## 5 Conclusions  
In this study, we explored the response of \(\mathrm{SIF}_{canopy}\) to APAR\({}_{chl}\) for both the O\({}_{2}\)-A and O\({}_{2}\)-B bands using both a simulation carried out by the SCOPE model and also field observations. The results showed that, at both these bands, \(\mathrm{SIF}_{canopy}\) had a strong linear relationship with APAR\({}_{chl}\) for a canopy with a constant LAI and Cab content. At the O\({}_{2}\)-A band, compared to the O\({}_{2}\)-B band, the relationship between \(\mathrm{SIF}_{canopy}\) and APAR\({}_{chl}\) is relatively insensitive to the LAI and Cab content based on the simulated dataset, which are primarily determined by the specific vegetation structure. In contrast, the response of \(\mathrm{SIF}_{canopy}\) to APAR\({}_{chl}\) at the O\({}_{2}\)-B band is very sensitive to the LAI and Cab content even for canopies with the same structure (the same LAD in the simulation experiment). This confirms that, at the O\({}_{2}\)-B band, due to reabsorption effects, \(\mathrm{SIF}_{canopy}\) is more influenced by the biochemical components of the canopy. The ratio of \(\mathrm{SIF}_{canopy}\) to APAR\({}_{chl}\) was also analyzed for different concentrations of biochemical components and canopy structures and it was found that the influence of these factors is greater at the O\({}_{2}\)-B band than it at the O\({}_{2}\)-A band. As Cab increases, the ratio of \(\mathrm{SIF}_{canopy}\) to APAR\({}_{chl}\) ranges from 0.016 to 0.002 \(\mathrm{\SIUnitSymbolMicro m}^{-1}\) sr\({}^{-1}\) for the O\({}_{2}\)-B band but remains almost invariant at the O\({}_{2}\)-A band for a given LAI. Similarly, based on the field experiments, the effect of different fertilization treatments and varieties on the relationship between \(\mathrm{SIF}_{canopy}\) and APAR\({}_{chl}\) is negligible. The relationship between \(\mathrm{SIF}_{canopy}\) and APAR\({}_{chl}\) is also not significantly affected by Cab content and \(f_{c}\) at O\({}_{2}\)-A band compared to O\({}_{2}\)-B band. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{5}{c}{**Field Experiment Dataset**} \\ \hline  & **XTS Farm** & **Sanya Station** & **Nanbin Farm** & **All** \\ \hline  & y = 0.0050x + 0.0261 & y = 0.0065x + 0.1220 & y = 0.0134x \(-\) 0.3721 & y = 0.0062x + 0.0240 \\ O\({}_{2}\)-A & R\({}^{2}\) = 0.9150, & R\({}^{2}\) = 0.7870, & R\({}^{2}\) = 0.8390, & R\({}^{2}\) = 0.6551, \\ band & RMSE = 0.0820 & RMSE = 0.1540 & RMSE = 0.2030 & RMSE = 0.2070 \\  & y = 0.0052x & y = 0.0076x & y = 0.0092x & y = 0.0064x \\  & (2\(\sigma\) = 0.0004) & (2\(\sigma\) = 0.0036) & (2\(\sigma\) = 0.0020) & y = 0.0064x \\ \hline  & y = 0.0032x + 0.0095 & y = 0.0035x + 0.1650 & y = 0.0034x + 0.2559 & y = 0.0032x + 0.1103 \\ O\({}_{2}\)-B & R\({}^{2}\) = 0.8190, & R\({}^{2}\) = 0.7070 & R\({}^{2}\) = 0.3360, & R\({}^{2}\) = 0.5192, \\ band & RMSE = 0.0830 & RMSE = 0.0900 & RMSE = 0.1670 & R\({}^{2}\) = 0.1500 \\  & y = 0.0033x & y = 0.0049x & y = 0.0063x & r\({}^{2}\) = 0.0041x \\  & (2\(\sigma\) = 0.0004) & (2\(\sigma\) = 0.0030) & (2\(\sigma\) = 0.0014) & y = 0.0041x \\ \hline  & \multicolumn{5}{c}{**Simulated Dataset**} \\ \hline  & \multicolumn{2}{c}{**Erectophile**} & **Spherical** & **Planophile** \\ \hline  & y = 0.0035x \(-\) 0.0763 & y = 0.0057x \(-\) 0.0372 & y = 0.0067x + 0.0321 \\ O\({}_{2}\)-A & R\({}^{2}\) = 0.9940, RMSE = 0.0170 & R\({}^{2}\) = 0.9992, RMSE = 0.0120 & R\({}^{2}\) = 0.9998, RMSE = 0.0160 \\ band & y = 0.0031x & y = 0.0055x & y = 0.0068x \\  & (2\(\sigma\) = 0.0002) & (2\(\sigma\) = 0.0002) & (2\(\sigma\) = 0.0001) \\ \hline  & y = 0.0017x \(-\) 0.0598 & y = 0.0034x \(-\) 0.0506 & y = 0.0046x + 0.0232 \\ O\({}_{2}\)-B & R The effect of LAD on the relationship between \(\text{SIF}_{canopy}\) and \(\text{APAR}_{chl}\) was also investigated using both simulations and field observations. The relationship between \(\text{SIF}_{canopy}\) and \(\text{APAR}_{chl}\) varies for different LAD functions and the slope of the graph of \(\text{SIF}_{canopy}\) against \(\text{APAR}_{chl}\) decreases for a more erect canopy.