EFFECT OF MANNITOL AND GLUCOSE-INDUCED OSMOTIC-STRESS ON GROWTH, WATER RELATIONS, AND SOLUTE COMPOSITION OF CELL-SUSPENSION CULTURES OF POPLAR (POPULUS-DELTOIDES VAR OCCIDENTALIS) IN RELATION TO ANTHOCYANIN ACCUMULATION

A cell suspension culture of poplar (Populus deltoides (Marsh.) Bartr. var. occidentalis Rydb.), accumulating the anthocyanin pigment, cyani din 3-glucoside, in the lag phase of culture growth, was subjected to osmotic stress with glucose and mannitol. Osmotic stress treatments re sulted in growth suppression and higher anthocyanin accumulation compa red with unstressed cells. Both an increase in the proportion of pigme nted cells and an increase in the concentration of anthocyanin in the pigmented cells were responsible for high anthocyanin content of cultu red cells subjected to osmotic stress. The osmotic stress induced by g lucose suppressed growth more than that by mannitol and produced highe r anthocyanin levels. Only small amounts of [U-C-14]mannitol were take n up and metabolized by the cells. Stressed cells accumulated sugars a nd free amino acids to a different extent resulting in altered cell su gar-to-amino acid ratios. The accumulation of osmotically active solut es and cell growth suppression may both be responsible for the accumul ation of anthocyanin in stressed cells.