• carbon gain;
  • leaf hydraulic conductance;
  • leaf lifespan;
  • leaf size;
  • photosynthesis;
  • water transport


  • Previous research suggests that the lifetime carbon gain of a leaf is constrained by a tradeoff between metabolism and longevity. The biophysical reasons underlying this tradeoff are not fully understood.
  • We used a photosynthesis–leaf water balance model to evaluate biophysical constraints on carbon gain. Leaf hydraulic conductance (KLeaf), carbon isotope discrimination (Δ13C), leaf mass per unit area (LMA) and the driving force for water transport from stem to leaf (ΔΨStem–Leaf) were characterized for leaves spanning three orders of magnitude in surface area and two orders of magnitude in lifespan.
  • We observed positive isometric scaling between KLeaf and leaf area but no relationship between Δ13C and leaf area. Leaf lifespan and LMA had minimal effect on KLeaf per unit leaf area, but a negative correlation exists among LMA, lifespan, and KLeaf per unit dry mass. During periods of leaf water loss, ΔΨStem–Leaf was relatively constant.
  • We show for the first time that KLeaf, mass, an index of the carbon cost associated with water use, is negatively correlated with lifespan. This highlights the importance of characterizing KLeaf, mass and suggests a tradeoff between resource investment in liquid phase processes and structural rigidity.