Effects of foliar and root application of Zn and Fe bio-nanofertilizers on the glucosinolate, Zn and Fe contents of Pak choi (Brassica rapa Subsp. Chinensis) grown under hydroponic and pot cultivation

• ZnO and γ-Fe 2 O 3 NPs treated with A. platensis extract constitute novel bio-nanofertilizers for Pak choi. • Combination of Zn and Fe NPs with alga extracts was examined for the first time on the enhancement of GSLs, Zn and Fe contents of Pak choi. • Foliar fertilization with algae capped ZnO and γ-Fe 2 O 3 NPs exerted the best results to improve growth and Zn and Fe contents in hydroponic and pot-cultivated plants. • The joint application of NPs and microalgae extract enhanced the GSLs contents. • The organic and inorganic components in the bio-nanofertilizers presented a synergistic interaction. Pak choi is a rich source of minerals and health beneficial compounds such as glucosinolates (GSLs). This study is focused on implementing sustainable agronomic approaches to optimize pre-harvest cultivation and improve plant growth and nutritional value. Therefore, the aim of this work was to evaluate the effect of foliar and root fertilization of algae capped ZnO and γ-Fe 2 O 3 nanoparticles on the growth and content of GSLs, Zn and Fe of Pak choi grown under hydroponic floating system and pot conditions. The foliar application of ZnO (77 nm) and γ-Fe 2 O 3 (68 nm) nanoparticles functionalized with an Arthrospira platensis extract increased fresh weight (39.71 %), plant height (42.77 %), leaves number (26.47 %), root length (33.33 %), and Zn (10-fold) and Fe (2-fold) contents in hydroponic plants. The same treatment also improved plant fresh weight (31.73 %), and Zn (6-fold) and Fe (2-fold) in pot cultivated Pak choi. Six GSLs were detected, which were also enhanced by the joint application of nanoparticles and microalgae extract. The results revealed a high synergy between the ZnO- and γ-Fe 2 O 3 nanoparticles and the A. platensis extract to increase plant growth and Zn and Fe micronutrients and glucosinolates in Pak choi grown under hydroponic and pot systems.