Effect of selenium supplementation on mycorrhizal onion ( Allium cepa L.) plants

ABSTRACT Selenium (Se) is a beneficial element for higher plants; however, its involvement in improving the plants availability to soil nutrients has not been adequately addressed. Onion ( Allium cepa L.) plants were grown under the sufficient (2 mM) and deficient (0.05 mM) phosphorus (P) supply and inoculated with an arbuscular mycorrhizal fungus (AMF, Diversispora versiformis ) in the absence or presence of 20 or 80 µg Se L –1 applied as Na 2 SeO 4 under greenhouse conditions. Phosphorus deficiency impaired both shoot and root growth, while mycorrhisation increased plants biomass and root length by up to two times, accompanied by increased potassium uptake, levels of non‐structural carbohydrates, protein and amino acids in the leaves and roots. AMF’s impact on biomass production was enhanced by Se supplementation, and the rates of photosynthesis and nitrogen assimilation were also boosted. Besides, AMF effects on the root activity of phosphatase, the acidification of rhizosphere and the mobilisation of insoluble P in the substrate were significantly exacerbated by Se. Our results showed a strong synergistic effect between Se and AMF in improving the plants performance on P‐impoverished soils via enhanced ability to solubilise non‐labile P fractions in the substrate and stimulation of carbon and nitrogen metabolism.