Chloroplast dysfunction under engineered nanoparticle stress: consequences for photosynthesis and plant growth

Annual production of engineered nanoparticles (ENPs) now exceeds thousands of metric tons because of their expanding applications in agriculture, waste management, and environmental technologies. This review provides a mechanistically integrated synthesis of ENP-induced chloroplast dysfunction and its downstream consequences for photosynthesis, plant growth, and reproduction. A bibliometric analysis of 239 publications (1983-2026) highlights a critical gap between primary empirical studies and integrative reviews, establishing a strong rationale for the present work. At the cellular level, the chloroplast is a central target of ENP toxicity within the broader context of whole-plant stress responses. Within the photosynthetic machinery, Photosystem II (PSII) is vulnerable; dissolved metal ions disrupt the Mn₄CaO₅ oxygen-evolving complex, while reactive oxygen species (ROS) accelerate D1 protein degradation and impair the PSII repair cycle. Under phytotoxic exposure conditions, ENP treatment is frequently associated with reduced Fv/Fm, impaired electron transport, and lower net photosynthetic rates. Furthermore, photosynthetic pigment content declines across species, impairing light harvesting and photoprotection. RuBisCO activity may be impaired through oxidative modification and, for some ENP types, through particle- or ion-associated effects on redox-sensitive protein residues. Transcriptomic analyses reveal coordinated downregulation of photosynthesis-associated genes, such as LHCB2.4 and chlorophyll biosynthesis loci, alongside miRNA-mediated post-transcriptional reprogramming. Integrated across the whole plant, these molecular disruptions culminate in biomass reductions, delayed flowering, and impaired germination. This review critically highlights the detrimental effects of high ENP doses on plant health and associated risks for agricultural productivity.