Optimization of seed germination in an Iranian serpentine endemic, Fortuynia garcinii

Fortuynia garcinii (Brassicaceae) is endemic to serpentine soils in central Iran. It has indehiscent silicles. The effects of its fruit pericarp on seed imbibition and germination were determined. The effects of moist chilling (15 days) and gibberellic acid (GA₃, four levels), both alone and combined, were also investigated. In addition, the effects of nickel (Ni) on germination and early seedling growth were evaluated. When inside the indehiscent silicles, imbibition of seeds was hampered and germination completely inhibited. Immediately after removing the pericarp, the seeds were able to imbibe as good as isolated seeds, but their germination rates were significantly lower when the removed pericarps were included in the Petri dishes. All the GA₃ concentrations, moist chilling, both alone and combined, significantly shortened mean germination time (MGT), and increased the germination index (GI) and the germination percentage (GP). Excess Ni did not affect GP, but inhibited seedling growth. In conclusion, the pericarp inhibits seed germination, both chemically and mechanically, through impeding imbibition, in F. garcinii. Moist chilling or GA₃ improves the speed and final percentage of germination. Seedling growth is much more sensitive to Ni excess than seed germination.