Concentration-Dependent Responses of Linseed to Moringa-Mediated Iron Oxide Nanopriming under Early-Season Drought

Abstract

Green-synthesised iron oxide nanoparticles (IONPs) may provide a low-input seed treatment for improving crop establishment under water limitation, but their effects are frequently dose-dependent. This pot experiment evaluated Moringa oleifera-mediated IONP seed priming in linseed (Linum usitatissimum L.) under well-watered and early-season drought conditions. The IONPs were examined by Fourier-transform infrared spectroscopy and vibrating-sample magnetometry. Seeds were untreated, hydroprimed, or primed for 12 h with 50, 100, or 150 ppm IONPs. Treatments were arranged as a 5 x 2 factorial completely randomised design with three replicates. Water regimes were maintained at 75% or 35% field capacity through 50 days after sowing. Drought delayed emergence and reduced chlorophyll index, plant height, tiller number, grain yield, and biological yield. Under drought, 100 and 150 ppm shortened time to 50% emergence by about 18% relative to untreated seed, while 100 ppm produced the highest emergence index (1.02) and final emergence (80%). However, these early benefits did not improve productivity. Hydropriming produced the highest grain yield under both water regimes (0.41 and 0.32 g pot^-1), whereas 150 ppm produced the lowest grain and biological yield under drought (0.23 and 1.36 g pot^-1). Green IONP nanopriming therefore improved early establishment at an intermediate dose but did not recover yield. Dose optimisation, complete particle characterisation, and field validation are required before agronomic recommendation.