Selenium nanoparticles as a rooting agent of rice plants to tolerate low phosphate stress

Nanoparticles offer promising applications in agriculture due to their unique physicochemical properties. This study investigated selenium nanoparticles (SeNPs) as a rooting agent to improve rice tolerance to low phosphate stress. IR64 rice was grown in media with varying SeNP concentrations (0-25 ppm), and plants were analyzed at 2 and 6 weeks for phenotypic traits, histology, biochemistry, and gene expression. At 2 weeks, 25 ppm SeNPs led to a threefold increase in root length versus untreated controls. Histological analysis revealed increased root perimeter and diameter, along with reduced aerenchyma perimeter. After 6 weeks under phosphate starvation, SeNP-treated plants showed higher phosphate and selenium content in roots and shoots, increased shoot length and weight, and reduced root length, weight, and phenolic content. Gene expression analysis showed that SeNPs upregulated key phosphate deficiency response genes, including OsPAP21, OsPT9, OsSPX, and OsPHR2. The most dramatic change was observed in OsSPX expression, which increased nearly 250-fold in shoots under full phosphate conditions. This is the first study to demonstrate that SeNPs promote root growth, enhance phosphate uptake, and regulate gene expression, suggesting SeNPs may serve as a sustainable strategy to boost phosphate use efficiency in rice cultivation.