## 2 Materials and Methods
### Experiment Design  
This section outlines the protocol for measuring response curves under varying environmental conditions (light, CO\({}_{2}\), and temperature) using the developed system. Prior to the measurements, the target leaf was fully dark-adapted and positioned in the chamber under dark conditions, with its adaxial surface facing the light source, ensuring full coverage of the chamber. The initial chamber conditions were set as follows: light intensity of 0 \(\upmu\)mol m\({}^{-2}\) s\({}^{-1}\), air flow rate of 500 \(\upmu\)mol s\({}^{-1}\), CO\({}_{2}\) concentration of 420 \(\upmu\)mol mol\({}^{-1}\), leaf temperature of 25 \({}^{\circ}\)C, and relative humidity of 50%. Measurements of minimum (F\({}_{o}\)) and maximum fluorescence in the dark-adapted state (F\({}_{m}\)), along with dark respiration (\(R_{d}\), \(\upmu\)mol m\({}^{-2}\) s\({}^{-1}\)), were taken before increasing the light intensity. The light response curve was subsequently recorded at light intensities of 30, 50, 100, 200, 400, 600, 900, 1200, 1500, 1800, and 2100 \(\upmu\)mol m\({}^{-2}\) s\({}^{-1}\). At each intensity, a stabilization period of 5-20 min was allowed for the gas exchange to reach a steady state. Following stabilization, measurements  
Figure 2: Calibration procedures for the developed system. (**a**) Schematic representation of the calibration process. (**b**) Laboratory setup during system calibration. (**c**) Calibration factors calculated for a spectrometer at different integration times. (**d**) Calibration factors normalized to integration time. of net photosynthesis (\(A_{\text{net}}\), \(\mu\)mol m\({}^{-2}\) s\({}^{-1}\)), steady-state fluorescence (F\({}_{\text{s}}\)), and minimum (F\({}_{\text{o}}\)') and maximum fluorescence in the light-adapted state (F\({}_{\text{m}}\)') were recorded, along with \(Rad_{\text{UP}}\), \(Rad_{\text{DOWN}}\), ChFl\({}_{\text{UP}}\), and ChFl\({}_{\text{DOWN}}\) corresponding to F\({}_{\text{s}}\). The light intensity was then adjusted to the next level, and the procedure was repeated until the full light response curve was obtained. After completing the light response curve measurements, the CO\({}_{2}\) response curve was recorded at a saturated light intensity of 1500 \(\mu\)mol m\({}^{-2}\) s\({}^{-1}\) using a series of CO\({}_{2}\) concentrations: 420, 30, 50, 100, 200, 300, 400, 600, 900, 1200, and 1500 \(\mu\)mol mol\({}^{-1}\). A stabilization period of 5-20 min was allowed at each concentration before recording the data, following the same protocol as for the light response curve. The temperature response curve was then measured while maintaining a constant light intensity of 1500 \(\mu\)mol m\({}^{-2}\) s\({}^{-1}\) and a CO\({}_{2}\) concentration of 420 \(\mu\)mol mol\({}^{-1}\). The leaf temperature was sequentially adjusted to 25, 15, 20, 25, 30, 35, 40, and 45 \({}^{\circ}\)C. In the same way as for the other response curves, the gas exchange was allowed to stabilize for 5-20 min before the data collection for each temperature. Note that throughout all the measurements, the leaf remained fixed in its position within the chamber to ensure consistency. After completing the environmental response curve measurements, reflectance and transmittance spectra (hereafter referred to as \(\rho\) and \(\tau\)) across the wavelength range of 350-2500 nm were measured on the same leaf using a Fluowat leaf clip and a spectrometer (PSR+ 3500; Spectral Evolution, MA, USA; 1 nm spectral resolution, 350-2500 nm). The radiation characteristics of the light source were also evaluated using a standard reflectance panel (Guangzhou Jingyi Photoelectric Technology Co., Ltd., Guangzhou, China; \(\sim\)2% reflectance). In this study, we conducted concurrent measurements of leaf gas exchange and actively and passively induced chlorophyll fluorescence across 52 species representing major plant functional types (Table S1).