Silicon, as a beneficial element, can improve the growth and morphological characteristics of the plants propagated by tissue culture. The aim of this study was to investigate the effect of silicon treatment on thornless blackberry (Rubus fruticosus, Merton cultivar) in two phases comprising adventitious root induction and adaption stages. Based on statistical analysis, the experiments in in vitro phase were done at two concentration levels of silicon, i.e., 0 and 1 mg.L−1 while the adaptation stage was comprised of four concentration levels, i.e., 0, 10, 50, and 100 mg.L−1. The results showed that the highest total chlorophyll and carotenoid content were found in the plants treated by silicon at a concentration of 1 mg.L−1 in in vitro phase and 100 mg.L−1 in adaptation stage. Moreover, the same previous in vitro condition along with a silicon-free adaptation stage led to the highest antioxidant activity. The maximum plant height was obtained by silicon treatment at a concentration of 50 mg.L−1 in adaptation stage while in vitro phase was completed in a silicon-free medium. Furthermore, the largest concentration of leaf nitrogen was obtained in the treatment with 1 mg.L−1 and 50 mg.L−1 silicon in in vitro phase and adaptation stage, respectively. The highest concentration of leaf phosphorus was also observed in the plants treated in a silicon-free in vitro phase and an adaptation stage with 50 mg.L−1 silicon. Besides, the same previous condition resulted in the highest concentration of potassium. Finally, the maximum quantum yield of photosystem II (Fv/Fm) was numerically observed in the treatment with 1 mg.L−1 and 100 mg.L−1 silicon in in vitro phase and adaptation stage, respectively.
