论文部分内容阅读
为明确碱胁迫对小麦(Triticum aestivum)根系离子组及代谢组的影响,探讨其响应变化规律及机制,该研究以小麦为实验材料,采用两种碱性盐(Na HCO3和Na2CO3)按摩尔比1:1混合模拟不同碱胁迫强度,利用气相色谱-质谱联用(GC-MS)技术结合多元变量分析方法,系统分析小麦根系在碱胁迫下的矿质元素、游离阴离子、代谢产物及代谢途径变化。结果显示:低浓度碱胁迫下小麦根系仍能维持一定的生长,但在高浓度碱胁迫下根系生长受到了明显抑制。当碱胁迫强度超过小麦根系调节能力时,根系中Na含量急剧增加的同时K含量明显减少。碱胁迫刺激根中Ca积累,而Mg、Cu和Fe含量呈现下降趋势。碱胁迫明显减少根中游离阴离子(主要是Cl–)含量。检测代谢物组包括有机酸、氨基酸、碳水化合物、嘧啶和嘌呤等70个代谢产物,主成分分析结果表明代谢物均分布在95%的置信区间内。碱胁明显迫促进苹果酸、琥珀酸等代谢物积累,但造成糖类(果糖、蔗糖)及多元醇(肌醇、山梨糖醇)和氨基酸(γ-氨基丁酸、丙氨酸)含量显著下降。结果表明:根系中Na+含量剧增,加上高pH值危害,导致根系生长率降低;与此同时,游离阴离子明显减少,造成根系内负电荷亏缺和pH不稳定,导致离子平衡遭到破坏,进而引起一系列代谢途径的协变反应。小麦根系在碱胁迫下糖酵解、细胞膜脂代谢和氨基酸合成受到明显的抑制,但三羧酸循环显著增强。这些结果表明碱胁迫(高pH值)对碳素合成和储存有明显的负效应,降低代谢合成碳骨架和能量,使得清除活性氧能力明显下降。碱胁迫下根外部质子缺乏造成NO3–含量降低,影响氮素吸收利用,导致氨基酸合成受阻。三羧酸循环增强为生成有机酸类化合物和调控pH平衡提供能量,这可能是植物适应碱胁迫的一种特殊对应策略。
In order to clarify the effect of alkaline stress on ion groups and metabolites in roots of wheat (Triticum aestivum), the variation and mechanism of its response were discussed. Wheat was used as the experimental material. Two kinds of basic salts (Na HCO3 and Na2CO3) 1: 1 was used to simulate different alkali stress intensities. The mineral elements, free anions, metabolites and metabolic pathways of wheat roots under alkaline stress were systematically analyzed by gas chromatography-mass spectrometry (GC-MS) combined with multivariate analysis. . The results showed that under low alkali stress, the growth of wheat roots could still be maintained, but the root growth was inhibited obviously under high alkali stress. When the alkali stress intensity exceeded the regulation ability of wheat root, the content of Na in the root increased sharply while the K content decreased obviously. Alkali stress stimulated the accumulation of Ca in the roots, while the contents of Mg, Cu and Fe showed a downward trend. Alkali stress significantly reduced the contents of free anions (mainly Cl-) in roots. The test metabolites included 70 metabolites such as organic acids, amino acids, carbohydrates, pyrimidines and purines. The principal component analysis showed that the metabolites were all within 95% confidence interval. Alkali stress obviously promoted the accumulation of metabolites such as malic acid and succinic acid, but the contents of carbohydrates (fructose, sucrose) and polyols (inositol and sorbitol) and amino acids (γ-aminobutyric acid and alanine) were significantly increased decline. The results showed that the rapid increase of Na + content in roots and the increase of pH value resulted in the decrease of root growth rate. At the same time, the amount of free anions decreased obviously, leading to negative charge deficit and pH instability in root system, resulting in the destruction of ion balance , Which in turn led to a series of metabolic pathways covariant response. Under alkaline stress, the wheat roots underwent glycolysis, lipid metabolism and amino acid synthesis were significantly inhibited, but the TCA cycle was significantly enhanced. These results indicate that alkali stress (high pH) has a significant negative effect on carbon synthesis and storage, reducing the metabolic carbon backbone and energy metabolism, resulting in a significant decrease in the ability to scavenge reactive oxygen species. Under alkaline stress, the lack of proton outside the root causes the decrease of NO3- content, which affects the absorption and utilization of nitrogen, resulting in the obstruction of amino acid synthesis. The enhancement of tricarboxylic acid cycle provides energy to generate organic acids and regulate pH balance, which may be a special countermeasure for plants to adapt to alkali stress.