Enhancement of Morpho‐Physiological, Physiological, and Antioxidant Capacity of Saffron ( Crocus sativus L.) Under Water Deficit Using ZnO Nanoparticles and Magnesium Sulfate: Implications for Saffron Yi

ABSTRACT

Water deficit stress is one of the main plant growth and productivity limitation factors. In current study, the Crocus sativus plants were exposed to three irrigation regimes (FC 100%, FC 75%, and FC 25%) combined with ZnO‐NPs (0, 25, and 50 mg L ⁻¹ ) and MgSO ₄ (0, 1.5, and 3 g L ⁻¹ ). Growth, flowering, physiological, and biochemical characteristics were evaluated in a split‐plot experiment based on randomized complete block design (RCBD) with three replicates during 2023–2024. The results demonstrated that severe drought stress markedly reduced leaf dry weight, flower weight, flower number, stigma dry weight, and corm production, while increasing ionic leakage, catalase activity, and proline accumulation. The combined application of ZnO‐NPs and MgSO ₄ improved relative water content, photosynthetic efficiency, antioxidant activity, vegetative growth, and flowering performance under full irrigation and mild water deficit (75% FC) conditions, while under severe drought (25% FC), these treatments especially ZnO‐NPs intensified plant stress. CAT activity and proline content increased considerably in response to ZnO‐NPs 50 mg L ⁻¹  × MgSO ₄ 3 g L ⁻¹ under FC 75% and FC 25%. Application of ZnO‐NPs and MgSO ₄ effectively alleviated drought‐induced damages under moderate irrigation (FC 75%) and enhanced plant tolerance to water stress. Results of PCA and Cluster analysis proved that application of ZnO‐NPs at 50 mg L ⁻¹  + MgSO ₄ 3 g L ⁻¹ provide the most balanced improvement in growth, flowering, and stress tolerance traits under mild drought stress.