The response of photosystem I to fluctuating light is influenced by leaf nitrogen content in tomato

•We examine the effect of N supply on PSI performance under fluctuating light.•The redox state of PSI under FL is significantly affected by leaf N content.•The low PSII activity in LN-plants prevents PSI photoinhibition under FL.•The delayed CEF activation aggravates the over-reduction of PSI under FL.•Acceleration of CEF activation can alleviate PSI photoinhibition under FL.