Ex vitro acclimatization of plantain plantlets micropropagated in temporary immersion bioreactor

Plantain (Musa ABB CEMSA 3/4) plantlets were micropropagated in temporary immersion bioreactors (TIB) or in gelled medium (GM). After ex vitro transfer ROS accumulation was determined by infiltrating leaves with nitroblue tetrazolium (NBT) and 3,3’-diaminobenzidine (DAB). Stomatal cells were more stained with NBT and DAB in GM plants than in TIB plants, but the difference disappeared at the end of acclimatization. At the end of the in vitro phase, GM plantlets showed higher activities of ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR), while activities of catalase (CAT), superoxide dismutase (SOD) and glutathione transferase (GT) were higher in TIB grown plantlets. At the end of acclimatization GT, SOD, CAT and MDHAR stabilized at low values of activity in plantlets derived from both treatments. Concerning the correspondent genes, GM plantlets showed higher expression of all transcripts with the exception of CuZnSOD. The immunobloting of peroxiredoxins (PRXs) showed that chloroplast-located PRXs were expressed at higher levels in TIB plantlets, some showing polymerization. In conclusion, TIB grown plantlets had an improved anti-oxidative response when compared with GM