Nitric oxide regulates spearmint (Mentha spicata L.) responses to phenolic acids: growth, phenolics, and antioxidant capacity

Abstract

Given the widespread recognition of the health risks and environmental damages caused by synthetic herbicides and fertilizers, it is more than ever necessary to unravel the mechanisms underlying plant responses to naturally derived bioactive substances. Phenolic acids constitute a group of aromatic compounds that, by showing both growth-promoting and allelopathic effects, have gained momentum over the past years. We aimed to investigate the effects of some common benzoic acid derivatives, namely vanillic acid (VA), p-hydroxybenzoic acid (pHBA), gallic acid (GA), and salicylic acid (SA), and the alleviative effects of nitric oxide (NO) on phenolic acid-induced inhibition in growth parameters in spearmint (Mentha spicata L.) shoot and underlying mechanisms. pHBA and VA at 0.5 mM were the most influential phenolic acids in the inhibition of growth and increasing the contents of malondialdehyde (by 119% and 83% respectively) and H₂O₂ (by 83% and 108% respectively) and decreasing chlorophyll content despite accelerating the activities of catalase and superoxide dismutase. In contrast, 0.5 mM SA and 0.05 mM GA significantly increased shoot fresh weight (by 85.1% and 48.1% respectively) and the accumulation of total phenolics (by 302% and 31% respectively) and anthocyanins (by 79% and 49% respectively) and stimulated phenylalanine ammonia lyase (PAL) activity (by 140.4% and 107.7% respectively). NO at 100 µM was highly effective in the alleviation of pHBA and VA-induced growth reduction and lipid peroxidation. In conclusion, NO improved the negative effects of pHBA and VA by increasing PAL activity and enhancing the contents of antioxidative secondary metabolites.

Keywords:

• Antioxidant capacity
• benzoic acid derivatives
• Mentha spicata L.
• nitric oxide
• phenylalanine ammonia lyase
• total phenolics content

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The datasets supporting this study are not publicly available as they are part of an ongoing doctoral dissertation project, but are available from the corresponding author upon request [Nikoo Azad; Email: [email protected]].

Authors’ contribution

This research paper was accomplished with the collaboration of all people named as authors. Nikoo Azad has contributed to the major bench experiments. Dr. Hassan Ebrahimzadeh, Dr. Vahid Niknam and Dr. Mehrdad Behmanesh equally designed the experiments. All authors have read and approved the manuscript.

Additional information

Funding

This work was supported by the College of Science, University of Tehran.