Table 1.

Coefficient of determination (R²) from simple linear regression models evaluating the bivariate relationship between each environmental predictor and quantum yield of photosystem II (Φ_PSII).

Predictors	R2
ePPFD15	0.525
ePPFDi	0.488
PPFD15	0.417
PPFDi	0.406
CO2	0.163
Temp	0.0812
VPD	0.0435
eDLI_cum	0.0348
DLI_cum	0.0184

Each model was fitted independently using the full dataset without any data splitting or cross-validation.

Where: ePPFD15, 15-min average extended photosynthetic photon flux density (400–750 nm); ePPFDi, instantaneous ePPFD; PPFD15, 15-min average PPFD (400–700 nm); PPFDi, instantaneous PPFD; CO₂, carbon dioxide concentration; Temp, air temperature; VPD, vapor pressure deficit; eDLI_cum, extended daily light integral accumulated from dawn to time of measurement (400–750 nm); and DLI_cum, daily light integral accumulated from dawn to time of measurement (400–700 nm).