Title : Melatonin as promoter of germination and development in soybean seeds under to osmotic stress
S oybean (Glycinemax (L.) Merrill) is one of the world’s major oil crops. The productive potential of the soybean crop can be impaired since the seeds are susceptible to several factors during the production process, with water deficiency a limiting factor. Studies suggest that plants can be prepared through specific chemical compounds, termed “priming” to be tolerant to different abiotic stresses. The use of “priming” is a promising field for the physiology of stress in plants, among them we find Melatonin. Melatonin (N-acetyl-5-methoxytryptamine) can alleviate the harmful effects caused by stress and increase its productive potential. Melatonin (MEL) acts in the process of reproduction, germination and growth, and promotion of primary and secondary rooting structures. The aim of this work was to analyze the effect of the exogenous application of melatonin on the initial development of the seedlings and protective action in soybean seeds under osmotic stress. The exogenous application was made of the MEL bioregulator at the dose of 10 μM in soybean cv. Intact under two osmotic conditions, with and without osmotic stress. The germination occurred under the osmotic potential of -1.0 MPa and the hydrated control treatment was established with distilled water (osmotic potential of 0 MPa), and the stress control with mannitol solution (osmotic potential of - 1.0 MPa). Were performed germination test and initial seedling development analysis. The data were analyzed by analysis of variance and the means compared by the Tukey test (p <0.05). For the treatments without conditions of osmotic stress, the application of Mel at the dose of 10 μM presented increase in all parameters evaluated. For the treatments with osmotic stress (-1.0 MPa), the application of Mel presented positive values for all the analyzed parameters, with increase of 6.20% G (germinated), 48.88% GSI (germination speed index), 188% PR5 (root protrusion with 5 days), 16.20% PR8 (root protrusion with 8 day), 12.27% SNS (strong normal seedlings) and 26.17% WNS (weak normal seedlings) when compared to the stressed control. The action of Mel as priming occurs in gene expression in stress situations, as it is also related to the induction of genes involved in cell division and osmoprotective mechanism. These effects can be achieved by activating DNA replication and cell division related to specific genes. The Mel promotes the repair of DNA machinery, resulting in the activation of respiration and the production of ATP during the soaking stage of soybean seeds. The exogenous application of Mel in seeds stimulates the production of signaling molecules and transcription factors that are inactive. Causing a quick defense response when exposed to stress. Thus, Mel is indicated as an osmotic stress attenuator during germination and initial development of soybean seedlings.