Fig. 1.

High light–induced changes in photochemical responses and metabolite abundances in Arabidopsis. Arabidopsis in a growth chamber (Fig. 3A) were dark adapted for at least 20 min before being exposed to 100 and 500 μmol protons m⁻²·S⁻¹ LED light. Chlorophyll fluorescence measurements were transformed to three parameters that describe the fate of excitation energy in PSII, including Y(II)-quantum yields of photochemical energy conversion in PSII (A), Y(NPQ)-quantum yields of regulated nonphotochemical energy loss in PSII (B), and Y(NO)-quantum yields of nonregulated nonphotochemical energy loss in PSII (C). Arabidopsis plants were exposed to 100 and 500 μmol protons m⁻²·S⁻¹ LED light for 1, 2, 5, and 8 h before their Fv/Fm values were determined by maxi-PAM (D). Specific amino acids (triple quadrupole mass spectrometry, QQQ) and organic acids (quadrupole time-of-flight mass spectrometry, Q-TOF) that increased in abundance in response to high light treatment (E). Error bars show SDs for photochemical parameter measurements (biological replicates n = 4) and SEs for metabolite measurements (biological replicates n = 3). Statistical significance tests were performed with a Student’s t test (**P < 0.01, *P < 0.05).