Abstract: Taking Rumex K-1 leaves as test materials, this paper studied the role of mitochondrial alternative oxidase (AOX) pathway in photoprotection under different light intensities. Under low light intensity (200 μmol·m^-2·s^-1), and after treated with salicylhydroxamic acid to inhibit the AOX pathway, the leaf actual photochemical efficiency of PSⅡ, linear electron transport rate of photosynthesis, and photosynthetic O₂ evolution rate all decreased significantly while the non Q_B reducing reaction center had a significant increase, indicating that under low light, the photoinhibition was aggravated while the scavenging enzymes of reactive oxygen species (ROS) increased, which avoided the over-accumulation of ROS and partially alleviated the photoinhibition of Rumex K-1 leaves. Under high light intensity (800 μmol·m^-2·s^-1), the inhibition of AOX pathway caused more severe photoinhibition, and the increased activities of ROS scavenging enzymes  were insufficient to prevent the overaccumulation of ROS. This study demonstrated that AOX pathway played an important role in the photoprotection in Rumex K-1 leaves under both high and low light intensities, and the role of AOX pathway in photoprotection under high light could be irreplaceable by the other photoprotection pathways in chloroplast.

Key words: RumexK-1, salicylhydroxamic acid, mitochondrial alternative oxidase pathway, photoinhibition, photoprotection.