Determination of Rhizoid Orientation by Light and Darkness in Germinating Spores of Onoclea Sensibilis

Abstract

When spores of the fern, Onoclea sensibilis L., are allowed to germinate in darkness, the rhizoid and the protonema are positioned at close to a right angle. If the spores are exposed initially to light and allowed to germinate, the rhizoid and protonema are positioned nearly axially, at opposite ends of the spore. The greater the duration and intensity of the initial illumination, the greater the tendency towards axial arrangement. All colors of light are active to some degree, and the effects are intensity‐dependent. The response occurs in a uniform light field and is not dependent on a directional stimulus; the phenomenon reflects the relative arrangement of one part of the gametophyte to another part but not the orientation of growth with respect to an external stimulus. Direct tests show that neither the relative rhizoid orientation nor initial polarity of germination are affected by unilateral white light or polarized red light; the subsequent growth of the protonema, however, is oriented perpendicular to the plane of light polarization. The effects of light in determining the positional relationship between rhizoid and protonema are interpreted in terms of a hypothesis proposing light‐induced changes in the structure and mechanical properties of the spore wall.

Control of Mitosis by Phytochrome and a Blue-Light Receptor in Fern Spores

“…The nucleus remained near the corner of tetrahedronshaped dormant spores and dark-incubated spores. In contrast to a previous observation of spores of O. sensibilis (Miller and Greany, 1974), there was no evidence of any nuclear movement during imbibition for 167 h.…”

“…The nuclei in germinating spores of the fern O. sensibilis were reported to move from the center to the corner of spores prior to the first mitosis (Miller and Greany, 1974). If this movement was prevented, no differentiation of a rhizoid occurred during the subsequent mitosis (Miller and Greany, 1976).…”

“…capillus-veneris (Iino et al, 1989) and Dryopteris paleacea (Dürr and Scheuerlein, 1990). In addition, a nucleus sits in the center of each dormant spore of Onoclea sensibilis, but when the spores are hydrated and exposed to red light, the nucleus moves to a corner of each spore, with the consequent asymmetric division of the cells (Miller and Greany, 1974).…”

Promotion of Fern Rhizoid Elongation by Metal Ions and the Function of the Spore Coat as an Ion Reservoir

“…Spore-bearing fronds of Onoclea sensibilis were collected near Jericho, VT in early spring of 1980 and were stored in plastic bags under refrigeration. The methods of spore isolation are described by Miller and Greany (19).…”

“…Dry spores were sown on the surface of about 5 ml liquid medium contained in 25 x 100-mm glass culture tubes which were closed with loose fitting aluminum caps. The culture solution was either Knop's medium (19), glass-redistilled H20, or solutions of different metal salts prepared in glass-redistilled H20 from reagent grade chemicals. The following salts were used: Ca(NO3)2.4H20, MgCl2.6H20, Sr(NO3)2, MnCl2-4H20, FeCl3.6H20, NaCl, KCI, Ni(NO3)2.6H20, Co(NO3)2.H20, ZnCl2, and AlCl3-6H20.…”