Leaf structural responses to pre-industrial, current and elevated atmospheric [CO₂] and temperature affect leaf...

Area of Science:

• Plant physiology
• Climate change biology
• Eucalyptus ecophysiology

Background:

• Leaf structure and chemistry critically regulate photosynthesis.
• The impact of changing leaf structure on photosynthesis under elevated atmospheric CO2 (CO2) and temperature remains unclear.
• Understanding these responses is vital for climate change research.

Purpose of the Study:

• To investigate the interactive effects of elevated CO2 and temperature on leaf structural and chemical traits influencing photosynthesis.
• To identify key leaf traits regulating photosynthetic responses to environmental changes in Eucalyptus sideroxylon.

Main Methods:

• Experimental manipulation of atmospheric CO2 concentrations (290, 400, 650 μLL-1) and temperature (ambient, ambient +4°C).
• Measurement of leaf structural (e.g., palisade layers, stomatal frequency) and chemical traits (e.g., leaf nitrogen per area).
• Assessment of photosynthetic rates (light-saturated net photosynthetic rates and maximum photosynthetic capacity).

Main Results:

• Increased atmospheric CO2 enhanced light-saturated net photosynthetic rates but reduced photosynthetic capacity.
• Leaf nitrogen per unit area and palisade layer number were significant predictors of photosynthetic capacity variation under rising CO2.
• Elevated temperature increased stomatal frequency but did not significantly alter photosynthetic capacity; interactive effects of CO2 and temperature were minimal.

Conclusions:

• Leaf nitrogen content and palisade layer structure are key regulators of Eucalyptus sideroxylon photosynthetic capacity under elevated CO2.
• Limited impact of elevated temperature on photosynthesis may be due to its minimal effects on leaf structure and chemistry.
• Leaf structural and chemical adjustments are crucial for predicting plant responses to future climate conditions.