Abstract
Shallot (Allium hirtifolium Boiss.) is of considerable nutritional and medical significance due to its strong antioxidant properties; however, no nanophytotoxicity studies have assessed whether the use of nanofertilizers would improve shallot performance, micronutrient iron (Fe) enrichment, and yield in semi-arid regions. Herein, we evaluated the effects of magnetite nanoparticles (nFe(3)O(4)) on shallot grown for a full lifecycle in two semi-arid regions through bulb-priming followed by foliar application and compared them with conventional ferrous sulfate (FeSO(4)) fertilizer and untreated control. Our results showed remarkable cellular adaptations to semi-arid climate upon nFe(3)O(4) treatment as leaves displayed thickened cell walls, distinct chloroplasts featuring organized thylakoid grana and stroma, normal mitochondria, abundant starch grains, and plastoglobuli around chloroplasts compared to FeSO(4) or untreated control. At 900 mg/L nFe(3)O(4), chlorophyll-a, chlorophyll-b, and carotenoid increased by 27-55%, 108-126%, and 77-97%, respectively, compared to FeSO(4) applied at recommended field rate (1800 mg/L). Significant increments in bulb diameter (38-39%) and sister bulb number (300-500%) were observed upon 900 mg/L nFe(3)O(4) treatment compared to FeSO(4) (1800 mg/L) and control. Furthermore, with 900 mg/L nFe(3)O(4) treatment, total phenol, flavonoids, and Fe in bulbs increased by 27-46%, 29-73%, and 486-549%, respectively, compared to FeSO(4) (1800 mg/L). These findings demonstrate that bulb-priming followed by foliar application of 900 mg/L of nFe(3)O(4) could significantly promote cellular adaptation, thereby improving photosynthetic efficiency, bulb yield, antioxidant activities, and Fe biofortification in shallot, and may serve as a novel approach for improving shallot production in semi-arid regions.