Elevated ozone reduced leaf nitrogen allocation to photosynthesis in poplar

Area of Science:

• Plant physiology
• Environmental science
• Biogeochemistry

Background:

• Leaf nitrogen (N) is crucial for photosynthesis.
• Ozone (O3) pollution impacts plant health and function.
• Understanding N allocation is key to predicting plant responses to environmental stress.

Purpose of the Study:

• Investigate elevated ozone's effects on leaf N concentration (mass-based and area-based).
• Analyze N allocation to leaf components under elevated O3.
• Determine the relationship between N and photosynthetic rates.

Main Methods:

• Two poplar clones were grown in open-top chambers with elevated O3.
• Leaf N concentration (Nmass, Narea), leaf mass per area (LMA), and N allocation were measured.
• Photosynthetic parameters were assessed in relation to leaf N.

Main Results:

• Elevated O3 increased Nmass but decreased Narea and LMA.
• A sensitive clone showed greater reductions in Narea and LMA.
• Narea positively correlated with photosynthetic rates (Asat).
• Elevated O3 reduced photosynthetic N-use efficiency (PNUE) and N allocation to photosynthetic components.
• N allocation to cell walls and other components increased under elevated O3.

Conclusions:

• Plants reallocate leaf N to cell walls and other components to cope with O3 stress, sacrificing photosynthetic N.
• Altered N allocation impacts plant physiology and may affect ecosystem processes like decomposition.