Estresse oxidativo em sementes de arroz tratadas com dietholate, silício e submetidas ao frio e ao déficit hídrico

Abstract

Dietholate can inhibit antioxidant enzymes such as superoxide dismutase (SOD) and catalase (POD) that are important in cellular detoxification of excess reactive oxygen forms caused by abiotic or biotic stresses, This is an undesirable effect on the plant. The Silicon (Si) is an enzyme stimulator and can interfere with plant growth and development by promoting signaling for the production of antioxidant compounds (SOD, POD). In this sense, the objective of this study was to evaluate the effect of Si on the reduction of oxidative stress in rice seeds treated with dietholate and subjected to cold and water deficit. For water deficit experiments, was used a completely randomized design and treatments with three replications, arranged in a 3x2x4x2 factorial scheme: three soil water conditions (50%, 100% of soil water retention capacity (CRA) and water column (5.0 cm)), two cultivar (IRGA 424 RI and Guri INTA CL), four doses of Si (0, 4.0, 8.0 and 16 g L-1) and two sources of Si (sodium metasilicate and potassium metasilicate). The experimental units were pots with 500 grams of dystrophic red-yellow argisol soil, with six plants. For the cold stress experiment, the same design and treatments with three replications, arranged in a 3x2x2x4x2 factorial scheme: three temperatures (5, 10 and 20 °C), two cultivar (IRGA 424 RI and Guri INTA CL), were used two seed treatments (without and with dietholate), four doses of Si (0, 4.0, 8.0 and 16 mg L-1) and two sources of Si (sodium metasilicate and potassium metasilicate). The experimental units were petri dishes with twenty seeds. Chlorophyll index a and b, leaf area and dry matter content of shoot and root increased with increasing doses of Si in the three soil water conditions. There was an increase in the activity of the superoxide dismutase and guaiacol peroxidase enzymes in the studied cultivars as Si doses increased, decreasing the oxidative damage at the cellular level caused by water restriction. The germination process of rice seeds, the germination index and speed (IVG) and the shoot and root length were negatively influenced by the dietholate seed treatment, mainly at 5 and 10 °C, the cultivar IRGA 424 RI is more resistant to low temperature stress and the phytotoxic effects of dietholate protector. The Si metasilicate source was more efficient for increasing the germination percentage, IVG and shoot and root length of treated and non-dietholate treated seeds. Therefore, Si attenuates water stress and cold stress in dietholate-treated rice seeds.