Abstract: One of the main purposes of scientific research is to form questions and collect data to find patterns that best explain a particular process. In plant reproductive ecology, scientists have found important patterns including overwhelming occurrence of co-sexual flowers, separate flowering and fruiting periods, low seed-set ratio, simultaneous mass blooming, high occurrence of outcrossing in harsh habitats, interactions of mating systems and life-history, flower differentiations on the same inflorescence, and heteranthery (stamen differentiations in same flower). The underlying mechanisms of these patterns are in debate and are still in need of further examination. In this paper, we emphasize resource allocation at different levels, i.e. individual, inflorescence, and flower, and try to explain above patterns to reconcile some contradictory results obtained in studies based on different foci. Resource and sexual allocations directly determine the sexual role of a flower and floral traits, and as a consequence, plant mating systems are determined. In the future, studies considering both ecological factors and hierarchical levels will become more important and it is essential to focus more effort to study resource allocation to gain greater understanding and accurate predictions of floral adaptations and evolution.