Silver enhances stamen development in female white campion (Silene latifolia [Caryophyllaceae])

Sex expression in the dioecious plant white campion (Silene latifolia Poiret subsp. alba) appears to be insensitive to exogenous applications of auxins, cytokinins, gibberellic acid, and ethylene; however, silver thiosulfate (Ag 2S2O3), an ethylene inhibitor, enhanced stamen development in female white campion. In wild-type females, stamen development is arrested before the microspore mother cells are formed. In contrast, stamens of Ag2S2O3-treated females completed meiosis and produced microspores. Stamen development for these females was incomplete, however, and pollen did not mature. Ag2S2O3 stimulated stamen development to the same extent in asexual white campion mutants that retained a Y chromosome but had lost Y-linked genes needed for early stages of stamen development. Although Ag2S2O3 can inhibit ethylene signaling, the enhancement of stamen development in female white campion cannot be explained as a loss of ethylene response because no other ethylene inhibitor tested (1-methylcyclopropene, trans-cyclooctene, aminoethoxyvinylglycine, and cobalt chloride) caused stamens to develop in female plants. In addition, application of other metal ions could not enhance stamen development. Therefore, the effect we observed on female white campion was specifically caused by silver ions but not by their action on ethylene signaling.