A physical interpretation for the natural photosynthetic process.

The efficiency of the process of photosynthesis is shown to depend on the molecular conversion of power. This requires establishment of a discipline that is now implicit in current thought and that offers a definition of relationship between equilibrium state and power. The quantum aspect for the microscopic process is different from the macroscopic system idealized as the heat engine and is required for the interpretation of molecular machinery. By using three postulates the ideal maximal efficiency for the molecular energy conversion is calculated from the data, which are assembled in the form of the "Z scheme" for photosynthesis. The observed and the calculated efficiencies for a green plant are substantially in agreement.