The Effects of Varying Nutrient Availability on Females and Hermaphrodites of the Gynodioecious Geranium maculatum

ABSTRACT Sexual dimorphism in plant growth and/or reproductive responses to the surrounding environment has been documented in some plant species. In gynodioecious plants, it is especially important to understand whether females and hermaphrodites differ in their response to environmental stressors, as the fitness of females relative to hermaphrodites determines the extent to which these separate sexes are maintained in natural populations. Soil nutrient availability is of particular importance given the different nutrient requirements of male and female sexual functions in plants. Here, we evaluated and compared the growth of females and hermaphrodites of Geranium maculatum in response to varying levels of nutrients. Using a greenhouse experiment, we manipulated the overall nutrient, nitrogen, and phosphorus levels in the soil and measured growth, allocation, and leaf quality responses in both females and hermaphrodites. We found that the sexes responded similarly in their growth and allocation responses to nutrient availability, despite evidence that female leaf chlorophyll content may have increased more than that of hermaphrodites across soil nitrogen levels. Our findings demonstrate that while hermaphrodites may differ from females in terms of their physiological response to varying nutrient levels, these slight physiological differences do not translate into meaningful growth differences.