Aclimatação de plantas de girassol à salinidade induzida por silício

Abstract

The aim of the study was to evaluate the effects of silicon (Si) in sunflower plants subjected to salinity, studying physiological and biochemical mechanisms of the plant. Sunflower seeds (cv. Catissol 01) were sown in polystyrene trays containing a mixture of sands (washed with water and sterilized by autoclaving) and vermiculite, conducted in the greenhouse. In 7th days after sowing (DAS), the seedlings were transferred to pots containing the nutrient solution of Hoagland. The beginning of the treatments occurred at 28th DAS, and evaluations of plants were carried out 14th days later. It used a factorial scheme 4 × 4, in a randomized design, with four replications, in which the factors consisted of four Si concentrations (0.0; 1.0; 1.5; and 2.0 mM) and four NaCl concentrations (0; 50; 100; and 150 mM). The salinity influenced the decrease in height and the dry matter of sunflower plants, but the presence of Si reversed this effect, resulting in taller plants and increased dry matter, compared to those not treated with this nutrient, even when subjected to saline stress conditions. As well as treatment with Siinduced lower electrolyte leakage in leaf and root tissues and higher relative water content in the leaves of plants subjected to saline stress conditions, possibly, caused by the accumulation of silica crystals in these plant tissues. The increase in Si concentrations induced the accumulation of soluble proteins, proline, and N-amino solutes in leaf and root tissues, and this result is related to the higher nitrate content and higher activity of nitrate reductase in the leaves and roots of plants treated with silicon. Oxidative damage in leaves and roots of sunflower plants were partially reduced by treatment with Si. In general, the activity of the enzyme superoxide dismutase, ascorbate peroxidase and catalase was increased in plants subjected to saline stress conditions and treated with Si. Thus, the application of Si in vegetative growth decreased the effects of salinity on sunflower plants, especially, using higher concentrations of silicon (2 mM), allowing the plants to properly acclimate conditions of saline stress, through improvements in the relative water content of the plant, the accumulation of organic solutes and an antioxidant enzyme system more efficient.