Leaf Nitrogen Content and CO2 Assimilation Capacity in Peach1

Differences in the photosynthetic capacity of leaves of peach [ Prunus persica (L.) Batsch cv. Golden Glory] were investigated in conjunction with their leaf nitrogen and phosphorus content. Photosynthetic CO 2 assimilation expressed on a leaf area basis, mesophyll conductance, and leaf conductance to water vapor were all linearly related to leaf nitrogen content expressed on a leaf area basis (R 2 = 0.908, 0.921, 0.685, respectively). Leaf intercellular CO 2 concentrations tended to decrease slightly with increasing CO 2 assimilation rates and leaf N contents, indicating that CO 2 assimilation was not being restricted by low intercellular CO 2 concentrations and leaf conductances in leaves with lower assimilation capacity. CO 2 assimilation, mesophyll conductance, and leaf conductance to water vapor were also linearly related to leaf phosphorus content, but these relationships were not as clear as for leaf nitrogen content. (R 2 = 0.601, 0.687, 0.324, respectively). The maximum CO 2 assimilation rate per unit of leaf nitrogen for peach leaves in this experiment was between 6.0 and 7.0 nmol CO 2 mg N −1 s −1 .