| To investigate the regulation mechanism of exogenous hydrogen sulfide (H2S) on chilling tolerance in cucumber(Cucumis sativa L.) plants.’Jinyou 3’ cucumber plants were used as materials. The respond of endogenous H2S to chilling tress, and the effect of sodium hydrosulfide (NaHS, the donor of H2S) on photosynthesis, antioxidant system and the yield of cucumber were investigated, by the methods of foliar spray and soaking seed. Distilled water was used as control. The results are as follows:1. The H2S production and L-/D-Cysteine desulfhydrase (CDes) activities were significantly increased during the first 4 h of chilling stress, and followed by a decrease. Cucumber seedlings treated with 1.0 mmol · L-1 NaHS by foliar spray or soaking seed methods showed significant higher H2S and CDes activity than the deionized water treated seedlings during the experiment. However, little differences were found between seedlings treated with aminooxyacetic acid hemihydrochloride (AOA, H2S inhibiter) or hypotaurine (HT, H2S scavenger) and the control seedlings. This indicated that H2S which is catalyzed by CDes was induced by chilling stress. Exogenous NaHS can enhance CDes activity and stimulated H2S emission.2. After 5 days of chilling stress, the electrolyte leakage (EL) and chilling injury index increased remarkably in all treatments. However, the extent of increase in EL and chilling injury index was lower in NaHS treatment, while not significantly different in AOA and HT treatments, compared with the water treatment. This data suggest that H2S can alleviate the damage to cell membrane, and improve the chilling tolerance of cucumber seedlings.3. Low temperature led to decrease in photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and activities of ribulose bisphosphate carboxylic enzyme (RuBPCase), fructose bisphosphatase (FBPase), and transketolase (TK), while increase in intercellular CO2 concentration (Gi). Chilling stress also caused a decrease in maximum photochemical efficiency of PSII in darkness (Fv/Fm), actual photochemical efficiency of PSⅡ (ΦPSⅡ), electron transport rate (ETR) and photochemical quenching (qP), whereas, an increase in initial fluorescence (Fo) and non-photochemical quenching (NPQ). Compared with the control, NaHS treatment remarkably increased Pn, Gs, Tr, activities of RuBPCase, FBPase and TK, Fv/Fm, ΦPSⅡ, ETR and qP, whereas decreased Ci, Fo and NPQ. Nevertheless, AOA and HT had no significant effect on them. This data revealed that H2S alleviated the damage on the photosynthetic apparantus in cucumber seedlings, and maintained higher carbon assimilation during chilling stress.4. Malondialdehyde (MDA) content in cucumber seedlings increased gradually during chilling stress days. The activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR), as well as the contents of reduced glutathione (GSH) and ascorbic acid (AsA) increased in the early days of chilling stress, but subsequently decreased. Compared with the control, NaHS caused a significant decrease in MDA content, but an increase in activities of SOD、POD、CAT、APX and GR, and the contents of GSH and AsA. However, the antioxidant enzymes activity and contents of GSH and AsA were not significantly affected by AOA and HT.5. Foliar spray 1.0 mmol · L-1 NaHS alleviated the effect of cold snap on the growth and development, photosynthesis, and enhanced antioxidant system activity in cucumber grown in solar-greenhouse. The yield of NaHS-treated cucumber plants was 15.3% higher than that of the control. |
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