| This study was conducted to determine the influences of exogenous EBR (24-epibrassinolide) on the photosynthetic characteristics, antioxidant systems and pesticide degradation metabolism of wine grape variety Cabernet Sauvignon, and to explore EBR-induced alleviation of pesticide damage to the vines and its role in reducing pesticide residue. Using wine grape variety Cabernet Sauvignon (Vitis vinifera L.) potted seedlings as the experimental material, effects of EBR on the photosynthetic gas exchange characteristics, chlorophyll fluorescence parameters, reactive oxygen species and malondialdehyde contents, antioxidant substances content, detoxification enzyme activities and chlorothalonil residue in grape leaf were investigated. In comparison to the control, 0.1 mg·L-1 EBR treatment alone could improve photosynthetic characteristics in grape leaf, and chlorothalonil treatment (600 times diluent) had an inhibiting effect. Compared with the CHT treatment, EBR+CHT treatment could improve leaf net photosynthetic rate (Pn), stomatal conductance (Gs), as well as intercellular CO2 concentration (Ci) significantly, and it could also increase photosynthetic system II (PSII), photochemical conversion rate (Fv/Fm), actual photochemical efficiency (ΦPSII) and photochemical quenching coefficient (qP) significantly. Compared with the control, chlorothalonil treatment could cause significant increase of hydrogen peroxide (H2O2), superoxide anion (O-·2) and malondialdehyde (MDA) contents in grape leaf, while EBR+CHT treatment made them decreased by 33.4%, 15.8% and 6% respectively compared with CHT treatment and also it made glutathione (GSH) and ascorbic acid (AsA) contents increased by 5.6% and 18.2% on average. Exogenous 0.1 mg·L-1 EBR treatment alone and CHT treatment could both enhance activities of peroxidase (POD), glutathione-s-transferase (GST) and glutathione reductase (GR) in grape leaves significantly, and EBR+CHT treatment could further enhance enzyme activities compared with CHT treatment. EBR pretreatment accelerated the degradation of chlorothalonil in leaves and reduced the pesticide residues significantly. In conclusion, 0.1 mg·L-1 EBR treatment alone could promote grape leaf photosynthesis and increase antioxidant contents as well as detoxification enzyme activities, and chlorothalonil treatment (600 times diluent) damaged the normal photosynthesis and redox balance of grape leaves, while exogenous 0.1 mg·L-1 EBR pretreatment could improve leaf photosynthesis and reduce the accumulation of reactive oxygen species and MDA. It could also enhance detoxification enzyme activities to promote the degradation of chlorothalonil in leaves, so as to mitigate the harm of pesticide on plants. |