Reproduction and progeny of Silene latifolia (Caryophyllaceae) as affected by atmospheric CO2 concentration.

Sexual dimorphism in plants has been known for over two millennia. However, little is known about how male and female reproduction of dioecious species will respond to anthropogenic environmental perturbations. Using growth chambers, the effects of CO(2) enrichment on male and female reproduction in Silene latifolia were examined and whether parental CO(2) environment affected progeny germination and sex ratio. Reproduction of male and female S. latifolia was enhanced by a similar magnitude at elevated CO(2). Over the growing season, males produced 16 times as many flowers as females did fruits per plant, but no difference in reproductive biomass between genders was observed at ambient or elevated CO(2). Germination of seeds produced by plants grown at different CO(2) concentrations was significantly different. Female seeds from higher CO(2)-grown plants tended to emerge earlier than those from ambient-CO(2)-grown plants, but emergence of male seeds was little affected. Overall, seeds from elevated-CO(2)-grown plants had 20% higher germination and were more female-biased than those from ambient-CO(2)-grown plants. Because of the enhanced reproduction and more female-biased progeny under elevated CO(2), the population structure of this cosmopolitan weedy species will likely be altered in a future environment.