Effect of nitric oxide on leaf non-photochemical quenching of fluorescence under heat-stress conditions

Non-photochemical quenching (NPQ) is a photoprotection mechanism in photosynthesis that can be monitored by NPQ of chlorophyll a fluorescence. Comparing NPQ response of Arabidopsis thaliana intact leaves between the wild type and ΔGLB3, which lacks truncated hemoglobin gene, we report here the effects of nitric oxide (NO) on NPQ under stress conditions. Heat stress was found to severely decline NPQ of ΔGLB3. The effect was mimicked by chemical NO donors, and it was completely prevented by the NO scavenger cPTIO. These results suggest that NO is involved in the decline of NPQ which is pronounced under heat stress conditions.