Exploring prediction mechanisms for temperature-induced variation in maximum carboxylation rate from spectral reflectance across 450-850 nm in cucumber leaves

Leaf spectral reflectance across 450-850 nm has been shown to predict maximum carboxylation rate (Vcmax), which varies with leaf temperature (Tleaf). However, the mechanism by which temperature-induced variation in Vcmax is predicted from reflectance remains unclear. The objective of this study was to explore this mechanism using spectral reflectance across 450-850 nm. We measured Vcmax across a range of Tleaf (18-31C) and reflectance in cucumber (Cucumis sativus L.) leaves. Partial least squares regression models moderately predicted Vcmax (R² = 0.73), whereas Tleaf was weakly predicted (R² = 0.32). When only visible reflectance (450-700 nm) was used, prediction accuracy for both Vcmax and Tleaf declined (R² = 0.59 and 0.17). Because predicting Tleaf from reflectance suggests that temperature-related information may help predict temperature-induced variations in Vcmax, our results indicate that reflectance in 700-850 nm possibly captures temperature-induced variation in Vcmax.