Germinação, vigor e atividade antioxidante em Passiflora incarnata L. sob efeito do timol

Abstract

The seeds of the Passifloraceae family have a low germination rate, due to the existence of dormancy, with the increase in the production of reactive oxygen species (ROS) is a common feature in the seed germination process and requires the activation of a complex antioxidant system. Thymol is an antioxidant compound easily found in species of the Lamiaceae and Verbenaceae families, with the potential to reduce cell damage caused by ROS, benefiting germination and plant vigor. This study aimed to evaluate the germination and vigor of seeds and seedlings of wild passion fruit (Passiflora incarnata L.), through the exogenous application of thymol. The first experiment evaluated the effects of thymol (absence or presence, via seed immersion treatment – 1 mg L-1) and temperature (constant 35ºC and alternating 20-30ºC) on seed germination in the laboratory. The evaluations were carried out at 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26 and 28 days of germination, respectively, to determine the germination parameters (percentage and speed). Then, in the second experiment, the effect of thymol on seed germination in trays was evaluated via seed immersion treatment and/or foliar spraying, evaluating seedling growth by length and dry mass of shoot and root, activity of antioxidant enzymes (catalase; ascorbate peroxidation and superoxide dismutase), content of total phenolic compounds, content of total flavonoids and evaluation of the antioxidant activity of the leaf ethanol extract. The thymol compound did not show a positive effect on the germination of P. incarnata L. in experiment 1, with the best temperature condition being 35ºC constant. In experiment 2, the treatment with thymol via seed immersion resulted in an increase in the concentration of phenolic compounds in the plants and the application via foliar caused an increase in shoot dry mass, showing the biostimulating effect of this compound.