College of Agronomy, Heilongjiang Bayi Agricultural University, Daqing, People's Republic of China.
PLoS One. 2020 Dec 15;15(12):e0243537. doi: 10.1371/journal.pone.0243537. eCollection 2020.
Understanding the relationship between exogenous melatonin and water deficit stress is crucial for alleviating the effects of water deficit stress at germination stage of soybean (Glycine max (L.) Merrill) in agriculture. This study investigated the effects of exogenous melatonin on soybean antioxidant properties and cell ultrastructure under water deficit stress induced by polyethylene glycol (PEG) 6000. The drought-sensitive soybean variety Suinong 26 was used as the material to study the effects of different concentrations of melatonin (0, 300, 500 μmol·L-1) soaking soybean seeds under drought stress (PEG-6000: 3% and 6%). The results showed that the germination rate (GR), germination potential (GP), germination index (GI) and radicle shape of soybean were affected negatively to different degrees under PEG stress. Moreover, stress induced by different PEG concentrations overproduced the content of reactive oxygen species (H2O2, O2·-) in cells, leading to increased lipid membrane peroxidation as electrolyte leakage (EL) and malondialdehyde (MDA) content, which resulted in impaired cell integrity. However, after seeds soaking with melatonin, the lipid peroxidation of the cell membrane was reduced, and the activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) further increased to minimize the excessive generation of ROS. Similar results were obtained for soluble protein and proline, that may help in regulating the osmotic pressure and maintain cellular integrity. With the interaction of these enzymes, compared with 300 μmol·L-1 melatonin, 500 μmol·L-1 melatonin could more effective to remove the ROS and reduce cell peroxidation. Overall, 500 μmol·L-1 melatonin performed better than 300 μmol·L-1. In conclusion, the seed soaking with melatonin promoted the germination of soybean seeds under water stress.
了解外源性褪黑素与水分亏缺胁迫之间的关系对于缓解大豆（Glycine max (L.) Merrill）在农业中萌发阶段水分亏缺胁迫的影响至关重要。本研究探讨了外源性褪黑素对聚乙二醇（PEG）6000 诱导水分亏缺胁迫下大豆抗氧化特性和细胞超微结构的影响。以干旱敏感品种绥农 26 为材料，研究了不同浓度褪黑素（0、300、500 μmol·L-1）浸种对干旱胁迫下（PEG-6000：3%和 6%）大豆种子萌发的影响。结果表明，PEG 胁迫下大豆的发芽率（GR）、发芽势（GP）、发芽指数（GI）和根形状均受到不同程度的负向影响。此外，不同 PEG 浓度诱导的应激导致细胞内活性氧（H2O2、O2·-）含量增加，导致质膜过氧化加剧，电解质泄漏（EL）和丙二醛（MDA）含量增加，细胞完整性受损。然而，褪黑素浸种后，细胞膜的脂质过氧化程度降低，超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）和抗坏血酸过氧化物酶（APX）等抗氧化酶的活性进一步提高，以尽量减少 ROS 的过度产生。可溶性蛋白和脯氨酸也得到了类似的结果，这可能有助于调节渗透压并维持细胞完整性。在这些酶的相互作用下，与 300 μmol·L-1 褪黑素相比，500 μmol·L-1 褪黑素可以更有效地清除 ROS 并减少细胞过氧化。总的来说，500 μmol·L-1 褪黑素的效果优于 300 μmol·L-1。综上所述，褪黑素浸种促进了水分胁迫下大豆种子的萌发。
