Marigold (Calendula officinalis L.), or Calendula, is an annual plant belonging to the family Asteraceae, has been used historically for medicinal purposes [1]. Seed oil from calendula contains 59-65% calendic acid, which has value in cosmetic, paint, and coating industries. Developing the best management practices for the production of calendula is necessary for optimized yield and profit for growers. Nanoscience coupled with nanotechnology is one of the most important emerging tools which can complement modern agriculture by providing new agrochemical agents and new delivery mechanisms to improve crop productivity. Silicon (Si) is the second most abundant element in the soil; however, it is not considered an essential element. Silicon nanoparticles have been implicated in crop improvement s. The seed germination is an important stage in the higher plant life cycle with respect to its survival. In this research, the influence of different concentrations (0, 0.5, 1.0, 1.5 and 2.0 mg/L) of silicon (source: sodium metasilicate) and silicon nanoparticles (0, 50, 100, 200, and 500 mg/L) on seed germination parameters including germination percentage (GP), mean germination time (MGT), germination rate (GR), root length (RL), shoot length (SL), and seedling vigor index (SVI) of C. officinalis were evaluated under in vitro conditions in a factorial experiment based on completely randomized design with four replications. Based on the ANOVA and analysis of mean (ANOM), seeds exposed to nano-sized silicon showed maximum GP and GI at 50 mg/L. However, the highest RL was obtained at 100 mg/L nano silicon treatment. There were no significant effects among the other examined traits. Moreover, application of silicon (at 0.5 mg/L) caused increase in RL and SL parameters, whereas the maximum GI was observed at 2.0 mg/L silicon exposure. Our findings revealed that seed priming with silicon and nanosilicon at low concentrations may improve germination features of C. officinalis. Nanom
