Mechanisms of growth-promotion and Se-enrichment in Brassica chinensis L. by selenium nanomaterials: beneficial rhizosphere microorganisms, nutrient availability, and photosynthesis

Abstract

Maintaining a suitable selenium (Se) content in food is particularly important for human health. However, the mechanisms of uptake and enrichment of Se ENMs in crops are still unclear. Herein, Se engineered nanomaterials (Se ENMs) (size: 62.3 ± 14.6 nm and surface charge: −34.4 ± 1.4 mV) were synthesized and used as nanofertilizers for Se-fortified vegetables. The results demonstrated that the Se content and yield were increased by 338.0% and 19.8%, respectively, in Brassica chinensis L. through soil application of Se ENMs (0.5 mg kg⁻¹). The Se content in vegetables increased up to 32.8 μg/100 g (7.5 μg/100 g for the control), which could provide the daily recommended Se intake (55–400 μg per day) for humans. Modification of the slightly alkaline soil with the Se ENMs improved beneficial rhizosphere microbiomes (Pseudomonas and Bacillus), which resulted in the plants accumulating more low molecular weight compounds (betaine, proline, glycine, norleucine, urocanic acid and indole-3-acrylic acid) with an increase in the Se content of the plant by 264.9%. Moreover, the nutrient accumulation in leaves promoted photosynthesis (16.7%) and increased the carbohydrate content (6.5%). Also, the expression of carbohydrate transport-related genes (BnSUC1,1, BnSUC1,4, and BnSWEET10,2) was up-regulated 52.2, 53.2 and 76.3-fold, respectively, promoting root growth and improving rhizosphere microbiome and nutrient availability. Therefore, such mutual benefits between leaves and roots using ENMs could provide an alternative model for cultivating Se-enriched crops.