Effect of Centrifugation on the Development and Timing of Premitotic Positioning of the Nucleus in Adiantum Protonemata

Abstract

When single-celled protonemata of Adiantum capillus-veneris L. were centrifuged immediately before transferring to darkness from continuous irradiation with red light, their nuclei were displaced basipetally. Both filamentous and branched protonemata were obtained. The stronger the centrifugal acceleration, the more frequently the branched protonemata were induced.The effect of centrifugation at 1,300xg for 15 min on nuclear displacement was different at different stages of the cell cycle. In early GI phase, the nucleus was easily displaced by centrifugation, but quickly returned to the original position after centrifugation. In late G I phase, the nucleus was displaced, but after centrifugation it never came back to the original position. In late Ge and M phases, the nucleus was no longer displaced by the centrifugation. Premitotic positioning of the nucleus in cytokinesis took place about 5 hr before cell plate formation in all centrifugal treatments described above.

A MORPHOLOGICAL STUDY OF BUD INITIATION IN THE BROWN ALGA SPHACELARIA FURCIGERA*†

“…It is generally accepted that the orientation of the nucleus and/or spindle is determined after the nucleus has completed its pre-mitotic migration (Mineyuki and Furuya, 1980). Our study supports this view as the original nuclear orientation was maintained during the pre-mitotic migration of the nucleus into the bud initial.…”

“…Our study supports this view as the original nuclear orientation was maintained during the pre-mitotic migration of the nucleus into the bud initial. The final nuclear orientation influences the orientation of the cross wall (Mineyuki and Furuya, 1980) and if this is so, then the orientation of the cell plate observed in stage VII would indicate that the nuclear orientation must have shifted by 90°j ust prior to karyokinesis. The basal, rather than lateral, position of the centrioles in the subtending sister axial cell (Fig.…”

Effects of hypergravity on the elongation and morphology of protonemata of Adiantum capillus-veneris

“…Basipetal centrifugation at 1 300 g for 15 min induced the displacement of the nucleus with resultant branching of the protonema. Under our hypergravitational conditions (from -13 to +20 g), no movement of intracellular components such as stratificatioti of chloroplasts and nuclei (Ootaki 1963) or displacement of the nuclei (Mineyuki and Furuya 1980) was found during light microscopic observations. It now seems important to examine the effects of hypergravity on the ultrastructure and, in particular, on the cytoskeleton of protonemal cells of Adiantum.…”

“…Although the force and duration of hypergravity differed between the experiments with A. capillus-veneris in this study and those with P. vittata (Ootaki 1963), the same dependence on the direction of hypergravity was noted with respect to the shape of protonemata in the two species. Mineyuki and Furuya (1980) also reported a branched form of Adiantutn protonetnata. Basipetal centrifugation at 1 300 g for 15 min induced the displacement of the nucleus with resultant branching of the protonema.…”

Preprophase Band in Fern Protonemata: Mechanism of Development and Comparison with Flowering Plants

“…&a (1961) displaced the nucleus of dividing Tradescantia stamen hair cells by centrifugation, but the nucleus moved back to the original site after centrifugation. However, Mineyuki and Furuya (1980) found that the nucleus did not come back to the original site after centrifugation in Adiantum protonemal cells, if the nucleus was displaced far enough from the original site.…”