Effect of Silicon nutrition on growth and physiology of spearmint (Mentha spicata L.) under Cadmium stress condition

Silicon (Si) is the second most abundant element in the earth crust. Silicon has been shown to ameliorate the adverse effects of heavy metals on plants. In order to investigate the effects of silicon nutrition on tolerance of mint (Mentha spicata L.) to cadmium stress, a factorial experiment based on Completely Randomizad Design was conducted in four replications in research greenhouse of Mohaghegh Ardabili University at 2014-2015. Experimental factors included soil contamination by cadmium (0, 50, 100 and 250 mg/kg soil) and silicon nutrition (0 and 1 mM). The number of pots was 32 also in each pot one spearmint stand were planted. During this experiment, traits such as: plant height, plant dry weight, root and stem dry weight, leaf and stem number, leaf area, chlorophylls index, electrolyte leakage, relative water contents, chlorophylls a, chlorophylls b, total chlorophylls, enzyme activity of peroxidase, polyphenoloxidase, as well as proline, carbohydrates, caretenoids were measured. Results indicated the intractive effects of cd stress and si on plant height, leaf area, plant dry weight, stem dry weight, root wet weight, proline, activity of peroxidase, polyphenoloxidase, chlorophylls a, chlorophylls b, were significant. The highest value for carbohydrate, peroxidase, polyphenoloxidase, chlorophylls a, chlorophylls b, plant height, plant and stem dry weight, leaf area, root wet weight were obtained by foliar spraying of 1 mM concentration of silicon and without cd stress. In general, it can be concluded that foliar spraying of silicon is effective to increase total chlorophylls, plant dry weight, and stem dry weight under cd stress.