SIF760 tracks the diurnal variations in GPP over C3/C4 crop canopies well. SIF760 is linearly correlated with GPP for C3 and C4 crops at the diurnal scale. The slope of the GPP–SIF760 relationship is higher for C4 crops. The large difference in εP between C3 and C4 crops determines the difference in the slope εPεF. The photosynthetic type should be considered when discussing the GPP–SIF relationship.