Response of Spinach Plants to Different Doses of Two Commercial Nanofertilizers

The use of nanofertilizers could be a potential solution to address the current challenges of agriculture (global hunger, increase of world population, highly inefficient use of fertilizer, soil nutrient deficiency and scarcity of raw materials). Most available literature focuses on the effects of some nanomaterials synthesized at lab scale and detailed information about commercial nanofertilizer is lacking. The aim of the present study was to characterize two commercial nanofertilizers (NF-A and NF-B) and evaluate the effect of their foliar application at increasing doses (recommended dose (RD), 10RD, 100RD and 500RD) on spinach plants. Both nanofertilizers differed greatly in composition, colloidal stability and morphology. Their impact on spinach leaves depended on nanofertilizer composition and dose and they did not have negative effects at the recommended dose or at 10RD. However, NF-B at the highest doses (100RD and 500RD) had major negative effects on leaves compared to NF-A and induced a reduction in the content of chlorophyll, polyphenols, flavonols and antioxidant activity, an increase in oxidative damage, and the deterioration of the cellular ultrastructure according to TEM analysis. In contrast, leaves treated with NF-A showed few changes and only at the highest dose (500RD) were some adverse effects detected. Foliar application of the two commercial nanofertilizers modified the surface composition as well as the nutrient content of the leaves, adding new elements and increasing the content of others, especially at the highest doses tested. The present study will contribute to the establishment of safe levels of nanofertilizer exposure and provides a starting point for studies on the mechanisms involved in nanoparticle uptake by leaves.