Poplar acclimation to cold during in vitro conservation at low non-freezing temperature: metabolic and proteic changes

Microcuttings of Populus tremula L. were successfully in vitro conserved for more than 1 year at 10 °C on Murashige and Skoog (MS) medium devoid of any growth regulator. During storage, an important limitation of growth was observed. Survival was unaffected and the recovery of multiplication ability after transfer to normal conditions was satisfactory. From the first days of treatment microcuttings cultured at 10 °C when compared with cultures grown at 23 °C presented important biochemical changes. Endogenous contents of ABA and proline were affected during cold exposure as well as activities of several free radicals scavenging involved enzymes such as superoxide dismutase (SOD), dehydroascorbate reductase (DHAR) or glutathione reductase (GR). Moreover, de novo synthesis and accumulation of two new proteins with a molecular weight of about 120 kDa were observed after 3 days of chilling treatment.