The Effect of Surface Sterilization on Cultures of Ceratopteris richardii Gametophytes

Abstract

Gametophytes of Ceratopteris richardii were grown as single-spore and double spore cultures on agar to test the effects of surface sterilization of spores (with bleach) and contamination of cultures on growth and sexual expression. Hermaphroditic gametophytes were larger in double- spore than in single-spore cultures for cultures derived from both untreated and sterilized spores, whereas gametophytes were larger in single-spore than in double-spore cultures in contaminated cultures. However, gametophytes did not differ in size between double-spore and single-spore cultures derived from surface sterilized spores. The greatest antheridiogen response was observed in cultures with no treatment and the least antheridiogen response was observed in contaminated cultures. A standard method of preparing gametophyte cultures from spores involves the surface sterilization of spores using a dilute bleach (hypochlorite) solution (e.g., Banks et al., 1993). The purpose of this method is to reduce the effects of other organisms on treatments during experimental investigations of ga- metophyte growth and development. We, however, have been concerned that bleach may affect the extracellular matrix of the spore. An effect on the extra- cellular matrix of the spore could significantly affect investigations of aspects of gametophyte development such as antheridiogens, as antheridiogens must first affect the extracellular matrix of a spore or gametophyte cell to have an effect on spore germination and gametophyte development. To address the effects of contamination and surface sterilization of spores, we cultured ga- metophytes of the leptosporangiate fern Ceratopteris richardii Brongn. using untreated and surface sterlized spores, culturing untreated spores in both axe- nic and contaminated media.