Growth, Stomatal Conductance, Photosynthetic Rate, Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase and Phosphoenolpyruvate Carboxylase Activities during Rooting and Acclimatisation of Rosa Hybrida Plantlets

The rooting of shoots of micropropagated Rosa hybrida cv. Madame Delbard was conducted on MS medium with 30 kg m−3 sucrose or on hydroponic medium (containing less mineral salts), under higher photosynthetic photon flux density (PPFD) (100 in comparison with 45 µmol m−2 s−1) and flushed by ambient air [AC, 340 µmol(CO2) mol−1] or by CO2-enriched air (EC, 2 500 µmol mol−1) and lower relative humidity (80–90 % vs. 96–99 %). This cultivation led to plantlets with longer roots and adventitious root formation. Net photosynthetic rate and ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPCO) activities, RuBPCO/phosphoenolpyruvate carboxylase activities ratio, and starch accumulation increased under these conditions. After 14 d, plantlets had functional stomata and could be acclimated on open benches without gradual decrease in relative humidity. The percentage of survival was higher when the rooting took place in EC than in AC. However, the advantage acquired during rooting phase by plantlets cultured in liquid medium was not maintained after 4 weeks of acclimatisation.