Sucrose metabolism and carbohydrate accumulation were evaluated in butterhead lettuce cultured under alternating red light (R) and blue light (B) irradiance. The R/B treatments were respectively R/B(5 m) (i.e. R 5 min/B 5 min), R/B(10 m), R/B(15 m), R/B(30 m) and R/B(60 m). Meanwhile, concurrent R and B (RB) as well as monochromatic R (R) and monochromatic B (B) were conducted. Compared with concurrent RB, all the alternating R/B treatments increased the fresh weight (FW), dry weight (DW) and the content of pigment and soluble sugar in lettuce on the basis of the same daily photon amount and electric energy consumption. Lettuce exposed to R/B(30 m) required the least number of photons (1.82 μmol) and electricity (1.04 MJ) per gram DW produced among all the treatments, thus R/B(30 m) was the recommended lighting mode in terms of the use efficiency of photons and electricity. Relatively higher soluble sugar content and the total sweetness index (TSI), as well as lower crude fiber content were detected in lettuce subjected to R/B(60 m), which was regarded as optimal irradiation mode in terms of lettuce taste. The content of sucrose, glucose and fructose, and the activities of sucrose phosphate synthase (SPS) and sucrose synthase (SS) in the synthesis direction, as well as the gene expression level of SPS in lettuce were all enhanced by the alternating irradiation of R/B (15 m), R/B (30 m) and R/B (60 m) in comparison to the concurrent RB treatment. Moreover, higher enzyme activities in the synthetic direction of sucrose were found to be accompanied with higher soluble sugar content in lettuce subjected to R/B (30 m), R/B (60 m) and the solely R, indicating that the enzyme activities in sucrose synthetic direction seemed more related to the soluble sugar accumulation in lettuce. The results also showed that SS in lettuce leaves mainly acted on sucrose decomposition rather than synthesis. The hexose (glucose and fructose) content of lettuce subjected to R/B(60 m) basically kept the highest level among all the treatments through the whole processing period, which might be due to that lettuce exposed to R/B (60 m) owned the highest gene expression level of SS and invertase, as well as the highest enzyme activities of SS (cleavage) and invertase among all the treatments. Solely B inhibited the gene expression of sucrose metabolism-related enzymes in lettuce, and the photon use efficiency to R by lettuce was higher than to B from the angle of biomass and soluble sugar accumulation. A low intensity of B (1/9 of the R level) alternating with R improved the photon and electric use efficiency of lettuce in this study.

在红光 (R) 和蓝光 (B) 交替辐照下培养的白头莴苣中评估了蔗糖代谢和碳水化合物积累。R/B处理分别为R/B(5 m)(即R 5 min/B 5 min)、R/B(10 m)、R/B(15 m)、R/B(30 m)和R /B（60 米）。同时，同时进行R和B（RB）以及单色R（R）和单色B（B）。与同时RB相比，R/B交替处理均增加了生菜的鲜重(FW)、干重(DW)以及色素和可溶性糖的含量，在相同的日光子量和电能消耗的基础上。在所有处理中，暴露于 R/B（30 m）的生菜每克 DW 所需的光子数（1.82 μmol）和电（1.04 MJ）最少，因此，就光子和电的利用效率而言，R/B(30 m)是推荐的照明模式。R/B(60 m)辐照处理的生菜中可溶性糖含量和总甜度指数(TSI)相对较高，粗纤维含量较低，这被认为是生菜味道的最佳辐照方式。R的交替照射增强了莴苣中蔗糖、葡萄糖和果糖的含量，以及蔗糖磷酸合酶（SPS）和蔗糖合酶（SS）在合成方向上的活性，以及​​SPS基因在莴苣中的表达水平。 /B (15 m)、R/B (30 m) 和 R/B (60 m) 与同时进行的 RB 处理相比。而且，R/B (30 m)、R/B (60 m) 和单独 R 的生菜中，在蔗糖合成方向上较高的酶活性伴随着较高的可溶性糖含量，表明蔗糖中的酶活性较高。合成方向似乎与生菜中可溶性糖的积累更相关。结果还表明，生菜叶片中的SS主要作用于蔗糖分解而非合成。R/B(60 m)生菜的己糖(葡萄糖和果糖)含量在整个加工期间基本保持在所有处理中的最高水平，这可能是由于生菜暴露于R/B(60 m)在所有处理中，SS和蔗糖酶的基因表达水平最高，SS（裂解）和蔗糖酶的酶活性最高。单用B抑制莴苣中蔗糖代谢相关酶的基因表达，从生物量和可溶性糖积累的角度看，莴苣对R的光子利用效率高于B。在本研究中，低强度 B（R 水平的 1/9）与 R 交替提高了莴苣的光子和电利用效率。