Multi-level evidence of titanium dioxide nanoparticle toxicity in blueberry plantlets

Titanium dioxide nanoparticles (TiO 2 NPs) are increasingly proposed for agricultural applications; however, their crop-specific safety profiles remain insufficiently understood. Here, we provide, to our knowledge, the first integrative evidence that TiO 2 NPs exert predominantly negative effects on blueberry ( Vaccinium corymbosum L.), a high-value woody perennial. In an in vitro 40-day exposure (30, 60, 90, 150 mg L −1 ), we quantified coordinated responses across physiological, histological, and biochemical levels. Shoot elongation declined at all doses (up to 57%), with reduced biomass at higher concentrations. Histological analysis showed progressive tissue disorganization, from mild cell compaction at low doses to necrosis and vascular damage at 150 mg L −1 . Chlorophyll a , chlorophyll b , and carotenoid levels declined by up to 68%, indicating impaired photosynthetic capacity. Concurrently, TiO 2 NPs stimulated antioxidant defenses: phenolic and flavonoid content increased up to threefold, while superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities rose by 138% and 147%, respectively. Correlation and sensitivity analyses confirmed strong antagonism between growth and defense responses. Shoot length positively correlated with pigment content ( r = 0.99) but negatively with SOD ( r = − 0.87) and flavonoids ( r = − 0.75), suggesting a trade-off between growth and oxidative stress mitigation. SOD, APX, and carotenoids emerged as the most responsive biomarkers. Collectively, these multi-level data demonstrate that TiO 2 NPs inhibit development and disrupt tissue integrity in blueberry, supporting a precautionary perspective: TiO 2 NP-based fertilizers are not recommended for blueberry cultivation until safe exposure thresholds are validated under soil and field conditions.