Required during nonphotochemical quenching (PubMed:17573537). Involved in NAD(P)H dehydrogenase complex-mediated chlororespiratory electron transport which mediates electron flow from stromal reductants to the plastoquinone (PQ) pool during chlorophyll fluorescence increase after turning off actinic light, in response to photoinhibition conditions (e.g. high light intensities), and upon long-term mild heat stress (PubMed:17573537). Additional isoforms seem to exist. Normal growth and photosynthesis in normal conditions (PubMed:17573537). Intact NDH complex, but altered NDH-dependent chlorophyll fluorescence increase after turning off actinic light and lower capacity for nonphotochemical quenching in high light intensities, due to altered nonphotochemical reduction of the plastoquinone (PQ) (PubMed:17573537). Increased sensitivity to photoinhibition and long-term mild heat stress (PubMed:17573537).