Salicylic acid enhances tolerance of Valeriana officinalis L. to bentazon herbicide

Abstract

Salicylic acid is an important phytohormone, with regulation role in responses of plants to biotic and abiotic stress, especially detoxification of herbicides. For this purpose, the effect of three rates of salicylic acid (SA) (zero, 0.5, and 1 mM) and six doses of bentazon (zero, 50%, 75%, 100%, 125%, and 150% of recommended dose) on physiological response of valerian (Valeriana officinalis L.) were evaluated in the completely randomized factorial design with three replicates. The results showed that application of bentazon, especially at high levels (125% and 150% of recommended dose, in the absence of SA, exacerbated the rate of phytotoxicity damage, malondialdehyde (MDA) content, catalase (CAT), gaiacol peroxidase (GPX), and ascorbate peroxidase (APX) activity. Exogenous application of SA positively impacted bentazon- and unbentazon-exposed (control) plants, even under elevated concentration of herbicide (50% higher than recommended dose). Highest protection of the bentazon-exposed plants was observed at 0.5 and 1 mM level of SA, respectively. Combination of exogenous application (pre-treatment) of SA and bentazon herbicide reduced MDA content compared with ones were exclusively bentazon-exposed. In addition, exogenous application of SA enhanced antioxidant enzyme system, and increased APX and GPX enzyme activity. Results of present research indicated that external application of SA could be able to increase tolerance to oxidative stress generated in bentazon-exposued plants of valerian by reducing phytotoxicity and mutating antioxidant enzymatic system and antioxidant metabolites content.