Facilitation of iron and potassium uptake and decrease of calcium and magnesium absorption by silicon nutrition in rice plants

Silicon as an essential nutrient in rice plant affects many growth factors including yield. The main object of this study was to evaluate the effects of silicon application on growth, uptake pathways and accumulation of some nutrients and phenolics and lignin contents in rice plant, Oryza sativa cv. Fajr. The plants cultivated in Hydroponic culture medium with Yoshida nutrients in growth chamber under controlled condition. Silicon treatments were included two 0 and 1.5 mM sodium silicate. The plants treated with silicon for 12 days indicated higher fresh and dry weight of shoot, relative growth rate and shoot to root ratio compared to plants devoid of silicon nutrition. In contrast, transpiration was decreased significantly due to silicon application. Also, uptake and accumulation of silicon, iron and potassium were significantly increased and calcium and magnesium uptake and accumulation were markedly decreased following silicon application. Soluble phenolics significantly decreased in roots and shoots of silicon treated plants, while lignin increased in root and decreased in shoot due to silicon application that may related to creation of barrier in apoplastic pathway of nutrients uptake. Measurement of nutrients uptake by reduction of their concentration in nutrient solution following different treatments including 2,4-Dinitrophenol, sodium cyanide and cold in roots environment and saturation of water vapor in shoots indicated that probably silicon deposition in cell wall and vascular space limited apoplastic uptake of calcium. On the other hand, improvement of membranes function increased iron uptake via intracellular pathway.