantlets grown in vitro. The increasing cytokinin level was associated with increasin g tendency to teratoma formation, to decreasing leaf net photosyntheti c rate and to increasing dark and light respiration rates and CO2 comp ensation concentration. During plantlet (or teratoma) ontogeny, net ph otosynthetic rate increased simultaneously with the decrease in cytoki nin level. High level of endogenous cytokinins was associated also wit h lower photochemical activities of both photosystems in isolated chlo roplasts.