Effects of seed priming with different melatonin concentrations on maize seed germination under DS conditions. No priming (NP): unprimed seeds; hydro-priming (HP): primed in water only; no-stress (NS): no PEG-6000 was added; DS: 15% PEG-6000 was added; melatonin-priming (M1): 250 µM melatonin; melatonin-priming (M2): 500 µM melatonin; melatonin-priming (M3): 1000 µM melatonin. Data represent means of all replicates, and the vertical bars are the LSD values based on 0.05% probability values.