Turgor pressure regulation and the orientation of cortical microtubules inSpirogyra cells

Microtubules (MTs) of cells of Spirogyra sp, were depolymerized by treatmen t with amiprophos-methyl(APM) for 1 h and then reorganized in 0.30 M mannit ol solution. The reorganized MTs after 1.5 h incubation showed an oblique/l ongitudinal orientation and then became transversely oriented as the incuba tion was prolonged, During this incubation, the osmotic pressure of cells w as measured by the plasmolysis method. The cell osmotic pressure increased with time. The calculated turgor pressure at 1.5 h was 0.11 M (mannitol equ ivalent) and, at 13.5 h, 0.25 M. Similar changes in MT orientation and reco very of the turgor pressure were also observed in 0.30 M sorbitol solution. These results suggest that the MT orientation may be correlated with the t urgor pressure. Among fresh water algae sensitive to a saline environment, this Spirogyra w as the first species shown to have a turgor regulating mechanism, although the recovery of turgor pressure was incomplete. The recovery of turgor pres sure in mannitol solutions was also observed without APM treatment.