【目的】探究变温环境下山桐子(Idesia polycarpa)种子萌发过程中代谢变化的重要代谢途径、关键过程的调控及其作用机理。【方法】以 5 ℃处理 60 d后解除休眠的山桐子种子为试验材料,在 15 ℃ 12 h/25 ℃ 12 h的培养箱中进行萌发试验,并于种皮开裂、露白、胚根伸长3个阶段取样,采用高效液相色谱法HPLC测定种子中吲哚乙酸(IAA),脱落酸(ABA)、赤霉素(GA₃)、玉米素(ZR)的含量;采用UPLC-MS/MS的方法对山桐子种子萌发期代谢组学进行分析。【结果】m(GA₃)/m(ABA)、m(ZR)/m(ABA)、m(IAA)/m(ABA)与m((IAA+GA₃+ZR)/m(ABA)在萌发过程中两者间含量差异达显著水平(P <0.05);数据显示种子萌发过程中存在515个差异代谢物,涉及氨基酸、核苷酸、脂质、有机酸、酚酸类等6大类物质。差异代谢物及富集通路数随着种子萌发生长而逐渐增加。【结论】山桐子种子萌发的生理策略是长期环境适应的结果,模拟季节性温差的变温环境更有利于种子萌发。ZR、GA₃含量增加与ABA含量下降是山桐子萌发的主要原因。在萌发前期,半乳糖代谢较为剧烈;萌发后期较前期差异代谢物增多,这与其萌发期代谢活动趋于旺盛有关。多种氨基酸及其衍生物随着种子萌发进程推进而含量增加;与渗透压调节相关的肌醇和胆碱类等代谢物变化明显;脂质的代谢在整个萌发过程中差异较大,尤其在不饱和脂肪酸的合成与代谢方面。

【Objective】In this study,experiments were carried out to explore the important metabolic pathways, key processes and mechanisms of metabolic changes in seed germination under variable temperature environment.【Method】The seeds of the Idesia polycarpa, which were released from dormancy after 60 days of low-temperature treatment at 5 ℃, were used for germination test in an incubator at 15 ℃ for 12 h/25 ℃ for 12 h. Samples were taken at three stages: seed coat dehiscence, whitening, and radicle elongation. The contents of indoleacetic acid (IAA), abscisic acid (ABA), gibberellin (GA₃) and zeatin (ZR) were determined by HPLC (high performance liquid chromatography), and the metabolomics at the germination stage of Idesia polycarpa seeds was analyzed by UPLC (ultra performance liquid chromatography) and MS/MS (tandem mass spectrom-etry).【Result】During the germination process, the differences in the contents of m(GA₃)/m(ABA), m(ZR)/m(ABA), m(IAA)/m(ABA) and m(IAA+GA₃+ZR)/m(ABA) among different germination stages reached a significant level (P<0.05). Metabolomic data revealed that there were 515 differential metabolites during seed germination, involving six major classes of substances, which including 101 kinds of amino acids and their derivatives, 103 kinds of phenolic acids, 49 kinds of nucleotides and their derivatives, 128 kinds of lipids, 65 kinds of other classes (including 51 kinds of sugars and alcohols, 14 kinds of vitamins), and 59 kinds of organic acids. Additionally, the number of differential metabolites and the pathways of enriched pathways gradually increased with seed germination and growth.【Conclusion】The physiological strategy of seed germination is the result of long-term environmental adaptation, and the variable temperature environment simulating seasonal temperature difference is more conducive to seed germination. The increase of ZR and GA₃ content and the decrease of ABA content were the main reasons for the germination of I. polycarpa. In the early stage of germination, galactose metabolism was more intense. The differential metabolites increased in the late stage of germination compared with the early stage, which was related to the vigorous metabolic activity in the germination stage. The contents of amino acids and their derivatives increased with the process of seed germination. The metabolites such as inositol and choline related to osmotic pressure regulation changed obviously. Lipid metabolism varies greatly during germination, especially in the synthesis and metabolism of unsaturated fatty acids.