Exogenous melatonin accelerates seed germination in cotton (Gossypium hirsutum L.)

Abstract

Seed germination is considered the beginning of the spermatophyte lifecycle, and it is a crucial stage in determining subsequent plant growth and development. Although many previous studies have found that melatonin can promote seed germination, the role of melatonin in cotton germination remains unexamined. The main objective of this study is the characterization of potential promotional effects of melatonin (at doses of 0, 10, 20, 50, 100 and 200 μM) on cotton seed germination. This experiment demonstrated that low concentrations of melatonin can promote germination, while high concentrations failed to promote germination and even inhibited germination. Together, these results indicate that a 20 μM melatonin treatment optimally promotes cotton seed germination. Compared with the control, germination potential (GP), germination rate (GR), and final fresh weight (FW) increased by 16.67%, 12.30%, and 4.81%, respectively. Although low concentrations of melatonin showed some improvement in vigor index (VI), germination index (GI), and mean germination time (MGT), these effects were not statistically significant. Antioxidant enzyme activity during seed germination was most prominent under the 20 μM melatonin treatment. Superoxide dismutase (SOD) and peroxidase (POD) activities were significantly increased by 10.37–59.73% and 17.79–47.68%, respectively, compared to the melatonin-free control. Malondialdehyde (MDA) content was reduced by 16.73–40.33%. Two important plant hormones in seed germination, abscisic acid (ABA) and gibberellins (GAs), were also studied. As melatonin concentration increased, ABA content in seeds decreased first and then increased, and GA 3 content showed a diametrically opposite trend, in which the 20 μM melatonin treatment was optimal. The 20 μM melatonin treatment reduced ABA content in seeds by 42.13–51.68%, while the 20 μM melatonin treatment increased GA 3 content in seeds to about 1.7–2.5 times that of seeds germinated without melatonin. This study provides new evidence suggesting that low concentrations of melatonin can promote cotton seed germination by increasing the activity of antioxidant enzymes, thereby reducing the accumulation of MDA and regulating plant hormones. This has clear applications for improving the germination rate of cotton seeds using melatonin.

Melatonin improves the germination rate of cotton seeds under drought stress by opening pores in the seed coat

“…To inhibit excessive generation of ROS, plants possess a complex enzymatic defense system to combat oxidative damage (Souza et al, 2014;Ahammed et al, 2020c). SOD and POD act as important antioxidant enzymes that can eliminate redundant ROS from plant tissues, protecting the plasma membrane from peroxidation (Xiao et al, 2019;Ramachandra et al, 2004). In plant cells, SOD can rapidly convert O 2 − to form H 2 O 2 and O 2 , while H 2 O 2 can be further scavenged by other antioxidant enzymes .…”

“…The accumulation of ROS induces lipid peroxidation and the degradation of unsaturated fatty acids, producing MDA, which causes damage to the seed structure and reduces seed germination (Rajjou & Debeaujon, 2008;Xiao et al, 2019). Previous studies have shown that the application of exogenous MT significantly suppressed MDA accumulation under abiotic stressors in several plant species (Ahammed et al, 2019b;Hasan et al, 2019).…”

“…Germination is a complex process regulated by a series of physical and metabolic events in the life cycle of plants (Leónie & Maarten, 2008;Xiao et al, 2019). As the initial stage of plant life cycles and the critical stage of seedling establishment, seed germination is extremely sensitive to drought stress (Ibrahim, 2016).…”

“…A previous study has shown that the mechanical barrier provided by the seed coat increases under stress conditions, indicating that drought stress inhibits seed germination (Debeaujon, Léon-Kloosterziel & Koornneef, 2000). Drought stress leads to the over-production of reactive oxygen species (ROS) in plant cells, which in turn triggers oxidative damage and may lead to cell death (Farooq et al, 2009b;Nahar et al, 2015;Xiao et al, 2019). However, plants have evolved efficient antioxidative defense mechanisms, including the activities of antioxidant enzymes and the regulation of non-enzymatic antioxidants to reduce ROS induced oxidative damages (Posmyk et al, 2009).…”

Fine root and root hair morphology of cotton under drought stress revealed with RhizoPot

“…Cotton is the world's second-most important oil crop and a crucial textile fibre crop (Xiao et al, 2019). The formation of crop yield is a complex process of the interaction between source and sink (Chen et al, 2019), and the morphological and physiological characteristics of the roots are closely related to the growth and development of the aboveground parts (Niu et al, 2018).…”