Silica nanoparticles promote the germination of salt-stressed pepper seeds and improve growth and yield of field pepper

Silica nanoparticles (SiNPs) play important roles in mediating plant growth and resistance against biotic/abiotic stresses. However, the underlying mechanisms are still unclear in pepper. Here, the influences of SiNPs on pepper seed germination, as well as on plant growth and yield, were investigated. The results showed that SiNP300 (300 mg/L SiNPs) could significantly improve germination of salt-stressed seeds and increase the germination rate, germination index, and radicle length by 3.8 %, 40.7 %, and 19.4 %, respectively. Further analysis revealed that SiNP300 decreased the activities of peroxidase, catalase, superoxide dismutase, the contents of malondialdehyde (MDA), protein, proline (Pro), H2O2, and O-2(center dot-) of salt-stressed pepper seeds. Meanwhile, Schiff and Evans blue staining analysis showed that SiNP300 could reduce lipid peroxidation and improve plasma membrane integrity of salt-stressed pepper plumule. Under field condition, SiNP300 treatment increased the germination rate, growth and development, net photosynthetic rate, and yield per plant. Moreover, SiNP300 could increase leaves cytokinin, auxin, and abscisic acid contents by 1.66-fold, 2.27-fold, and 20.8-fold, which potentially contribute to the promoted pepper growth and yield in field. Besides, SiNP300 increased the activity of peroxidase and decreased the activities of catalase and superoxide dismutase in the leaves and decreased the activities of POD, CAT, and SOD in the roots, which may better maintain the balance of defense response and growth in field. This study indicates that SiNP300 promote the germination of salt-stressed pepper seeds and improve the growth and yield of pepper in the field, which established theoretical basis for the potential utilization of SiNPs in agricultural practices.