EFFECT OF IN-VITRO STORAGE AT 4-DEGREES-C ON SURVIVAL AND PROLIFERATION OF POPLAR SHOOTS

Shoot explants of in vitro proliferating cultures of Populus tremula (L.) x Populus tremuloides (L.) were stored for three months at 4 degrees C, in dark or light, in basal culture medium with or without 2-isopentenyladenine (2iP), and in rooting medium with naphthalene acetic acid. They were transferred to cold at different times after subculturing. One hundred percent of shoots survived all tested conditions, in spite of leaf brewing and necrosis. After transfer to 24 degrees C for 2 weeks and a normal multiplication cycle, the shoots proliferated at a rate similar to controls or at a higher rate in the case of shoots introduced into the cold 7 or 14 days after subculture and stored in dark on medium containing 2iP.