Settling of Equisetum Telmateia Ehrh. Bymeans of Gametophyte Culture

Abstract

One can marvel at why Equisetum telmateia, our most decorative horsetail, is not met in parks or gardens. Perhaps it has been tried several times to settle it on a desired place by transplanting rhizomes. MEUSEL et al. (1971), however, write that it is practically impossible to do so, because the rhizomes will rot after transplanting instead of developing new shoots. All attempts made by this author had negative results. Another method, which proved successful, consists of culturing gametophytes and growing the developing sporophytes in flower pots for one year or more, after which they can be transplanted in the open air. This method is briefly described.Mature spores of E. telmateia were collected from a stand in Beek, East of Nijmegen, the Netherlands, in April 1973 and the end of March 1974. Several sowings were carried out on a modified mineral Knop-medium containing 1 per cent agar. This medium, described by LAROCHE (1968) and used by him for the culture of gametophytes of E. arvense, contains twice as much Ca(N0 3 h as Knop-medium and was used at one third of the usual concentration. No micro-elements were added; the water consisted of 50% demineralized water and 50% tap water. After sterilization the agar was poured into petri-dishes in relatively thick layers of 7 mm in order to prevent excessive loss of water potential.The germination results were very variable. Freshly harvested spores from April 1973 did not germinate at all; even after some time no germination was observed. However, when a sample of the same spores was stored at 4°C for 4 days, approximately two third of the spores germinated within 48 hours at room temperature. When spores cooled for 4 days at 4°C, were warmed for approximately one hour at room temperature and subsequently once more subjected to one night at 4°C the germination reached approximately 75% within24 hours.In 1974 several cool nights had preceded the date of collection of the spores and subsequent germination of the different sowings showed less variability. The dishes were placed in a temperature-controlled room at 24°C under continuous light, supplied by fluorescent tubes (Philips TL, M40Wj33 RS), with an intensity of 5500-flOOO lux at plant level. The gametophytes of E. telmateia developed relatively rapidly. After 3 to 4 weeks the young plantlets were transplanted from the agar with tweezers into petri-dishes containing a 7 mm layer