The effects of density on size-dependent gender plasticity in the monoecious species Sagittaria potamogetifolia (Alismataceae)

Abstract

Aim To test the fitness-gain curve model proposes that cosexual plants adjust their sex ratios and resource allocation depending on their size. In this study, the monoecious species Sagittaria potamogetifolia was used as a model to determine the effects of plant size and density on gender modification and reproductive allocation. Methods and materials Various traits, including flower number and plant biomass, were measured under four different artificially constructed population density treatments. More male flowers were produced than female flowers per individual at high densities, while the opposite trend was observed at low densities. This trend was particularly evident in the highest density treatment. Results A trade-off was discovered between male–female sex allocations in the highest density treatment (40 individuals m−2). The allometric growth of reproductive organs compared with plant size was detected, as evidenced by the reproductive structures’ biomass and flower numbers. However, in the highest density treatment, size was weakly negatively correlated with femaleness. Conclusion Thus, S. potamogetifolia has a reproductive strategy that easily adjusts to different reproductive environmental densities.