The rate of photosynthetic induction across different light intensities can be approximated using the light response curve of photosynthesis

While natural light in plant canopies often fluctuates and shows a large range of possible intensities, the rate of photosynthetic induction is often measured at only two light intensities. This prompts the question as to how the relationship between different light intensities and the rate of photosynthetic induction can be characterized. Using hundreds of measurements of photosynthetic induction at various light intensities in leaves of tomato (Solanum lycopersicum), we found linear relationships between the time to reach 50% of full photosynthetic induction (t50) and the difference between steady-state photosynthesis rates at low and at high light intensities (ΔA). This relationship was strongest at low leaf-to-air vapour pressure deficits (0.5-1.0 kilopascal), and when dark-adapted leaves were excluded. This relationship was documented at different CO2 mole fractions, namely 400 (R2 = 0.86), 600 (R2 = 0.66) and 800 µmol mol− 1 (R2 = 0.92). A survey of the literature suggested that this relationship also exists in various other tree and herbaceous species. The t50- ΔA relationship is particularly useful as proxy for the rate of photosynthetic induction between any two light intensities, through the use of conventional steady-state photosynthesis light response curves. A guide for best practice for characterizing the t50- ΔA relationship in the leaves of interest is provided.