Impact of one- and two-component matrixless metal nanoparticle systems on the growth and chemical composition of lettuce (Lactuca sativa)

Metal nanoparticles (NPs) are increasingly recognized as potential biostimulants capable of improving plant growth and nutritional value in modern horticulture. However, conventional nanoparticle formulations often contain organic stabilizers that can impair the true biological effects of the metals. To address this, our study evaluated the impact of matrixless (i.e., lacking any organic stabilizers or other additives) metal nanoparticle formulations on the growth and chemical composition of Lactuca sativa L. var. capitata . Foliar application of 5 mg/L silver nanoparticles (AgNPs) significantly stimulated plant development, most notably increasing L-ascorbic acid content by 68.6%, chlorophyll index by 47.0%, and nitrogen balance index by 40.2%. Significant improvements were also observed in leaf surface area (35.2%), fresh mass yield (22.1%), anthocyanin index (13.7%), flavonol index (4.6%), and dry matter content (3.3%). Moreover, AgNPs treatment led to a significant decrease in Cu levels in plants, likely due to competitive uptake mechanisms. The results showed that the highest NPs concentrations were found within the roots, with leaves showing lower accumulation. Overall, the results suggest that the matrixless metal NPs, particularly silver-based ones, have great potential for enhancing plant growth and nutritional value at the low concentrations of examined systems.