• ISSN 1008-505X
  • CN 11-3996/S

褪黑素提高大豆抗低磷胁迫的关键形态和生理指标

The key morphological and physiological indicatores for melatonin to promote the resistance of soybean to low phosphorus stress

    摘要
  • 摘要:
    目的 我们从根系形态和生理特征的角度研究了褪黑素提高大豆幼苗抗低磷胁迫的途径。
    方法 采用1片复叶期的大豆幼苗为材料进行了沙培试验。设置营养液中磷水平0.5 mmol/L为正常磷对照，0.05 mmol/L为低磷胁迫，磷胁迫下淋浇100 μmol/L褪黑素为褪黑素处理(P0.05+M)，在褪黑素处理后的0、5、10、15和20天，破坏性取大豆幼苗地上部(植株)和根部样品，调查大豆幼苗根系和地上部生长相关的形态和生理指标，分析了褪黑素与各指标之间的关系。
    结果 与CK相比，P0.05处理显著抑制了大豆幼苗和根系生长。与P0.05处理相比，第5、10、15和20天，P0.05+M处理大豆根系谷氨酰胺合成酶(GS)、谷氨酸合成酶(GOGAT)、谷氨酸脱氢酶(GDH)、谷氨酸-草酰乙酸转移酶(GOT)、谷氨酸-丙酮酸转氨酶(GPT)活性、可溶性蛋白、游离氨基酸含量平均提高幅度分别为10.63%、4.3%、4.8%、13.73%、6.18%、7.05%、5.23%，而铵态氮、硝态氮含量降低了9.7%、5.41%。褪黑素处理后第10和20天，P0.05+M处理大豆根长、根体积、根瘤数、根表面积、平均直径、根尖数、根系活力较P0.05处理相比平均提高了4.59%、27.51%、12.67%、7.27%、3.57%、22.23%、11%；叶、茎、根以及全株氮素和磷素积累量平均提高了108.37%、201.82%、58.93%、87.38%和62.69%、63.24%、55.84%、59.96%；叶片Chla、Chlb、Chl(a+b)、Car含量和气体交换参数Pn、Gs、Ci、Tr平均提高了13.02%、23.02%、15.66%、29.59%和16.64%、10.4%、3.2%、13.04%；株高、茎粗、叶面积、节数、叶干重、茎干重、根干重、全株干物质积累量平均提高了22.88%、17.09%、62.07%、20.97%、52.43%、25.6%、33.93%、38.58%。Mantel检测结果显示，大部分根系形态和生理指标之间，以及他们与大豆植株地上部形态、干物质积累、氮和磷素积累量呈显著正相关关系；随机森林分析进一步明确了根系硝态氮含量、谷氨酸-丙酮酸转氨酶活性、根表面积和铵态氮含量是决定低磷胁迫下大豆幼苗生长速率的4个关键指标。
    结论 根系硝态氮含量、谷氨酸-丙酮酸转氨酶活性、根表面积和铵态氮含量是决定低磷胁迫下大豆幼苗生长速率的4个关键指标。磷胁迫严重抑制了大豆幼苗根系的生长发育和生理代谢。淋浇褪黑素显著提高了根表面积，以及根系谷氨酸-丙酮酸转氨酶(GPT)活性，促进了根系中硝态氮和铵态氮达到向上转移，进而改善了大豆根系和全株的氮素和磷素积累，提高了光合效率，最终提升了大豆幼苗对低磷胁迫的抗性。

     

    Abstract:
    Objectives We analyzed the key indicators for melatonin to promote the resistance of soybean seedlings to low phosphorus stress, from the perspective of regulating root morphology and physiological characteristics.
    Methods Soybean seedlings at 1 compound leaf stage (V1 stage) were used as materials to carry out a sand culture experiment. The P concentration 0.5 and 0.05 mmol/L were set up as normal phosphorus control (CK) and low P stress (P0.05), and applying 100 μmol/Lof melatonin under low P stress was taken as melatonin treatment (P0.05+M). At the 0, 5, 10, 15, and 20 days after the melatonin treatment, soybean plants and roots were sampled for investigation of plant growth, root morphological indicators, and the determination of physiological indicators.
    Results Compared with CK, P0.05 treatment significantly inhibited the growth of soybean seedlings. Compared with the P0.05 treatment, on days 5, 10, 15, and 20, the P0.05+M treatment increased the activities of glutamine synthetase (GS), glutamate synthetase (GOGAT), glutamate dehydrogenase (GDH), glutamate oxaloacetate transferase (GOT), glutamate pyruvate transaminase (GPT), and the contents of soluble protein and free amino acids in roots by an average of 10.63%, 4.3%, 4.8%, 13.73%, 6.18%, 7.05%, 5.23%, but decreased ammonium and nitrate nitrogen content by 9.7% and 5.41%, respectively. On the 10th and 20th days, the P0.05+M treatment increased soybean root length, root volume, number of root nodules, root surface area, average diameter, number of root tips, and root vitality by an average of 4.59%, 27.51%, 12.67%, 7.27%, 3.57%, 22.23%, and 11% compared to the P0.05 treatment; The average nitrogen and phosphorus accumulation of leaves, stems, roots, and the whole plant increased by 108.37%, 201.82%, 58.93%, 87.38%, and 62.69%, 63.24%, 55.84%, and 59.96%, respectively; The content of photosynthetic pigments Chla, Chlb, Chl (a+b), Car and gas exchange parameters Pn, Gs, Ci, Tr increased by an average of 13.02%, 23.02%, 15.66%, 29.59% and 16.64%, 10.4%, 3.2%, 13.04%, respectively; The average increase in plant height, stem thickness, leaf area, number of nodes, leaf dry weight, stem dry weight, root dry weight, and total plant dry matter accumulation was 22.88%, 17.09%, 62.07%, 20.97%, 52.43%, 25.6%, 33.93%, and 38.58%, respectively. The Mantel test results showed that there was a positive correlation between most root morphological and physiological indicators, as well as between them and the aboveground dry matter, nitrogen, and phosphorus accumulation. Random forest analysis further clarified that root nitrate nitrogen content, glutamate pyruvate transaminase activity, root surface area, and ammonium nitrogen content were the four most critical indicators determining the growth rate of soybean seedlings under low phosphorus stress.
    Conclusions The most important indicators directly influencing root morphology and physiological activates were root nitrate nitrogen content, glutamate pyruvate transaminase activity, root surface area, and ammonium nitrogen content. Melatonin application significantly improved root development and the activities of glutamate pyruvate transaminase, stimulated the up-translocation of nitrogen and phosphorus in roots, thus alleviated the low phosphorus stress.

     

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