Title : Hydric stress and silicon in the activity of antioxidant enzymes in cv Micro-Tom tomato
Abstract:
Water usage has become controversial because it is an increasingly scarce resource. Furthermore, summer periods may drastically affect agricultural non-irrigated cultures productivity. Hydric stress can lead to decreased productivity due to physiological, metabolic and morphological changes. Silicon is considered a beneficial element, and its supplementation has been efficiently adopted for greater resistance to biotic and abiotic stresses. Under stress conditions, there is increased production of reactive oxygen species (ROS) which cause a cascade of oxidative reactions that may interfere with metabolism. However, complex protection systems are formed to compete with oxidative stress, consisting of several antioxidant enzymes such as superoxide dismutase, peroxidase and catalase. The beneficial effect of silicon has been associated with increased antioxidant defense capacity in water deficiency. Therefore, this study aimed to evaluate the effect of silicon and hydric stress on the activity of antioxidant enzymes in cv Micro Tom tomato. Four weekly applications of silicon were carried out at the following concentrations: 0; 0.5; 1; 1.5; 2; 2.5 g L-1 via leaf. After these applications, water stress was established, with total water withdrawal and rehydration. Sampling for analysis were performed before, during and after hydric stress. Superoxide dismutase, catalase and peroxidase were evaluated enzymes; leaf lipid peroxidation was also evaluated. It was observed that without water stress the plants with the highest concentration of silicon (2.5 g L-1) had high lipid peroxidation, which also caused higher activity of antioxidant enzymes. During stress and rehydration, it was also observed that the higher concentration of silicon provided a reduction in enzymatic activity and lipid peroxidation. Thus, it can be stated that, under the conditions evaluated, silicon had a beneficial effect during hydric stress and rehydration, promoting greater membrane stability.
