SPECTROPHOTOMETRIC ANALYSIS OF NECTAR PRODUCTION IN SILENE VULGARIS (CARYOPHYLLACEAE)

Significant differences in nectar content were observed between hermap hrodite and female plants of the gynomonoecious-gynodioecious taxon, S ilene vulgaris, from populations in northern lower Michigan. These dif ferences in nectar sugar content were observable with a carbohydrate d igestion technique involving sulfuric acid, phenol, and measurement of the color change with a spectrophotometer. A hand-held refractometer did not provide sufficient resolution to discern differences between t he genders. Both genders were similar in the pattern of sugar content of nectar during floral development. A split-plot factorial design rev ealed significant differences both among individual plants and stages of floral phenology within each gender. The spectrophotometric techniq ue and statistical analysis provided the needed resolution to discern differences between the genders that we relate to pollinator activity, levels of inbreeding depression, and the maintenance of gynodioecy in this taxon.