Ácido salicílico como atenuante dos danos causados pelo estresse salino em capuchinha (Tropaeolum majus L.)

Abstract

Saline stress is one of the main abiotic stresses responsible for low crop productivity due to the disturbances it causes to plants. Nasturtium (Tropaeolum majus) is a plant used in ornamentation, food and medicine. However, saline stress limits the development and productivity of this plant due to biochemical and physiological disturbances. In this context, the application of salicylic acid is an alternative to mitigate the harmful effects of salt stress on plants such as nasturtium. With this, the objective was to evaluate the effect of applying salicylic acid as a mitigation of the harmful effects of salt stress on the growth, gas exchange, bioactive compounds and antioxidant enzymes of nasturtium. To this end, an experiment in a completely randomized design, in a 3 x 3 factorial scheme, referring to 0 (no stress) 50 (moderate salt stress) and 100 (severe salt stress) mM NaCl and application of 0, 0.5 and 1 mM salicylic acid, with six replicates, was used. In article I, with data up to the middle of the crop cycle, it was observed that the application of salicylic acid had a positive effect in mitigating the effects of severe saline stress, resulting in a significant increase in the number of leaves, with the highest dose being The concentration of 1 mM is effective, also leading to notable improvements in water use efficiency and photochemical efficiency. However, other combinations of salinity and salicylic acid reduced growth and gas exchange in nasturtium plants. In article II, which concerns the end of the crop cycle, it was observed that salicylic acid had a positive effect in mitigating the effects of saline stress, increasing the number of leaves and initial and maximum fluorescence. Under moderate salt stress, salicylic acid promoted an increase in anthocyanin levels, however its use decreased reducing sugars, total sugars and ascorbic acid. There was an increase in superoxide dismutase activity in nasturtium plants under moderate and severe salt stress using salicylic acid, as well as an increase in catalase activity under severe salt stress. Application of salicylic acid also reduced catalase and ascorbate peroxidase activity in non stressed plants. In summary, the application of 1 mM salicylic acid is a viable strategy to mitigate the harmful effects of salt stress on nasturtium, however, its application did not increase number of flowers.