CELL-DIVISION AND MICROCOLONY FORMATION IN PROTOPLASTS FROM MATURE MATERIAL OF HYBRID LARCH (LARIX X EUROLEPIS HENRY)

Protoplasts were isolated from needles of in vitro shoots initiated fr om short shoot buds of stecklings from an 8-year old hybrid larch (Lar ix x eurolepis Henry) tree. Protoplast yield and viability have reache d, respectively 8.8 x 10(5) protoplasts/g fresh weight and 91.8% when needles were enzymatically digested for 16 h in osmoticum containing 0 .5% Cellulase R-10, 0.5% Macerozyme R-10 and 0.5% BSA. First cell divi sions were observed after 2 days of culture in a modified liquid (or s olid) Murashige and Skoog medium (MSG) containing 2 mg/l 2,4-D and 0.5 mg/l BAP. After 1 week, 15-25% of the protoplasts had divided, and so me had formed microcolonies with a plating efficiency from 3.9-7.9%. P rotoplast-derived cells which had undergone division were concentrated mainly in size classes between 25.0 and 44.5 mu m, and division frequ ency increased with diameter.