Pre-treatment of melatonin enhances the seed germination responses and physiological mechanisms of soybean (Glycine max L.) under abiotic stresses

Abstract

The germination of soybean (Glycine max L.) seeds is critically affected by abiotic stresses which resulting in decreasing crop growth and yield. However; little is known about the physiological mechanisms of germination and the potential role of melatonin on soybean seed germination under drought, salt, cold, and heat stresses. Therefore, the current study investigated the possible effects of melatonin to enhance germination indices and other physiological attributes by alleviating the harmful impacts of these stresses during germination. Seeds of soybean were pre-treated (seed priming) with melatonin at MT1 (20 μmol L-1), MT2 (50 μmol L-1), MT3 (100 μmol L-1), MT4 (200 μmol L-1), and MT5 (300 μmol L-1) and exposed to the four stresses (drought at PEG 15%, salt at 150mM, cold at 10 °C, and heat at 30 °C) . It was noted that MT1 (20 μmol L-1), MT2 (50 μmol L-1), and MT3 (100 μmol L-1) remarkably improved the germination potential, germination rate, radical length, and biomass under given stresses. Furthermore, MT1, MT2, and MT3 progressively increased the proline to minimize the impact of drought, salt, cold, and heat stresses. In addition, all stresses significantly induced oxidative damage however, salt (150 mM NaCl) and heat (30 °C) stresses highly increased the malondialdehyde content (MDA) and hydrogen peroxide (H2O2) as compared to drought (PEG 15%) and cold (10 °C) stresses. Moreover, MT2 and MT3 significantly enhanced the activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) to reduce the oxidative damage in soybean seeds during the germination. Overall, melatonin at 50 μmol L-1 and 100 μmol L-1 considerably mitigated the harmful impacts of drought, salt, cold, and heat stress by enhancing germination and other physiological mechanisms of soybean. This study could provide bases to enhance the melatonin-mediated tolerance of soybean and other related crops at early growth stages when exposed to abiotic stresses.

Melatonin as a key regulator in seed germination under abiotic stress

“…Third, MEL can be pro‐oxidant at higher dose and can induce oxidative changes in protein and amino acids, 201 while MEL also positively regulates the internal ROS levels in seeds which are crucial to stimulate the breakage of SD and initiation of SG under stressful conditions 202,203 . Several other convincing reports also supported the inhibitory effects of MEL at high concentrations on SG and seedling growth 87,102,160,188,204 …”

“…The MEL application improved SG by increasing the activities of AO and accumulation of soluble proteins in seeds 154 . Moreover, MEL improved the viability and germination ratio of pollen grains, 157 which could be associated with higher accumulation of soluble proteins, vitamin C and AO, 158 higher GAs biosynthesis, 159 and regulation of redox network 160 . The imposition of HT stress during reproductive seed filling stage reduces seed quality and vigor, which later influences SG 161,162 associated with reduced starch, amylose, and amylopectin contents in seeds 163,164 .…”

“…202,203 Several other convincing reports also supported the inhibitory effects of MEL at high concentrations on SG and seedling growth. 87,102,160,188,204…”

“…154 Moreover, MEL improved the viability and germination ratio of pollen grains, 157 which could be associated with higher accumulation of soluble proteins, vitamin C and AO, 158 higher GAs biosynthesis, 159 and regulation of redox network. 160 The imposition of HT stress during reproductive seed filling stage reduces seed quality and vigor, which later influences SG 161,162 associated with reduced starch, amylose, and amylopectin contents in seeds. 163,164 MEL application prolonged seed viability (based on tetrazolium test) after exposure to HT due to its role in improving seed quality, 164 and antioxidative properties.…”

Improving germination and quality of soybean seeds by using natural compounds

“…Soybean (Glycine max L.) is an essential crop globally. Soybean seeds have a cholesterol-free oil content of 18 to 22%, 85% unsaturated fatty acids, and 38 to 42% protein (Ali et al, 2009;Awan et al, 2023). Using high-quality seeds is one way to increase soybean production.…”