Ethylene and carbohydrate requirements for apogamous bud induction in Pteridium gametophytes

Abstract

Periodic evacuations of culture vessels containing Pteridium gametophytes to reduce the concentration of endogenous ethylene within the tissue, followed by reinfiltration with air, yielded a 99% reduction in apogamous budding as compared to the ethylene-reinfiltrated control. Growing gametophytes in increasing concentrations of carbon dioxide, a competitive inhibitor of ethylene, caused decreases in the apogamous response. Apogamy was completely eliminated by 7% carbon dioxide, without inhibiting gametophytic growth. Adding 1 μl/liter ethylene to each concentration of carbon dioxide reversed the inhibition and some apogamy did occur in gametophytes grown in 7% carbon dioxide supplied concomitantly with the exogenous ethylene. A carbohydrate is required for ethylene-induced apogamous bud induction. Growth of gametophytes in the presence of ethylene on medium lacking sucrose for extended experimental periods was not sufficient to cause induction. Total gametophytic growth on media containing various concentrations of sucrose was not affected by the presence or absence of ethylene in the atmosphere surrounding colonies. These results demonstrate that both ethylene and a utilizable carbohydrate are required for apogamy.