Extending the Viability of Equisetum hyemale Spores

Abstract

The green spores of Equisetum normally are viable for only short periods of time. Thus, these spores are available to produce gametophytes for brief periods during the year in many parts of the world. Over the years efforts have been made to keep the spores viable for extended periods of time. In this study, ripe cones of E. hyemale were stored frozen at -70?C. This procedure extended the viability of the spores for more than a year, and 37% of the spores stored frozen for a year germinated and formed gametophytes. Green spores of pteridophytes usually have short viabilities and some of the shortest are reported for Equisetum (Lloyd and Klekowski, 1970). The best possibility to obtain substantial spore germination is to use spores from re- cently opened cones (Hauke, 1969). Fresh spores are easier to collect from tropical species of Equisetum because ripe cones are available essentially all year (Hauke, 1969). This is not the case for species from the temperate zone, because their cones are ripe for only short times during the growing season. Outside the tropics, fresh Equisetum spores are unavailable for most of the year. Efforts have been made to extend the viability of Equisetum spores so that living spores are available for a greater portion of the year. Castle (1953) stored sporangia and spores of E. arvense in a sterile nutrient solution at 5?C. Spores stored in this manner remained viable for three months. Hauke (1969) tried freezing dry and wet spores or storing wet spores at 80C. The best of these procedures, wet spores at 8?C, kept the spores of E. myriochaetum alive for 1.5 months. Duckett (1970a) stored ripe cones of E. arvense in sterile nutrient solutions at 4?C. Germination was obtained after two months of storage but none occurred after five months. Jones and Hook (1970) placed freshly shed spores of E. telmateia in bottles, added 2-3 cm of glycerine, capped the bottles, and stored them at -10?C. The percentages of germination were 54, 74, and 37 for spores stored under these conditions for 1, 2, and 3 years respectively. The technique of Jones and Hook (1970) was superior to the others for main- taining the viability of Equisetum spores. However, recovering the spores from the glycerine is somewhat involved. The spores have to be washed out of the glycerine with nutrient solution or water before they can be placed in culture. The present study was carried out in an effort to devise a simpler procedure for storing and sowing Equisetum spores.