Optimal leaf life strategies determine V_c,max dynamic during ontogeny.

Area of Science:

• Plant Physiology
• Ecology
• Biochemistry

Background:

• Leaf photosynthetic capacity, including maximum carboxylation velocity (Vc,max), changes with leaf age due to ontogenetic processes.
• Existing models often lack integration of biochemical constraints, nitrogen availability, and environmental factors in leaf development.

Purpose of the Study:

• To introduce an optimal dynamic allocation scheme to model changes in leaf-level photosynthetic capacity.
• To investigate the influence of biochemical constraints, nitrogen, and environmental factors on photosynthetic capacity.
• To explore leaf life complementarities and the role of defence in leaf ontogeny.

Main Methods:

• Developed a model comprising equations for RuBisCO synthesis/degradation, defence, ageing, nitrogen transfer, and carbon budget.
• Applied optimal allocation principles to simulate changes in photosynthetic capacity.
• Used an approximated analytical solution to validate model predictions against data from rice and tropical tree species.

Main Results:

• Optimal allocation principles successfully explained RuBisCO dynamics across leaf age.
• The model reproduced the basic patterns of RuBisCO and Vc,max in different plant species.
• Identified previously unexplained leaf life complementarities, including the interplay between Vc,max, lifespan, and age-related photosynthetic decline.

Conclusions:

• The developed framework mechanistically integrates multiple processes across plant organs (chloroplast, leaf, whole plant).
• This study provides a first step towards incorporating leaf ontogenetic processes into physiological and ecosystem models.
• The model highlights the significance of defence mechanisms in leaf development and function.