Abstract:The objective of this experiment was to investigate the reduced glutathione (GSH) participated in the effects of photosynthesis and fluorescence regulation pathway of exogenous nitric oxide (NO) in cucumber seedling leaves under low temperature (10 ℃/6 ℃) stress. The substratecultured ‘Jinyan No.4’ cucumber seedlings were used as the test materials. Fourleaf onehearted plants were set at a photoperiod of 14 h/10 h, day and night temperature of 25 ℃/20 ℃ in a light incubator, and leaf surface pretreatment with GSH synthase inhibitors (BSO, butanamine sulfoxide amine), NADPH synthetase inhibitor (6AN, 6amino nicotinamide), and nitric oxide NO donor (SNP, sodium nitroferrocyanide) after 8 hours The daynight temperature dropped to 10 ℃/6 ℃ 24 h after the first spraying, and cucumber leaves cell membrane permeability, gas exchange and chlorophyll fluorescence parameters and other changes were measured after 24 h of cold stress. The results showed that: (1) compared with the control, the SNP treatment significantly increased the relative water content, chlorophyll content, net photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (Gs), Maximum photochemical efficiency (Fv/Fm) of photosystem Ⅱ (ΦPSⅡ), the quantum yield of PSⅡ regulated energy dissipation (NPQ), photochemical quenching coefficient (qP), apparent photosynthetic electron transport rate (ETR), the relative fluorescence of the nitric oxide, the OJIP phase of rapid chlorophyll fluorescence induction curve of cucumber seedlings and maintain high fluorescence yield after 24 h of low temperature stress, significantly decreased intercellular CO2 concentration (Ci), alleviated continual enhancement of MDA content and the quantum yield of nonregulatory energy dissipation YNO. (2) Compared with SNP treatments, BSO+SNP and 6AN+SNP treatments significantly reduced the effect of SNP; SNP treatment of cucumber seedling leaves the maximal photochemical efficiency of primary photochemistry (φPo), the quantum yield of light energy absorption by PSⅡ reaction center for electron transfer (φEo) and the probability of capturing excitons for transporting electrons to other electron acceptors downstream of the electron transport chain QA (ψo), fluorescence parameters related to the acceptorside properties of the PSⅡ reaction center include the oxygen release complex (FOK), the reduction capacity of QA (FKJ), the reduction capacity of QB (FIP) and the density of active reaction centers per excited crosssection (RC/CS) were significantly higher than that of CK. (3) Compared with SNP treatment, the values of φPo, φEo, ψo, RC/CS, FKJ, FJI and FIP were significantly decreased in BSO+SNP and 6AN+SNP treatment, while Mo and VJ increased significantly. Under low temperature stress, GSH plays an important role in exogenous NO increasing the relative water content, reducing lipid peroxidation, stabilizing photosystem Ⅱ and promoting electron transfer capability of donor side and recipient side of electron transfer chain in PSⅡ reaction center and improved the cold resistance of cucumber seedlings.