Exogenous proline enhances growth, mineral uptake, antioxidant defense, and reduces cadmium-induced oxidative damage in young date palm (Phoenix dactylifera L.)

• Cadmium stress induced depression of plant growth, mineral imbalances and oxidative damage.
• Exogenous proline improved mineral nutrition, enzymatic and non enzymatic antioxidant systems.
• Exogenous proline counteract cadmium inhibitory effects in young date palm plants.

The aim of this study was to investigate the effects of cadmium stress on growth and physiological traits in young date palms and to evaluate the role of exogenous proline in cadmium stress alleviation. Two-year-old date palm plants were subjected for five months to different cadmium stress levels (10 and 30 mg CdCl2 kg−1 soil) supplied or not with exogenous proline (20 mM) through irrigation water. Cadmium stress caused a decline in growth, macronutrient contents (Ca2+, Mg2+, and K+), membrane stability index (MSI), starch content and guaiacol peroxidase (POD) activity. In contrast, an increase of H2O2, soluble sugar, ascorbate peroxidase (APX) activity as well as total polyphenols was observed. Interestingly, exogenous proline effectively mitigated the adverse effects of cadmium on young date palms. Indeed, Cd accumulation was decreased and antioxidant defense systems were significantly (p ≤ 0.05) activated in date palm leaves and roots. Consequently, growth and mineral nutrition were enhanced when proline was added to Cd stressed plants.