where K(Tk) is the Vcmax or Jmax at temperature Tk which is the leaf temperature in Kelvin, K25 is the value of Vcmax or Jmax at Tref = 25 °C, R is the universal gas constant (8.314 J mol−1 K−1), Ha (kJ mol−1) is the activation energy, Hd (kJ mol−1) is the energy of deactivation and ΔS (J mol−1) is an entropy term.