Two days at 38/29 C and optimum light (HT-NL) resulted in reduction of NPQ by about 30% and up to 55% when both HT and HL were applied together. This trend continued after 6 days at HT-NL and HT-HL. During the 5 days period under optimum conditions a negligible increase of values of NPQ was detected, but did not reach values for plants at NT-NL.