Simultaneous 3/4‐power scaling of leaf mass and 2/3‐power scaling of leaf area with stem mass in plants

Background: Plant allometry theory developed last century focused on 2/3-power scaling, determined by light interception considerations. More recently 3/4-power scaling based on the properties of vascular distribution networks has been proposed. Methods: We assembled 783 observations on plant height, leaf area, leaf mass, stem mass and total mass, for eight species groups and spanning eight orders of magnitude for total mass to empirically explore which scaling theory best defines plant allometry. Results: The data confirmed that the relationship between leaf mass and stem mass follows ¾-power scaling. However, leaf area–total (leaf plus stem) mass relationships follow 2/3-power scaling. Previously reported non-1:1 scaling of leaf area:total mass and associated lower specific leaf area of larger plants emerges as a mechanism whereby 3/4-power scaling of organ mass for resource distribution and 2/3-power scaling of leaf area for light capture are reconciled in one body plan. In our data set, scaling coefficients of leaf area:total mass in smaller plants tend towards 1:1, which is intuitively logical where stems provide only leaf–root connection without leaf support for light capture. Conclusions: A unified theory of plant allometry would integrate ¾-power scaling of organ mass for resource distribution, 2/3-power scaling of leaf area for light capture, scaling near 1:1 for small plants and provision for variation reflecting species-specific body plan configuration.