Table 2.
Regression coefficients for the multiple linear regression model used to predict the quantum yield of photosystem II (ΦPSII).
| Predictors | Coefficients | Standard errors | P-values |
|---|---|---|---|
| Intercept | 5.30 × 10-1 | 3.26 × 10-2 | < 0.001 |
| ePPFD15 | -1.62 × 10-4 | 8.25 × 10-6 | < 0.001 |
| ePPFDi | -9.45 × 10-5 | 6.97 × 10-6 | < 0.001 |
| Temp | -3.80 × 10-3 | 7.66 × 10-4 | < 0.001 |
| VPD | 5.03 × 10-2 | 4.08 × 10-3 | < 0.001 |
| CO2 | 5.71 × 10-4 | 5.82 × 10-5 | < 0.001 |
| Time-of-day1 | 5.80 × 10-3 | 3.72 × 10-3 | 0.119 |
Predictors included 15-min averaged and instantaneous extended photosynthetic photon flux density (ePPFD15 and ePPFDi), air temperature (Temp), vapor pressure deficit (VPD), carbon dioxide concentration (CO2), and Time-of-day.
¹Time-of-day was included as a binary categorical variable coded as “afternoon” (reference) and “beforenoon” (estimate shown). The positive coefficient indicates that ΦPSII tended to be higher in the beforenoon compared to the afternoon.