Sexual dimorphism in leaf nitrogen content but not photosynthetic rates in Sagittaria latifolia (Alismataceae)

摘要

Sexual dimorphism in reproductive costs between females and males in dioecious plants is associated with divergent morphologies, life histories, and physiologies between the sexes. In Sagittaria latifolia Willd. (Alismataceae), a previous experiment has shown that sexual reproduction imposes asymmetric costs for females vs. males, with greater biomass costs for females and greater nitrogen costs for males. Here we investigate whether sexual dimorphism in nitrogen expenditure for reproduction influences the nitrogen content of leaves under natural conditions and, if so, whether it is associated with differences in photosynthetic rates between the sexes. As expected, we found significantly lower leaf nitrogen content among males compared with females and a positive association between leaf nitrogen content and photosynthetic rates. However, this difference in nitrogen content between the sexes was not associated with different photosynthetic rates for females vs. males. Our study demonstrates that an underlying difference in nitrogen content between the sexes is maintained during flower and fruit production in a natural population, but, at least at the site used for this study, this difference was not associated with divergent photosynthetic rates.