Comparison of plantain plantlets propagated in temporary immersion bioreactors and gelled medium during in vitro growth and acclimatization

The current work compared the physiological characteristics of plantain (Musa AAB) plantlets micropropagated in temporary immersion bioreactors (TIB) and on a gelled medium (GM). The plantlets were evaluated during in vitro growth (in the shoot elongation phase) and at the end of ex vitro acclimatization. TIB improved rooting and gave rise to longer shoots and higher dry mass. Respiration rate was the highest at the beginning of shoot elongation in both the TIB and GM plantlets. Photosynthetic rate in TIB was significantly higher than in GM from the midpoint of acclimatization, whereas a pyruvate kinase (PK) activity was lower. Starch accumulation was ca. two fold higher in corms than in leaves and always higher in the TIB than GM plantlets. The higher expression of genes coding for carbon metabolism enzymes PK and phosphoenolpyruvate carboxylase (PEPC) in TIB than in PM indicates a more important role of an autotrophic metabolism in the TIB plantlets when compared to the GM ones. The accumulated reserves were used during the first days of acclimatization leading to the higher survival rates and to the better plant quality of the TIB plantlets.