Alleviatory effect of foliar application of silicon nanoparticles on germination, growth, and photosynthetic pigments of Butterfly pea (Clitoria ternatea) under salt stress

Soil salinity substantially limits plant establishment and productivity by reducing germination, altering photosynthetic function, and lowering biomass buildup. This study examined the effect of foliar-applied silicon nanoparticles (SiNPs) on Clitoria ternatea germination, early seedling development, growth performance, and physiological characteristics under graded salinity stress (0, 50, 100, and 150 mM NaCl). Salinity significantly lowered all evaluated characteristics. Compared with the control, exposure to 150 mM NaCl reduced plant height by approximately 51% and leaf area by nearly 55%. Fresh biomass also declined significantly indicating pronounced growth inhibition under severe salinity stress. Foliar application of silicon nanoparticles (SiNPs) markedly alleviated these detrimental effects. Under 150 mM NaCl, SiNP treatment increased plant height by nearly 38% and leaf area by about 24% relative to untreated salt-stressed plants. Likewise, dry biomass improved by approximately 16%, demonstrating the positive regulatory role of SiNPs in mitigating salinity-induced growth suppression. Chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids were all lowered by salinity but improved after SiNP addition, demonstrating Si’s protective effect on pigment stability. Salinity reduced total chlorophyll, carotenoids, chlorophyll a, and chlorophyll b, but this level increased after SiNP was added, indicating the protective effect of silicon nanoparticles on pigment stability. Biochemical responses validated this mitigation: SiNPs improved salinity-induced proline and soluble sugar accumulations while partially reversing protein, phenolic, and flavonoid decreases. PCA analysis validated these findings by categorizing treatments based on biomass accumulation and structural growth, with SiNP-treated plants clustered in the higher-performance quadrants. SiNP foliar spray increases osmotic adjustment, pigment integrity, and vegetative growth under saline circumstances. Silicon nanoparticles thus constitute an effective, feasible, and environmentally safe method for increasing salt tolerance in C. ternatea.