Waterlogging has negative effects on plant growth, ethylene had been proposed to play an important role in stress responses. This study aims to investigate the role of ethylene in improving waterlogging tolerance of Zanthoxylum armatum, which is economically valuable but intolerant to waterlogging. To evaluate photosynthetic ability under waterlogging stress, exogenous ethylene with different concentration was applied to prior. The results showed that the expression of genes related to 'porphyrin and chlorophyll metabolism', as well as the content of chlorophyll and carotenoids were observed to decrease, along with the reduced activity of the RuBPCase and PEPCase enzymes. Furthermore, prolonged waterlogging reduced stomatal conductance (G(s)), net photosynthetic rate (P-n), transpiration rate (T-r), and water-use efficiency (WUE). The maximal efficiency of PSII photochemistry (Fv/Fm), actual PSII efficiency (& phi;PSII), and electron transport rate (ETR) also decreased with the duration of waterlogging, while the non-photochemical quenching coefficient (NPQ) showed a substantial increase. Both G(s) and & phi;PSII were the two critical physiological factors. Photosynthetic was increased with higher ethylene concentration under non-waterlogging, but the effectiveness of 200 & mu;mol L-1 ethylene was greater than 400 & mu;mol L-1 ethylene under waterlogging. Principal component analysis revealed Zardc34816 as the most important gene for photosynthesis, while Zardc52464 (ZaLIN2) was positively correlated with the pigments, enzyme activity, gas exchange, and chlorophyll fluorescence parameters. The results suggested that exogenous ethylene could be beneficial to promote the photosynthesis of Z. armatum under waterlogging stress.
