where c is a scaling constant, Ha (kJ mol−1), is the activation energy and R is the universal gas constant. The scaling constant (c) values are 35.98, 12.37 and 11.18 for Kc, Ko and Γ*, respectively. The values of Ha are 80.99, 23.72 and 24.46 for Kc, Ko and Γ*, respectively (Sharkey et al., 2007).