Improvement of physio-biochemical attributes and mitigation of salinity stress by combined application of melatonin and silicon nanoparticles in Brassica oleracea var. botrytis

•Brassica oleracea var. botrytis experienced stunted growth when grown in saline soil.•Applying Silicon nanoparticles (Si-NPs) and melatonin (MT) mitigated the salt stress effects, improving the growth and raising chlorophyll contents.•Combined treatment of MT and Si-NPs might be effective against salt stress in B. oleracea.