Silicon Titanium Oxide Nanoparticles Can Stimulate Plant Growth and the Photosynthetic Pigments on Lettuce Crop

Our knowledge of the bioactivity of silicon titanium oxide nanoparticles (TiSiO₄ NPs) in crops is scarce, contrarily to TiO₂NPs and SiO₂NPs that are used in many industrial sectors, and have emerged in nanoagriculture (e.g., as pesticides or nanofertilisers). To evaluate the potential of using TiSiO₄ NPs in nanoagriculture, it is necessary to characterize their potential benefits on crops and the safety doses. Here, we report for the first time the bioactivity of TiSiO₄ NPs (up to 100 mg/L) in the model crop lettuce (Lactuca sativa L.) exposed for three weeks (from seeds/seedlings to pre-harvesting phase). The doses applied did not compromise the germination rate, and highly stimulated plant fresh matter. TiSiO₄ NPs had beneficial effects on photochemical processes by increasing chlorophyll levels. Effects on photosynthesis are less evident but TiSiO₄ NPs (100 mg/L) stimulated the photosynthetic potential, increasing F_v/F_m and ETR when compared to the 50 mg/L conditions. TiSiO₄ NPs did not influence the net photosynthetic rate and other Calvin-cycle variables. Soluble sugars and starch levels were overall maintained. In general, this first report on TiSiO₄ NPs bioactivity suggests that they did not have a toxic effect, and may be used to potentiate crops’ growth. Principal component analysis (PCA) also shows that despite effects on photosynthetic performance is minimal regarding the control, the 50 and 100 mg/L doses strongly differ, with the lower dose promoting mostly pigment accumulation, while the higher dose slightly stimulates Photosystem II efficiency including the electron transport rate and other gas exchange parameters.