Photosynthesis in different types of transgenic tobacco plants with elevated cytokinin content

Photosynthetic parameters were compared in three types of transgenic tobacco plants: ipt-transgenic plants with slightly elevated endogenous cytokinin (CK) content, Pssu-ipt-transgenic plants with markedly increased CK content, and zmp-transgenic plants with slightly elevated CK content accompanied by elevated auxin content, Slightly increased CK content promoted net photosynthetic rate (P-N) in both ipt- and zmp-transgenic plants, and chlorophyll (Chl) and carotenoid contents in zmp-transgenic plants, Morphology, growth characteristics, stomatal conductance, and parameters of Chl a fluorescence kinetics were similar in control and transgenic plants with slightly higher CK content. No significant effect of increased level of endogenous auxin (indole-3-acetic acid) on development of zmp-transgenic plants and measured parameters was found. Pssu-ipt-transgenic plants with highly increased CK content revealed suppressed root development, wilting of plants, and depression of P-N and stomatal conductance; however, Chl content was slightly increased and parameters of Chl a fluorescence kinetics did not indicate damage to photosynthetic apparatus.