Dopamine-mediated enhancement of drought resilience and phytonutrient profiling in Brassica oleracea var. sabellica L.

Due to changing climate conditions, drought stress is increasing, leading to significant reductions in agricultural productivity and posing a serious threat to global food security. One of the main reasons for plant growth disruption is drought stress. In recent years, the use of sustainable and eco-friendly compounds to mitigate drought-induced damage has gained attention. Dopamine, a catecholamine neurotransmitter, has emerged as a potential regulator of plant stress responses. This study aimed to investigate the effects of exogenous dopamine on drought stress tolerance in green kale, examining morphological, physiological, and biochemical responses. A factorial experiment was carried out in the form of a completely randomized design with three replications. Two factors were examined: (a) three drought stress levels (100% (control), 50%, and 25% of the field capacity (FC) and (b) three dopamine levels (control (distilled water), 50 and 100 µM). Vegetative traits (plant height and number of leaves), and plant yield of green kale exhibited a significant decrease under drought stress (25% FC). Under 25% FC condition, photosynthetic efficiency (SPAD, Fv/Fm), relative content of water (RWC) and potassium (K) concentration decreased. In contrast indicators of oxidative stress, such as electrolyte leakage (EL), hydrogen peroxide (H 2 O 2 ), malondialdehyde (MDA) increased, alongside the activity of antioxidant enzyme activities (catalase (CAT) and peroxidase (POX)) and phenylalanine ammonia-lyase (PAL). Exogenous dopamine application alleviated drought-induced damage by enhancing antioxidant enzyme activity, proline accumulation, total soluble sugars, total protein, ascorbic acid, RWC, and K content, while reducing MDA and H 2 O 2 levels. Furthermore, dopamine-treated plants under severe drought (25% FC) exhibited the highest concentrations of secondary metabolites, including carotenoids, glucosinolates, and anthocyanins. The results demonstrate that dopamine application enhances drought tolerance in green kale by modulating growth and physiology, thereby mitigating oxidative stress and improving water status and nutrient content. Dopamine alleviates drought stress in green kale by improving photosynthetic efficiency, antioxidant enzyme activities and maintaining ion balance. Additionally, dopamine increased the accumulation of health-promoting phenolic compounds and secondary metabolites under drought conditions there supporting its potential use in biofortification programs. Thus, understanding the role of dopamine in drought tolerance introduces new possibilities to use this compound for agricultural purposes.