Petiole–lamina coordination reveals adaptive trade-offs across environmental gradients

Plant ecological strategies fundamentally rely on the coordinated investment between photosynthetic and structural organs. Yet, the petiole—a pivotal connector mediating mechanical support, hydraulic transport, and light interception—has long been marginalized in trait-based ecological frameworks. Despite its small size, the petiole determines how leaves are positioned in space, how efficiently water and carbon are exchanged, and how mechanical stresses are distributed across the canopy. Neglecting this structure limits our understanding of how plants integrate form and function to adapt to environmental variability.

To address this gap, we compiled global and regional datasets encompassing more than hundreds of woody angiosperm species and a comprehensive suite of petiole and lamina traits. Combining multivariate trait analyses, scaling theory, and environmental modeling, we examined how the coordination between petiole and lamina traits reflects adaptive trade-offs across climatic gradients. Along a 4,000-km latitudinal transect in China, we show that petiole traits define a distinct two-dimensional functional space structured by orthogonal axes of mechanical support and hydraulic efficiency. This functional space operates largely independently from the classical leaf economics spectrum, thereby expanding the current conceptual framework of plant functional diversity.

We further found that the strength of allometric scaling between lamina and petiole traits declines toward higher latitudes, indicating reduced structural coupling under low-energy conditions. In contrast, associations between petiole traits and leaf geometric attributes—such as centroid ratio and length-to-width ratio—reveal new dimensions of functional integration linking leaf form to biomechanical stability and resource-use efficiency. These patterns highlight the central role of the petiole as both a mechanical and hydraulic mediator in the evolution of plant form.

Collectively, our results demonstrate that petiole traits are not passive extensions of the lamina but key regulators of aboveground function and adaptation. Integrating the lamina–petiole complex into trait-based frameworks provides a more holistic understanding of how plants balance mechanical safety, hydraulic efficiency, and light capture across environmental gradients, refining predictions of vegetation responses to global environmental change.