Melatonin Concentration and Treatment Technique Influenced the Increase of Cereal Plant Biomass and Antioxidant Defence System Under Salinity Stress. A Meta-Analysis

Abstract

Salinity stress is one of the primary issues with cereal crops (CR) such as corn, rice, and wheat. Melatonin has been shown to enhance CR's growth and physiological activity under salinity stress. Therefore, we performed a meta-analysis to quantitatively evaluate the effect of melatonin treatment (MT) on salinity stress tolerance on growth and physiological activity of CR and to determine the parameters modulated by melatonin. The meta-analysis approach combines all related experiments found in the relevant literature to accomplish this. A total of 325 datasets from 28 published articles were entered into the database. MT used seed priming (SP), water solution (WS), foliar (FOL) and soil drench (SD). Due to the limited number of studies, the melatonin concentration entered in the database was limited to the 0-200 mu M level. Meanwhile, the salinity levels determined in this study ranged from 0 to 51.30 dSm(-1). The analysis was based on a linear mixed model methodology. Different studies were considered random effects, and properties related to melatonin application (either on CR or MT) were treated as fixed effects. Our findings revealed that overall, more significant increases in melatonin concentration were associated with increases in shoot dry biomass (SDB), root dry biomass (RDB), photosynthetic rate (Pn), stomatal conductivity (gs), superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and soluble protein content (SPC) (p < 0.05). The results of the meta-analysis showed that the relationship between CR (maize, rice and wheat) with increased melatonin concentrations resulted in higher increases in SDB, RDB, Pn, SOD, CAT, POD and SPC in corn and higher increases in gs in wheat (p < 0.05). The relationship between MT (SP, WS, FOL, and SD) with an increase in melatonin concentration resulted in a higher increase in SDB and RDB in the SP technique and a higher increase in Pn, gs, SOD, CAT, and POD in the SD technique (p < 0.05). It was concluded that applying melatonin to CR with various types of MT could reduce oxidative damage by increasing the antioxidant defence system and photosynthetic and stomatal activity.