Optimal leaf life strategies determine V c,max dynamic during ontogeny

• Leaf photosynthetic properties, for example the maximum carboxylation velocity or V c,max, change with leaf age due to ontogenetic processes. This study introduces an optimal dynamic allocation scheme to model changes in leaf-level photosynthetic capacity as a function of leaf biochemical constraints (costs of synthesis and defence), nitrogen availability and other environmental factors (e.g. light). • The model consists of a system of equations describing RuBisCO synthesis and degradation within chloroplasts, defence and ageing at leaf levels, nitrogen transfer and carbon budget at plant levels. • Model results show that optimal allocation principles explained RuBisCO dynamics with leaf age. An approximated analytical solution can reproduce the basic pattern of RuBisCO and V c,max in rice and in two tropical tree species. The model also reveals leaf life complementarities that remained unexplained in previous approaches, as the interplay between V c,max at maturation, life span and the decline in photosynthetic capacity with age. Furthermore, it explores the role of defence, which is not implemented in current models. • This framework covers some of the existing gaps in integrating multiple processes across plant organs (chloroplast, leaf and whole plant) and is a first-step towards representing mechanistically leaf ontogenetic processes into physiological and ecosystem models.