Evaluation of the effects of silicon nutrition on alleviation of iron deficiency in rice plants (Oriza sativa L.) with emphasis on growth and antioxidant enzymes activity

Iron is an essential element in all plants and its deficiency causes drastic growth retardation. Silicon is also an essential element in Poaceae family including rice that may reduce biotic and abiotic stresses in plants. In this research, the interactions of silicon and iron nutrition were studied in rice (Oryza sativa L. cv. Tarem). The plants cultivated in greenhouse under iron treatments of 0, 2 and 10 mg l-1 as a Fe-EDTA and silicon treatments of 0 and 1.5 mM as a sodium silicate. The expeiment was teriminated after 3 weeks of iron treatments and then the plants were harvested for assying growth and biochemical factors. Iron deficiency resulted in reduction of fresh mass, contents of chlorophyll, carotenoides and iron in shoots. In addition, the activity of catalase, cell wall and soluble guaiacol peroxidase, and polyphenol oxidase in shoots decreased under iron deficiency. As a result, the amount of hydrogen peroxide in roots and lipide peroxidation in shoots increased due to iron deficiency. Silicon nutrition, however, increased the iron content and recovered the fresh mass, chlorophyll and carotenoides contents as well. The effects of silicon application and optimal iron nutrition on plant growth were synergetic. Silicon nutrition caused significant increase in the cell wall and soluble guaiacol peroxidase activity in both roots and shoots and the catalytic activity in shoots. Consequently, the hydrogen peroxide in roots and the lipide peroxidation in shoots decreased following silicon application. The results indicated that silicon application could alivatie the harmful effects of iron deficiency in vegetative growth stage in rice.