了解水培生菜生长的动态变化,抗坏血酸(AsA)池和在两种不同的黑暗时期光强度下的代谢(LL,20μmol·m-2·s-1;CL,200μmol·m-2·s-1)的连续光和正常光(NL,0μmol·m-2·s-1)由红色(R)和蓝色(B)LED提供,叶绿素荧光参数,抗坏血酸池大小,AsA代谢相关酶活性,在光照处理后0、8、16、24、32、40、48、56、64和72h测量生菜的H2O2含量,并在光照处理后第9天测量生菜的生长参数。结果表明,与NL相比,CL处理9天显着增加了生物量,干物质含量,和生菜的特定叶重,但对叶面积和根冠比没有显著影响;LL对生菜生物量没有显著影响,但这会降低根冠比。与NL相比,光处理后8小时内(在第一个黑暗期结束时),CL的AsA含量显着增加,然后保持在相对稳定的水平,略有增加;NL和LL之间的AsA含量没有显着差异,表现出相同的昼夜节律特征。总的来说,L-半乳糖-1,4-内酯脱氢酶(GalLDH)的活性,抗坏血酸过氧化物酶(APX),单脱氢抗坏血酸还原酶(MDHAR),CL下的谷胱甘肽还原酶(GR)在三种处理中最高,与其他两种处理的差异在几个时间点达到显著水平;GalLDH的活性几乎没有显著差异,APX,MDHAR,NL和LL之间的GR;在不同处理下,脱氢抗坏血酸还原酶(DHAR)活性没有显着差异。与NL相比,CL在处理后0-8小时内引起生菜PSⅡ最大光化学效率(Fv/Fm)急剧下降,然后稳定在相对稳定的水平;LL下的Fv/Fm值几乎与NL相同。除了32小时,在整个实验期间,CL条件下生菜的H2O2含量在三种处理中最高,并且在几个时间点显著高于NL;LL的H2O2含量与NL几乎相同。总之,生菜生物量,AsA含量,AsA代谢相关酶活性,叶绿素荧光参数,H2O2含量受连续光的暗期光强度而不是连续光信号的调节。
To understand the dynamic changes of hydroponic lettuce growth, ascorbate (AsA) pool and metabolism under two different dark period light intensities (LL, 20 μmol·m-2·s-1; CL, 200 μmol·m-2·s-1) of continuous light and normal light (NL, 0 μmol·m-2·s-1) provided by red (R) and blue (B) LEDs, the chlorophyll fluorescence parameters, ascorbate pool size, AsA metabolism-related enzyme activities, and H2O2 contents of lettuce were measured at 0, 8, 16, 24, 32, 40, 48, 56, 64, and 72 h after light treatment and the lettuce growth parameters were measured on the 9th day after light treatment. The results showed that compared with the NL, CL treatment for 9 days significantly increased the biomass, dry matter content, and specific leaf weight of lettuce, but had no significant effect on the leaf area and root-to-shoot ratio; LL had no significant effect on lettuce biomass, but it would reduce the root-shoot ratio. Compared with the NL, the AsA content of CL increased significantly within 8 h after light treatment (at the end of first dark period), and then maintained at a relatively stable level with a slight increase; there was no significant difference in AsA contents between NL and LL showing the same circadian rhythm characteristics. Overall, the activities of L-galactono-1,4-lactone dehydrogenase (GalLDH), ascorbate peroxidase(APX), monodehydroascorbate reductase (MDHAR), and glutathione reductase (GR) under CL were the highest among the three treatments, and the differences with the other two treatments reached significant levels at several time points; there was almost no significant difference in the activities of GalLDH, APX, MDHAR, and GR between NL and LL; there was no significant difference in the activities of dehydroascorbate reductase (DHAR) under different treatments. Compared with the NL, CL caused a sharp decrease of PSⅡ maximal photochemical efficiency (Fv/Fm) in lettuce within 0-8 h after treatment, which then stabilized at a relatively stable level; the Fv/Fm value under the LL was almost the same as the NL. Except for 32 h, the H2O2 content of lettuce under CL was the highest among the three treatments during the entire experimental period, and was significantly higher than that of NL at several time points; the H2O2 content of LL was almost the same as NL. In summary, lettuce biomass, AsA contents, AsA metabolism-related enzyme activities, chlorophyll fluorescence parameters, and H2O2 contents were regulated by the dark period light intensities of continuous light rather than continuous light signals.