RESPONSE OF MERISTEM CELLS TO HYPEROXYGENATION

Cycle parameters were estimated in Allium cepa L meristems proliferating under steady state conditions in tap water aerated with either 21 or 100% O2 and containing 7.9 and 39.0 mg/1 of dissolved oxygen, respectively. Cycle time was slightly but consistently reduced under hyperoxygenation, as shown in synchronous cells labelled as binucleate following a short treatment with 5 mM caffeine. By autoradiography after 3H-thymidine treatment followed by microdensitometry of unlabelled interphases it was determined that cellular frequencies at the last third of the S period (S3) were statistically different (P<0.05) in control and hyperoxygenated conditions. Estimation of absolute timing confirmed that S3 duration was nearly halved under the increased O2 tension. Finally, G1 time was not modified by hyperoxygenation, though this cycle stage lengthened under hypoxia. © 1990.