EFFECT OF 2,4-DICHLOROPHENOXYACETIC ACID AND HABITUATION ON LIPID ANDPROTEIN-COMPOSITION OF MICROSOMAL-MEMBRANES FROM PERIWINKLE CELL-SUSPENSIONS

Investigations on biochemical changes associated with habituation in p lant cells and tissues grown in vitro are still Limited. In the presen t work, we have compared the lipid and protein composition of microsom al membranes prepared from two Catharanthus roseus cell lines: a 2,4-d ichlorophenoxyacetic acid (2,4-D)-dependent line and a fully-habituate d line selected from the former. In order to distinguish changes assoc iated with habituation from those associated with 2,4-D treatment, eac h line was grown for one passage in medium with or without 2,4-D. The auxin Provoked a lower amount of phospholipid, a higher free-sterol to phospholipid ratio, and a decreased fluidity in microsomal membranes, all parameters usually associated with cell senescence. On the other hand, habituation decreased the free sterol to phospholipid ratio, inc reased the oleic add to linoleic acid ratio and the sitosterol to camp esterol ratio. The fluidity of the membranes from habituated cells inc reased. Habituation, as well as treatment of the cells with 2,4-D, cha nged the polypeptide profiles of the microsomal membranes. The data le ad to the conclusion that membranes are targets for biochemical change s associated with habituation. They also support the hypothesis that s ome similarities exist between habituated cells and animal tumour cell s.