Cauliflower Response to Rising Melatonin Doses Under Flooding Stress

Flooding stress is a major abiotic factor that significantly reduces yield and quality in crops. Melatonin (MEL), a bioactive molecule, is known to play a crucial role in mitigating stress-induced damage in plants. This study aimed to investigate the effects of different MEL doses (50, 100, 150 and 200 µM) on agronomic, physiological, and biochemical responses of cauliflower (Brassica oleracea var. botrytis) seedlings under flooding conditions. The results indicated that flooding stress markedly inhibited plant growth and development, significantly reducing parameters such as plant height, fresh and dry weight. Principal component analysis revealed that the first three components explained 85.67% of the total variation, with flooding stress being the dominant source of variability. In this analysis, it was determined that the most important factor is flooding stress. MEL treatments, particularly at 50–150 µM doses, alleviated the negative effects of stress and improved plant growth traits. Biochemical analysis showed a significant increase in reactive oxygen species (ROS) indicators such as malondialdehyde (MDA) and hydrogen peroxide (H2O2) under flooding stress. This was accompanied by enhanced activity of peroxidase (POX), suggesting a strong antioxidative response. Among the antioxidant enzymes, POX played a key role in detoxifying ROS under stress conditions. In conclusion, exogenous MEL applications at moderate doses enhance stress tolerance by improving growth and activating antioxidant defense mechanisms in cauliflower. These findings suggest that MEL could be an effective strategy for improving yield and quality under both normal and stress-induced growing conditions.