Abstract
In Spirogyra, terminal cells differentiate to be rhizoids. Rhizoids are formed by repeated branching. In the presence of oryzalin, a microtubules depolymerizing drug, spherical rhizoids are formed. DCB, a cellulose synthesis inhibitor, caused burst at the tip of rhizoids. Synthesis of callose was not inhibited by DCB. This result indicates that cellulose synthesis is necessary for rhizoid elongation. Next, we observed the cellulose microfibrils. In the inner surface of the rhizoid, bundled microfibrils were observed, and those orientations were independent of microtubules. In the swelled rhizoid caused by oryzalin, bundled microfibrils were also observed. On the other hand, in the tip of the rhizoid, the microfibrils oriented to the same direction of as that of microtubules. We suggest that orientation of cellulose microfibrils at the tip region has a vital role in rhizoid morphogenesis.
