Linking photosynthesis and leaf N allocation under future elevated CO2 and climate warming in Eucalyptus globulus.

Area of Science:

• Plant Physiology
• Biochemistry
• Climate Change Biology

Background:

• Accurate estimation of atmospheric CO2 uptake relies on leaf-level photosynthetic models.
• These models require precise Rubisco kinetics, a crucial enzyme in carbon fixation.

Purpose of the Study:

• To investigate the impact of canopy position, elevated CO2 (eC), and elevated temperature (eT) on Rubisco content and activity in Eucalyptus globulus.
• To determine the relationship between leaf nitrogen (N) and Vcmax (maximal Rubisco carboxylation rate) under these conditions.

Main Methods:

• Studied 7m tall, soil-grown Eucalyptus globulus trees.
• Assessed Rubisco content, activity, and kinetics under ambient and elevated CO2 and temperature treatments.
• Analyzed leaf N and Vcmax relationships.

Main Results:

• Eucalyptus Rubisco kinetics are similar to tobacco and consistent with in vitro Vcmax estimates.
• The fraction of leaf nitrogen invested in Rubisco was lower than in crop species and varied with treatments.
• Photosynthetic acclimation to eC involved reduced leaf N and Rubisco; eT led to increased Rubisco content and growth resumption.

Conclusions:

• Eucalyptus globulus exhibits significant adaptive capacity in nitrogen allocation to Rubisco and other photosynthetic proteins.
• Flexible allocation optimizes photosynthesis in response to future climate scenarios with elevated CO2 and temperatures.
• Findings are crucial for refining models of forest carbon uptake in a changing climate.