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 wa s conducted on MS medium with 30 kg m(-3) sucrose or on hydroponic medium ( containing less mineral salts), under higher photosynthetic photon flux den sity (PPFD) (100 in comparison with 45 mu mol m(-2) s(-1)) and flushed by a mbient air [AC, 340 mu mol(CO2) mol(-1)] or by CO2-enriched air (EC, 2 500 mu mol mol(-1)) and lower relative humidity (80-90 % vs. 96-99 %). This cul tivation led to plantlets with longer roots and adventitious root formation . Net photosynthetic rate and ribulose-1,5-bisphosphate carboxylase/oxygena se (RuBPCO) activities, RuBPCO/phosphoenolpyruvate carboxylase activities r atio, and starch accumulation increased under these conditions. After 14 d, plantlets had functional stomata and could be acclimated on open benches w ithout gradual decrease in relative humidity. The percentage of survival wa s higher when the rooting took place in EC than in AC. However, the advanta ge acquired during rooting phase by plantlets cultured in liquid medium was not maintained after 4 weeks of acclimatisation.