Phytochrome-Mediated Mitotic Activity and Induction of two-Dimensional Growth in Gametophytes of Anemia phyllitidis (L.) Sw. *

Abstract

Summary In non-growing protonemata of Anemia phyllitidis mitotic activity can be induced with a single s-min red light pulse that is abolished by brief far red light, indicating phytochrome control. After repeatedly raising the Pfr to a high level with red light pulses (e.g. one pulse every 4 days) some 10 % of gametophytes respond with transition to 2-D growth, which is first apparent in a drastic reduction of the L/B ratio of apical cells ( fr level with brief far red light immediately following red light not only totally prevents a reduction of cell growth but causes a considerable promotion of cell extension growth, which eventually leads to transverse cell divisions. Induction of 2-D growth with red light pulses also occurs in non-growing cells derived after R-pulsed (instead of continuous red light) induction of spore germination; the light treatment of spores must only be so sufficient as to establish a high enough number of protonemata for subsequent experimentation. The slow escape reaction from far red reversibility of red light-induced mitotic activity suggests mediation by a stable form of phytochrome, which appears to be different from that controlling spore germination.