The Inverse Relationship Between Solar-Induced Fluorescence Yield And Photosynthetic Capacity: Benefits For Field Phenotyping

Improving photosynthesis is considered a promising way to increase crop yield to feed a growing population. Realizing this goal requires non-destructive techniques to quantify photosynthetic variation among crop cultivars. Despite existing remote sensing-based approaches, it remains a question whether solar-induced fluorescence (SIF) can facilitate screening crop cultivars of improved photosynthetic capacity in plant breeding trials. Here we tested a hypothesis that SIF yield rather than SIF had a better relationship with the maximum electron transport rate (J(max)). Time-synchronized hyperspectral images and irradiance spectra of sunlight under clear-sky conditions were combined to estimate SIF and SIF yield, which were then correlated with ground-truth V-cmax and J(max). With observations binned over time (i.e. group 1: 6, 7, and 12 July 2017; group 2: 31 July and 18 August 2017; and group 3: 24 and 25 July 2018), SIF yield showed a stronger negative relationship, compared with SIF, with photosynthetic variables. Using SIF yield for J(max) (V-cmax) predictions, the regression analysis exhibited an R-2 of 0.62 (0.71) and root mean square error (RMSE) of 11.88 (46.86) mu mol m(-2) s(-1) for group 1, an R-2 of 0.85 (0.72) and RMSE of 13.51 (49.32) mu mol m(-2) s(-1) for group 2, and an R-2 of 0.92 (0.87) and RMSE of 15.23 (30.29) mu mol m(-2) s(-1) for group 3. The combined use of hyperspectral images and irradiance measurements provides an alternative yet promising approach to characterization of photosynthetic parameters at plot level.