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加气滴灌和施氮对辣椒根系分泌物的影响

Effects of aerated drip irrigation and nitrogen application on root exudates of pepper

  • 摘要: 加气滴灌与施氮对温室辣椒根系分泌物的影响机制尚不明确。研究旨在通过非靶向代谢组学技术,探究加气滴灌与施氮对温室辣椒根系分泌物组成及代谢路径的调控效应。设置了3个施氮水平(不施氮0、低量施氮140 kg/hm2和常规施氮210 kg/hm2)及2个加气水平(常规滴灌:掺气比例0;加气滴灌:掺气比例15%)的随机区组试验。结果表明,与常规滴灌处理相比,加气滴灌下土壤氧化还原电位和氧扩散速率分别提高了10.90%和14.83%(P<0.05)。此外,加气滴灌改变了土壤氮素转化进程,硝态氮含量和脲酶活性分别提高了13.11%和9.68%(P<0.05),而铵态氮含量降低了7.05%(P<0.05)。通过液相色谱-质谱联用检测,在正离子模式下共鉴定出321种根系分泌物,负离子模式下鉴定出167种,主要包括脂类、有机酸及其衍生物、苯丙烷类和芳香族化合物等。加气滴灌相较于常规滴灌,不施氮、低量施氮和常规施氮分别筛选出38、49和45种显著差异代谢物,其中上调17、26、29种,下调21、23、16种。KEGG代谢通路分析显示,甘氨酸、丝氨酸和苏氨酸代谢及ABC转运蛋白通路显著富集。冗余分析显示,土壤环境对根系分泌物组成的解释度达43.36%,其中氧化还原电位、氧扩散速率和硝态氮为关键驱动因子。加气滴灌通过调节土壤环境在影响根系分泌物代谢中发挥关键作用,为构建基于代谢调控的加气滴灌辣椒高效栽培模式提供理论支持。

     

    Abstract: Irrigation and fertilization can be widely used to modulate the root-soil interactions in sustainable agriculture. It is also critical to optimize crop productivity and soil health in greenhouse systems. Root exudates can act as the key mediators in rhizosphere biochemical processes. Yet it is often required for their response to the variations in the aerated irrigation and nitrogen levels. In this study, the non-targeted metabolomics was employed to investigate the effects of the aerated drip irrigation and nitrogen application level on the composition and metabolic pathways of the root exudates in greenhouse-grown pepper (Capsicum annuum L.). The high sensitivity to profile complex exudate mixture was selected to provide some insight into the plant metabolic responses. A randomized block experiment was conducted with three nitrogen levels (zero level 0, low level 140 kg/hm2, and conventional level 210 kg/hm2) and two irrigation modes (conventional drip irrigation: air void fraction 0; and aerated drip irrigation: Air void fraction 15%). Results showed that the aerated drip irrigation significantly increased the soil oxygen diffusion rate (ODR) and oxidation-reduction potential (ORP) by 10.90% and 14.83%, respectively (P<0.05), compared with the conventional drip irrigation. In addition, aerated drip irrigation significantly altered soil nitrogen transformation. Compared to conventional drip irrigation, aerated drip irrigation significantly increased the nitrate nitrogen content by 13.11% (P<0.05) and unease activity by 9.68% (P<0.05), while reducing ammonium nitrogen by 7.05% on average (P<0.05). These changes indicate synergistic effects of irrigation-induced oxygenation and nitrogen availability on root-associated metabolic outputs. Liquid chromatography-mass spectrometry (LC-MS) was used to identify 321 compounds in the positive ion mode, and 167 in the negative ion mode, mainly including the lipids, lipid-like molecules, organic acids, and their derivatives. Compared with conventional drip irrigation, 38, 49 and 45 significantly different metabolites were identified under aerated drip irrigation at zero, low, and conventional nitrogen levels, respectively, including 17, 26 and 29 up-regulated metabolites, and 21, 23 and 16 metabolites were down-regulated. The identification of these differential metabolites provides important insights into the regulatory effects of aerated drip irrigation and nitrogen fertilization on root exudate metabolism in pepper. KEGG pathway analysis revealed that there was a significant enrichment in the glycine, serine, and threonine metabolism, as well as in ABC transporter pathways. Redundancy analysis showed that the soil environmental factors explained 43.36% of the variation in the root exudate profiles, where the ODR, ORP, and nitrate nitrogen were identified as the key drivers. The aerated drip irrigation can play a crucial role in the metabolism of the root exudates in peppers under the soil environment. This finding can be expected to regulate the aerated drip irrigation and nitrogen application in the cultivation of the peppers. Important theoretical support and practical evidence can also be offered for a highly efficient cultivation model for peppers using metabolic regulation.

     

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