Long term in vitro-cultured plant cells show typical neoplastic features at the cytological level.

Cells from a green normal (dependent on exogenous hormones) callus and from an achlorophyllous fully habituated (independent from exogenous hormones) callus, both generated from the same sugarbeet strain more than twenty years ago, were reexamined cytologically, ten years after the first comparative description. Cells from the habituated callus, already considered as neoplastic cells, because terminating a neoplastic progression where the organogenic totipotency was lost, still showed nuclear invaginations, polynucleolation, vacuolation of nucleoli and incomplete cell walls, nevertheless at a higher degree. The present study particularly shows that, compared to their previous description, normal cells have started to acquire some features (polynucleolation, nuclear invaginations.) that are typical of the neoplastic cells. This suggests that normal cells, on the long term, also entered a neoplastic progression, which should explain the known progressive loss of regeneration capacity of too long subcultured hormone-dependent calli.