Ex Vitro Phenotype Stability is Affected by In Vitro Cultivation

Plant phenotype stability during ex vitro growth, one of the main requirements of plant micropropagation, was tested on tobacco. Plants cultivated in vitro in the presence of 3 % sucrose under photon flux density (PFD) of 200 mol m^–2 s^–1 (3 % HL plants) showed the best growth and photosynthetic parameters in the course of 7-day acclimation. However, significant change in phenotype of these plants appeared under a decrease in PFD to 50 mol m^–2 s^–1 during further ex vitro growth (in the period of 7^th – 17^th day). Much higher internodia elongation was found in 3 % HL plants in comparison with plants grown in vitro on sucrose media under PFD of 50 mol m^–2 s^–1 (3 % LL) or without sucrose either under PFD of 50 mol m^–2 s^–1 or 200 mol m^–2 s^–1 (0 % LL, 0 % HL). It can be presumed that 3 % HL plants show permanent demand for high PFD. Neither ABA or chlorophyll contents nor de novo thylakoid membrane synthesis were related to the morphogenic effect of low PFD. Changeable contents of hexoses in leaves of 3 % HL and 3 % LL plants were in no direct correlation to the elongated growth.