Metabolic suffering in Actinidia deliciosa callus growing medium

Calluses of Actinidia deliciosa wcre grown in successive 45-days subcu[tures in Gambors as medium (20g/l sucrosese). In order to evaluate the changes that take place during tbe growth of the callus, we measured , at different times (10, 35 and 45 days), the incease in fresh weight, the respiratory activity, the levels of inorganic caltions (K+' Na+, Ca2+ and Mg2+) and of some metabolites (sucrose, giucose-6-P, malicc acid. amino acids and adenylic nudeotides). After an cxponential growing phase (0- 10 days), the callus growth rate became practically constant up (0 the 45th day. In the first period the anaIyzed metabolic parameters reached levels that remained pratically constant up the 35~ day. In the last period the level level and the respiration rate greatly decreased while the ATP/ADP ratio increased; K+, Ca2 + and Mg2+. slightly decreased while Na + greatly increased. Upon transfer onto fresh medium, the above cited parameters returned 10 the former levels, suggesling prompt recovery of the calluses. It is interesting to point oul that in the last period of incubation important metabolic changes take place. even if the growth rate is not affected. This might play an important role in micropropagation and selection of the cultures, and should be taken into account in the: setting up of the culture prococols.