An allometric framework is used to predict seed plant annual reproductive biomass based on standing leaf, stem, or root biomass. The scaling relations predicted by the resulting model are governed by manifold scaling exponents and taxon-specific constants reflecting the allometry of vegetative biomass partitioning patterns. The model accurately predicts all inter- and intraspecific reproductive biomass trends observed for a synoptic data base representative of herbaceous and arborescent dicot, monocot, and conifer species from diverse habitats. It also identifies the minimum body size below which reproduction is predicted to be energetically untenable. The limits for reproductive biomass among seed plants are thus established, providing a conceptual and quantitative basis for understanding the scaling of sexual reproduction across and within ecologically and evolutionarily diverse seed plants.

Key words: allometry, biomass, reproduction, seed plants