Branch formation induced by microbeam irradiation ofAdiantum protonemata

Branches were induced in centrifugedAdiantum protonemal cells by partial irradiation with polarized red light. Nuclear behavior and microtubule pattern change during branch formation were investigated. A branch formed at any part where a red microbeam was focused along a long apical cell. The nucleus moved towards the irradiated area and remained there until a branch developed. The pattern of microtubules changed from parallel to oblique at the irradiated area and then a transverse arrangement of microtubules appeared on both sides of the area. It appeared as if the nucleus was suspended between two microtubule rings. This nuclear behavior and the changes in microtubule pattern were different from those observed during branch formation under whole cell irradiation. From the results of this work we suggest that there is an importance for precise control of experimental conditions.