Dark-Grown Psilotum

Abstract

Sporophytes of Psilotum are slow growing plants. This may be one reason why Psilotum has been subjected to very few experimental investigations. Marsden and Wetmore (1954) found that the apices of aerial stems grown in axenic culture often differentiated into rhizome apices. Rouffa (1966) observed that Psilotum, which was illuminated with cool white fluorescent light at 200-400 ft.-c. for extended periods of time, would produce unusual fertile appendages. Warren H. Wagner, Jr. (pers. comm., 1986) observed unusual plants of Psilotum collected in Hawaii by Francis G. Howarth on the floor of a lava tube in complete absence of light. These plants had the appearance of short aerial rhizomes. The modifications of these plants were apparently caused by their growth in the dark, so Wagner suggested that such modified development might be produced experimentally by giving greenhouse-grown plants a dark treatment. The aim of this investigation was to determine whether Psilotum plants could grow at all for an extended period in the dark and whether their morphology would be altered by such growth.