黄瓜富氢水浸种对低温下幼苗光合碳同化及氮代谢的影响

为探明外源氢气(H₂)对低温下黄瓜幼苗光合碳同化及氮代谢的影响,以‘津优35号’黄瓜为试材,将种子分别用饱和富氢水(HRW,H₂供体)和去离子水(对照,Control)浸种8h,常温下育苗,幼苗长至两叶一心时移至光照培养箱中进行低温(昼/夜温度8℃/5℃)处理。结果表明:低温抑制黄瓜幼苗的生长,造成叶片光合色素含量、光合速率(P_n)、气孔导度(G_s)、蒸腾速率(T_r)、光下实际光化学效率(Φ_PSⅡ)、PSⅡ。最大光化学效率(F_v/F_m)、光下最大天线转换效率(F_v^′/F_m^′)、核酮糖–1,5–二磷酸羧化酶(RuBPCase)活性和根系活力逐渐降低,而胞间CO₂浓度(C_i)和初始荧光(F₀)趋于升高。此外,低温胁迫诱导了黄瓜幼苗碳代谢关键酶蔗糖合成酶(SS)和蔗糖...

Effect of Exogenous Hydrogen on Photosynthetic Carbon Assimilation and Nitrogen Metabolism of Cucumber Seedlings Under Low Temperature

The purpose of this paper is to investigate the effect of exogenous hydrogen（H2）on photosynthetic carbon assimilation and nitrogen metabolism of cucumber（Cucumis sativus L.）under low temperature. The‘Jinyou 35’cucumber seedlings subjected to low temperature stress（day/night temperature was 8 ℃/5 ℃）were presoaked with hydrogen-rich water（HRW，the donor of H2）or the deionized water（Control）for 8 h. The results illustrated that the chilling stress restrained the seedling growth，and decreased the pigment contents，net photosynthetic rate（Pn），stomatal conductance（Gs），transpiration rate（Tr），actual photochemical efficiency of PSⅡ（ΦPSΠ），maximum photochemical efficiency of PSII in darkness（Fv/Fm），antenna efficiency of PSⅡ（Fv′/Fm′），the activity of ribulose bisphosphate carboxylicase（RuBPCase）and root activity，while increased the intercellular CO2 concentration（Ci）and initial fluorescence（F0）. Further studies revealed that chilling stress induced enhancement of sucrose synthetase（SS）and sucrose phosphate synthetase（SPS）activities and the total sugar，sucrose content，but reduced the starch content. Meanwhile，the total nitrogen content，ammonia nitrogen content and the activities of reduced nitrate reductase（NR），glutaminase（GS），glutamate synthase（GOGAT）and glutamate dehydrogenase（GDH）increased in the early days of chilling stress but subsequently decreased under low temperature stress. The nitrate nitrogen content increased gradually. These change tendencies of HRW treatment were almost the same as those of control. In addition to low Ci and F0，most of the remaining indicators in HRW treatment were significantly higher than control，which indicated that exogenous H2 could enhance the tolerance of cucumber seedlings to lower temperature stress by increasing the activities of key photosynthetic enzymes，reducing photoinhibition and maintaining a high level of carbon and nitrogen metabolism，thus promoting the cucumber seedlings growth finally.