Wind and gravity mechanical effects on leaf inclination angles

• A biomechanical model of Leaf Inclination Angle Distribution (LIAD) is proposed.
• Self-weight and wind loading are considered.
• Leaf flexibility impacts strongly Leaf Inclination Angle Distribution.
• A change in leaf flexibility or external loading may change light interception.

In a tree, the distribution of leaf inclination angles plays an important role in photosynthesis and water interception. We investigate here the effect of mechanical deformations of leaves due to wind or their own weight on this distribution. First, the specific role of the geometry of the tree is identified and shown to be weak, using models of idealized tree and tools of statistical mechanics. Then the deformation of individual leaves under gravity or wind is quantified experimentally. New dimensionless parameters are proposed, and used in simple models of these deformations. By combining models of tree geometry and models of leaf deformation, we explore the role of all mechanical parameters on the Leaf Inclination Angle Distributions. These are found to have a significant influence, which is exemplified finally in computations of direct light interception by idealized trees.