Exogenous melatonin reduces the inhibitory effect of osmotic stress on antioxidant properties and cell ultrastructure at germination stage of soybean

Abstract

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.

The mechanisms underlying melatonin improved soybean seedling growth at different nitrogen levels

“…In addition, melatonin can function a an antioxidant capacity. In recent years, melatonin has been widely used as a protective agent against multiple stresses including unfavourable salt concentrations, ultraviolet radiation, toxic chemicals, extreme temperature, osmotic stress, pathogen infection, and nutritional defects (Zhang et al 2017a;Fan et al 2018;Bawa et al 2020;Mohamed et al 2020;Zhang et al 2020). Under abiotic stress including drought, the alleviation effect of melatonin on plant growth may also be attributed to its regulation of carbon and nitrogen metabolism (Cao et al 2019;Zou et al 2020).…”

Melatonin treatment improves postharvest quality and regulates reactive oxygen species metabolism in “Feizixiao” litchi based on principal component analysis

“…On the other hand, the antioxidant-related enzymes, such as SOD, CAT, APX, and GR, constitute an enzymatic antioxidant system in plants. Melatonin has been shown to effectively increase the activities of enzymes related to the oxidative defenses in apple ( Sun et al, 2021a ), maize ( Malik et al, 2021 ), strawberry ( Wu et al, 2021 ), and soybean ( Zhang et al, 2020 ). The exogenous melatonin treatment also increased the endogenous melatonin accumulation in the litchi samples during storage ( Hu et al, 2018 ; Ze et al, 2021 ).…”

Enhanced total flavonoid accumulation and alleviated growth inhibition of germinating soybeans by GABA under UV-B stress

“…The intracellular free calcium was measured using the method of Cheng et al 29 The H 2 O 2 and O 2 ˙ − fluorescence staining we referred to the method of Zhang et al 30 Soybean root tips were washed with deionized water and cut to 3 mm length in 300 μL of HBSS staining solution (containing 0.02% Pluronic F-127, 10 μM Fluo-4AM, pH 7.2) and incubate in the dark at 4 °C for 2 h, then wash three times with hanks balanced salt buffer solution (HBSS) and incubate in the dark at 25 °C for 2 h. The incubated samples were placed on dry slides and observed using an LSM 880 NLO confocal laser scanning microscope (Leica Excitation Technology Co., Ltd., Germany).…”