Respiratory burst oxidase homologue-dependent H2 O2 and chloroplast H2 O2 are essential for the maintenance of acquired thermotolerance during recovery after acclimation.Thermotolerance is improved by heat stress (HS) acclimation, and the thermotolerance level is "remembered" by plants.  When spraying the NADPH oxidase inhibitor, diphenylene iodonium, after HS acclimation, the NADPH-H2 O2 level significantly decreased, resulting in a decrease in the expression of HS-responsive genes and the loss of maintenance of acquired thermotolerance (MAT). 
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