Abstract: In order to explore the synergistic effect of exogenous silicon and salicylic acid on alleviating cadmium toxicity in tobacco seedlings, this paper took tobacco variety NC89 as experimental material and studied the effect of single exogenous silicon, salicylic acid treatment and their compound treatment by hydroponics on biomass, cadmium accumulation, antioxidant enzyme activity, chlorophy Ⅱ content and photosynthetic characteristics of tobacco seedlings under 100 μmol/L cadmium stress. The results showed that single exogenous silicon, salicylic acid treatment and their combined treatment could promote tobacco seedling growth, reduce cadmium accumulation and improve photosynthetic characteristics. Among them, the effect of combined treatment was the best, because the biomass of root, stem and leaf, Pn, Tr and WUE of leaf were significantly increased than those from cadmium stress treatment by 186.01%, 122.08%, 125.02%, 326.39%, 200% and 527.88%, respectively. While, the cadmium accumulation of root, stem and leaf, and intercellular CO2 concentration (Ci) were significantly reduced by 90.01%, 87.25%, 90.91% and 59.85%, respectively. Although compound treatment was effective in enhancing antioxidant capacity and chlorophyⅡ content of tobacco seedlings, single salicylic acid treatment had the best effect. Under single salicylic acid treatment, the content of MDA, activity of SOD, POD and CAT activities were decreased significantly by 41.21%, 31.36%, 32.37% and 22.55% than those under cadmium stress treatment. In addition, the contents of chlorophy Ⅱ a, chlorophy Ⅱ b and carotenoids increased significantly by 80.08%, 132.53% and 165.73%, respectively. In general, the combined use of exogenous silicon and salicylic acid could effectively relieve cadmium toxicity, reduce cadmium accumulation, increase biomass and improve photosynthetic capacity.

Key words: tobacco, silicon, salicylic acid, cadmium stress, physiological characteristics

摘要： 为了探究外源硅和水杨酸复合处理缓解烟草幼苗镉胁迫的协同效应，采用营养液水培法，以烟草品种NC89为试验材料，研究了单独和复合施用外源硅、水杨酸对100 μmol/L镉胁迫下烟草幼苗生物量、镉积累、抗氧化酶活性、叶绿素含量和光合特性的影响。结果表明：外源硅、水杨酸单独和复合处理均能促进镉胁迫下烟草幼苗生长、降低镉积累量、提高光合特性，其中以外源硅和水杨酸复合处理效果最好，烟草幼苗根、茎、叶生物量、叶片净光合速率（Pn）、蒸腾速率（Tr）和水分利用效率（WUE）分别较镉胁迫处理显著提高了186.01%、122.08%、125.02%、326.39%、200.00%和527.88%，根、茎、叶镉积累量及胞间CO2浓度（Ci）则分别显著降低了90.01%、87.25%、90.91%和59.85%。在改善镉胁迫下烟草幼苗抗氧化能力和叶绿素含量方面，外源硅及水杨酸复合处理亦发挥积极作用，但以水杨酸单独处理效果最好，其中烟草幼苗MDA含量、SOD、POD和CAT活性分别较镉胁迫处理显著降低了41.21%、31.36%、32.37%和22.55%，叶绿素a、叶绿素b和类胡萝卜素含量则分别显著提高了80.08%、132.53%和165.73%。综合来看，外源硅及水杨酸复合施用能有效缓解镉对烟草幼苗的毒害，在降低镉积累、提高生物量和光合作用能力方面发挥协同增效作用。

关键词: 烟草, 硅, 水杨酸, 镉胁迫, 生理特性