Cell wall thickness has phylogenetically consistent effects on photosynthetic nitrogen-use efficiency of terrestrial plants: a meta-analysis

Leaf photosynthetic nitrogen-use efficiency (PNUE) diversified significantly among C 3 species. However, morpho-physiological mechanisms and interrelationships forming PNUE remain unclear on the evolutionary time scale. In this study, we compiled a novel extensive matrix of morpho-anatomical and physiological traits of leaf in 679 C 3 species ranging from bryophytes to angiosperms to understand the intricacy of interrelationships underlying the variations in PNUE. We found that LMA, mesophyll cell wall thickness (T cwm ), Rubisco N allocation fraction (P R ), and mesophyll conductance (g m ) together interpreted 83% of variations in PNUE, with P R and g m accounting for 65% of those variations. However, the P R effects were species-dependent on g m ; that is, the contribution of P R on PNUE was extensively significant in high-g m species in comparison to low-g m species. Standard major analysis (SMA) and path analysis suggested a weak correlation between PNUE and LMA, whereas the SMA correlation for PNUE–T cwm was strong. The P R was inversely proportional to T cwm , which was similar to the relationship between g m and T cwm (p-value < 0.01), so that the internal CO 2 drawdown from intercellular airspace to carboxylaton sites was relatively conservative over a wide range of T cwm . Collectively, the coordination of changes in P R and g m connecting T cwm suggested the complex physiological mechanisms mediated by T cwm modulating PNUE across contrasting plant groups.