CIRCULAR ARRANGEMENT OF CORTICAL MICROTUBULES AROUND THE SUBAPICAL PART OF A TIP-GROWING FERN PROTONEMA

Cortical microtubule arrays in tip-growing protonemal and rhizoid cells of the fern Adiantum gametophytes were observed by immunnofluorescence microscopy. A circular arrangement of cortical microtubules was demonstrated around the subapical part of protonemal cells growing under red light conditions. However, such an arrangement was not found in growing rhizoids either by immunofluorescence microscopy or by electron microscopy. The different patterns of microtubules arrays around the apices of tip-growing protonemal and rhizoid cells suggest the possible existence of different mechanisms in regulating the cell diameter in the two types of cylindrical cell.