Definitions of parameters: Average stomatal area: mean area of a guard cell pair, i.e. double ellipse 2*a*b*π, where a and b are the maximum length and maximum width of the guard cells (μm2). Leaf total stomatal area: the sum of all stomatal areas per leaf (μm2) Plant total stomatal area: the sum of all stomatal areas per plant (μm2) Plant total stomatal number: the sum number of all stomata per plant Minor vessel area: mean area of plant terminal vessels (μm2) Plant minor vessel number: the sum number of all terminal vessels per plant Stem xylem area: cross-sectional area of the entire xylem tissue in stems (μm2) Stem xylem conductance area: cross-sectional area of the conducting section in stem xylem (μm2) Average leaf area: mean area of single leaves (mm2) Total leaf area: the sum of all leaf areas per plant (mm2)