The technology of in vitro plant culture by supplementing classical breeding methods has been widely accepted for genetic modification and plant improvement. The ornamental Kale (Brassica oleracea var. acephala) has considerable attention due to its properties such as colorful aerial parts, durability, and good resistance to adverse environmental conditions. The role of different forms of heavy metals in in vitro culture is still unclear. Therefore, there are conflicting reports including positive and negative effects of these compounds on plant in vitro culture. The purpose of this research was to investigate the effects of lead nitrate [Pb(NO₃)₂], silver nitrate (AgNO₃), and silver nanoparticles (AgNPs) on in vitro cultureof Brassica oleracea var. acephala . This study was conducted in two separate experiments comprising: applying treatments on callus induction and applying treatments on shoot regeneration. Pb(NO₃)₂, AgNO₃ and AgNPs were added at differentiation concentrations (0, 10, 25, and 50 mg L-1) in MS media. The traits such as browning index, pathogen contamination, rooting percentage, callus diameter, callus growth, fresh and dry weight, callus induction, shoot and root regeneration were evaluated after 30 days from the culture. The results indicated the positive effect of heavy metals in both nano and ionic metals forms. It seems that the concentration of silver nanoparticles should be considered lower due to its greater efficiency in stimulating shoot regeneration. However, the achievements of these experiments can be the initial basis for other research in the field of the application of nano forms in plant in vitro culture.
