以苋菜（Amaranthus tricolor Linn.）品种‘苏苋1号’（‘Suxian No. 1’）为试验材料，比较了不同温度〔25 ℃（对照）、20 ℃、15 ℃和10 ℃〕处理下苋菜株高以及叶片中甜菜色素含量、叶绿素含量和叶绿素荧光参数的变化，并探究了温度对苋菜光合特性及光合作用相关基因表达的影响。结果显示：处理3 和6 d的苋菜株高以及叶片中甜菜色素和叶绿素含量随着温度降低呈现降低的趋势，叶片的PSⅡ最大光化学效率（Fv/Fm）、PSⅡ实际光量子产额〔Y(Ⅱ)〕、相对电子传递速率（rETR）、非光化学淬灭系数（qN）和调节性能量耗散的量子产量〔Y(NPQ)〕总体呈现波动降低的趋势，非调节性能量耗散的量子产量〔Y(NO)〕呈现波动升高的趋势；其中，15 ℃和10 ℃处理下苋菜的株高以及叶片中甜菜色素和叶绿素含量极显著低于对照，10 ℃处理下叶片的Fv/Fm、Y(Ⅱ)、rETR、qN和Y(NPQ)值总体极显著低于对照，Y(NO)值则极显著高于对照。qRT-PCR结果显示：总体上看，苋菜叶片AtrPPCK、AtrPEPC、AtrMDH、AtrNADP-MDH、AtrNAD-ME、AtrNADP-ME和AtrPPDK基因的相对表达量在多数温度下处理3和6 d与对照有显著差异；温度较低（10 ℃）会抑制除了AtrPPCK基因外的其他基因的表达，随着处理时间延长，基因相对表达量略有回升。相关性分析结果显示：温度与处理3和6 d苋菜的株高以及叶片中甜菜色素含量、叶绿素含量和多数叶绿素荧光参数呈极显著或显著相关。综合分析结果显示：低温会降低苋菜的叶绿素含量，破坏光合系统，抑制光合作用相关基因的表达，从而降低甜菜色素含量，抑制苋菜生长。

Taking cultivar ‘Suxian No. 1’ of Amaranthus tricolor Linn. as test material, variations of plant height and betalain content, chlorophyll content, and chlorophyll fluorescence parameters of leaf of A. tricolor under different temperature 〔25 ℃ (the control), 20 ℃, 15 ℃, and 10 ℃〕 treatments were compared, and effects of temperature on photosynthetic characteristics and photosynthesisrelated genes were investigated. The results show that plant height and contents of betalain and chlorophyll in leaf of A. tricolor treated for 3 and 6 d show a tendency to decrease with the decrease of temperature, maximum photochemical efficiency of PSⅡ (Fv/Fm), effective quantum yield of PSⅡ 〔Y(Ⅱ)〕, relative electron transport rate (rETR), nonphotochemical quenching coefficient (qN), and quantum yield of regulated energy dissipation 〔Y(NPQ)〕 of leaf show a fluctuation decrease tendency in general, and quantum yield of non-regulated energy dissipation 〔Y(NO)〕 shows a fluctuation increase tendency; in which, plant height and contents of betalain and chlorophyll in leaf of A. tricolor under 15 ℃ and 10 ℃ treatments are extremely significantly lower than those of the control, Fv/Fm, Y(Ⅱ), rETR, qN, and Y(NPQ) values of leaf under 10 ℃ treatment are extremely significantly lower than those of the control, while Y(NO) value is extremely significantly higher than that of the control. The qRT-PCR result shows that the relative expression levels of AtrPPCK, AtrPEPC, AtrMDH, AtrNADP-MDH, AtrNAD-ME, and AtrNADP-ME, and AtrPPDK genes in leaf of A. tricolor under most temperature treatments for 3 and 6 d are significantly different from those of the control in general; relatively low temperature (10 ℃) can suppress expression of all genes except AtrPPCK gene, and with the elongation of treatment time, relative expression levels of genes slightly elevate. The correlation analysis result shows that temperature shows extremely significant or significant correlations with plant height, contents of betalain and chlorophyll, and most chlorophyll fluorescence parameters of leaf of A. tricolor treated for 3 and 6 d. The comprehensive analysis result shows that low temperature will decrease the chlorophyll content of A. tricolor, impair the photosynthetic system, suppress the expression of photosynthesis-related genes, and thus decrease the betalain content and inhibit the growth of A. tricolor.