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 kg/hm2、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%)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、氧扩散速率和呼吸速率分别提高了10.9%、14.83%和21.84%(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),而铵态氮和碱解氮含量分别降低了7.05%和12.29%(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重要理论支持。

       

      Abstract: Understanding how irrigation and fertilization strategies modulate root-soil interactions is critical for optimizing crop productivity and soil health in greenhouse systems. Root exudates act as key mediators in rhizosphere biochemical processes, yet their response to variations in aerated irrigation and nitrogen levels remains insufficiently explored. To address this knowledge gap, this study employed non-targeted metabolomics to investigate how aerated drip irrigation and nitrogen application level affect the composition and metabolic pathways of root exudates in greenhouse-grown pepper (Capsicum annuum L.). This approach was selected for its high sensitivity and ability to comprehensively profile complex exudate mixtures, providing detailed insight into plant metabolic responses. A randomized block experiment was conducted with three nitrogen levels (zero level 0 kg/hm2, low level 140 kg/hm2, and conventional level 210 kg/hm2) and two irrigation methods (conventional drip irrigation: air void fraction 0%; aerated drip irrigation: air void fraction 15%). Results showed that compared with conventional drip irrigation, aerated drip irrigation significantly increased soil oxygen diffusion rate (ODR), oxidation-reduction potential (ORP) and soil respiration rate by 10.9%, 14.83%, and 21.84%, respectively (P<0.05). In addition, aerated drip irrigation changed the soil nitrogen conversion process, and the nitrate nitrogen content by 13.11% (P<0.05) and unease activity by 9.68% (P<0.05), while reducing ammonium nitrogen and alkali-hydrolyzable nitrogen by 7.05% and 12.29%, respectively (P<0.05). These metabolite changes indicate synergistic effects of irrigation oxygenation and nitrogen availability on root metabolic outputs. Liquid chromatography-mass spectrometry (LC-MS) identified 321 compounds in positive ion mode and 167 in negative ion mode, mainly including lipids, lipid-like molecules, organic acids, and their derivatives. Compared with conventional drip irrigation, 38, 49 and 45 significantly different metabolites were screened out by aerated drip irrigation, including 17, 26 and 29 metabolites with no nitrogen application, low nitrogen and conventional nitrogen, respectively, and 21, 23 and 16 down-regulated metabolites. The discovery of these differential metabolites provides a key clue for further exploring the regulatory effect of aerated drip irrigation and nitrogen fertilization on root exudate metabolism in pepper. KEGG pathway analysis revealed significant enrichment in glycine, serine, and threonine metabolism, as well as in ABC transporter pathways. Redundancy analysis showed that soil environmental factors explained 43.36% of the variation in root exudate profiles, with ODR, ORP, and nitrate nitrogen identified as key drivers. This study demonstrates that aerated drip irrigation plays a crucial role in influencing the metabolism of root exudates in peppers by regulating the soil environment. This finding not only enriches our understanding of the mechanisms by which aerated drip irrigation and nitrogen application interact in the cultivation of peppers, but also provides important theoretical support and practical evidence for the development of a highly efficient cultivation model for peppers based on metabolic regulation.

       

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