Abstract: Poplar NL-80106 (Populus deltoides×P, simonii) mesophyll protoplasts were isolated from leaves of 30 days-old sterile shoot, with 4 × 107/g fr. wt of protoplast yield after purification. The protoplasts were cultured in KM8p and MS liquid media containing 2 mg/L 2, 4-D, 0. 5 mg/L NAA and 0.5 mg/L KT. Higher plating density and lower osmatic pressure (0.45 mol/L) were proved to be favourable to division of protoplast-derived cells. The first division initiated 5 days after culture, and the division frequency reached 4.5 % on the 10th day. A number'of cell colonies and microcalli was formed in 12 weeks. Using organic nitrates and glucose in protoplast culture medium was beneficial to increase division frequency and plating efficiency. The calli were allowed to grow to 4--6 mm in height with red colour and compact structure on the gelrite-sohdified NLZ1 proliferation medium in 3 weeks and were transferred onto NLF differentiation medium where the frequency of shoot formation could reach 100%. The 3 cm high shoots were then cut off from the callus and rooted on 1/2 MS medium.

Key words: opulus deltoides × P. simonii, Protoplast culture, Plant regeneration