Low-temperature stress adversely impairs rice germination and seedling establishment. This study assessed a nano-bio-priming strategy using lecithin (L) and silicon dioxide nanoparticles (SiO2 NPs) to enhance chilling tolerance. Two fragrant rice cultivars (Xiangyaxiangzhan and Meixiangzhan 2) were primed with six combinations of lecithin (0, 50, and 100 μmol·L−1, denoted as L0, L1, and L2) and SiO2 NPs (0 and 100 mg·L−1, denoted as S0 and S1) and exposed to optimal temperature (25 °C) or low-temperature stress (15 °C). Low-temperature stress delayed germination onset by two days. Combined priming treatments L1S1 and L2S1 significantly alleviated this inhibitory effect. Crucially, cultivar-specific responses were evident in Meixiangzhan 2, where L1S1 increased the germination vigor index by 50.97%. Meanwhile, the effect was less pronounced or inhibitory at normal temperature in Xiangyaxiangzhan. Priming substantially enhanced seedling growth, and L2S1 maximally increased root and shoot length in Meixiangzhan 2 by 55.30% and 15.82%, respectively. Furthermore, biomass accumulation was strongly promoted. L1S1 increased total dry weight and total fresh weight in Meixiangzhan 2 by 19.64% and 23.48%, respectively. Physiologically, priming elevated chlorophyll and carotenoid contents upregulated the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), and increased levels of soluble protein and ascorbate (AsA), while maintaining nitrate reductase (NR) activity and hydrogen peroxide (H2O2) homeostasis. These physiological improvements were positively correlated with enhanced growth. Our findings demonstrate that co-priming with lecithin and SiO2 NPs is a potent strategy for enhancing low-temperature tolerance, with efficacy depending on both the treatment combination and rice genotype.
Chen et al. (Mon,) studied this question.