Effect of Ions on the Orientationof CorticalMicrotubules in Spirogyra Cells

Effects ef ions on the orientation of cortical microtubu]es (MTs) in spirogyra cells were studied. After depotymerization with amiprophos-methyl (APM), MTs were atlowed to reorganize in NaCl sollltions of yarious concentrations. As the conce"tration of NaCl increased, the frequency of ce]ls that had oblique MTs increased. When ce]ls in NaCl solution vvere transferred into artificia) pond water (APW) and incllbated for 6 h, a]1 the MTs changed to become transyerse to the longitudina] axis of the cetl. KCI and MgC12 also had effects on the orientation of MTs. However, NH4Cl, CaC12, CoCl2, and Co(N03)i did not show any effect. These results sugges"hat Na', K', and Mg2' haye effects on MT orientation and that NH4+, Cai+, Coi+, Cl-, and N03haye little effect. When MTs were reorganized in either NaCl or KCI solutions, al} the oblique MTs were organized into an S-helix. In contrast, some of the oblique MTs were fo"nd as a Z-helix in the cel]s incubated in MgC]2 or mannitol solutions. These results suggest that effects of Na' and K' on the orientation of MTs are not the same as those of Mg2' and mannitot. These results proyide the first eyidence that ions are inyolyed in the orientation of MTs in algae.