RODERICK C. DEWAR
The Correlation between Plant Growth and Intercepted Radiation: An Interpretation in Terms of Optimal Plant Nitrogen Content
Annals of Botany : Volume 78, Issue 1, July 1996, Pages 125-136 pdf
Photosynthesis of leaves is commonly observed to have a saturating response to increases in their nitrogen (N) content, while the response of plant maintenance respiration is more nearly linear over the normal range of tissue N contents. Hence, for a given amount of foliage, net primary productivity (NPP) may have a maximum value with respect to variations in plant N content. Using a simple analytically-solvable model ofNPP, this idea is formulated and its broad implications for plant growth are explored at the scale of a closed stand of vegetation. The maximum-NPPhypothesis implies thatNPPis proportional to intercepted radiation, as commonly observed. The light utilization coefficient (ε), defined as the slope of this relationship, is predicted to be
where α is the quantum yield,Ygis the biosynthetic efficiency, and λ is a dimensionless combination of physiological and environmental parameters of the model. The maximum-NPPhypothesis is also consistent with observations that whole-plant respiration (R) is an approximately constant proportion of gross canopy photosynthesis (Ac), and predicts their ratio to be
Using realistic parameter values, predicted values for ε andR:Acare typical of C3plants. ε is predicted to be independent of plant N supply, consistent with observations that long-term growth responses to N fertilization are dominated by increased light interception associated with increased growth allocation to leaf area. Observed acclimated responses of plants to atmospheric [CO2], light and temperature are interpreted in terms of the model.