Fig. 7. Efficiency of biosynthesis of fractions of lignins associated with the three main monolignol residues containing nine (hydroxyphenol), 10 (guaiacyl) or 11 (syringyl) carbon atoms per residue when the most efficient reaction sets of biosynthesis were used. Efficiency was quantified by the retention of carbon (solid lines) and energy (dashed lines) in lignin per unit carbon (or energy) contained in the sucrose substrate of lignin biosynthesis (Table 7) (reaction sets including methanol as cosubstrate were not considered here). Energy retention was larger than carbon retention because lignins are more reduced (more energy per carbon atom) than sucrose. All calculations were based on Y_ATP,sucrose = 60 ATP per sucrose, Y_{ATP,cyt‐NADH} = 1·5 ATP formed per NADH oxidized, and Y_{ATP,cyt‐NADPH} = 1·5 ATP formed per NADPH oxidized.