Influence of N-Acetylglucosamine and Melatonin Interaction in Modeling the Photosynthetic Component and Metabolomics of Cucumber under Salinity Stress.

The application of N-acetylglucosamine (GlcNAc) and melatonin (Mel) in agriculture could be a promising avenue for improving crop resilience and productivity, especially under challenging environmental conditions. In the current study, we treated the cucumber plant with GlcNAc and Mel solely and combinedly under salt stress (150 mM) then studied photosynthetic attributes using the transient OJIP fluorescence method. The results showed that the combination of GlcNAc × Mel significantly improved the plant morphological attributes, such as root and shoot biomass, and also improved chlorophyll and photosynthetic components. The mineral elements such as K, Mg, Ca, and P were significantly elevated, whereas a lower influx of Na was observed in GlcNAc × Mel treated cucumber shoots. A significant reduction in abscisic acid was observed, which was validated by the reduction in proline content and the increase in stomatal conductance (Gs), transpiration rate (E), and substomatal CO concentration (Ci). Furthermore, the activities of antioxidants such as polyphenol and flavonoid were considerably improved, resulting in a decrease in SOD and CAT with GlcNAc × Mel treatment. In addition, GlcNAc × Mel treatment dropped levels of the toxic radical Malondialdehyde (MDA) and elevated amino acids in cucumber shoots. These findings suggest that the combination of GlcNAc × Mel could be an effective elicitor for modeling plant metabolism to confer stress tolerance in crops.