Biostimulation effects of acoustic frequencies related to hydric stress in chili pepper (C. annuum L.).

Capsicum annuum L. is an important crop species susceptible to drought stress, characterized by capsaicinoids, phenolics, and flavonoids contents in their fruits. The use of chemically based products for growth promotion and crop protection, results in consumer and environmental health risk factors that have increased interest for the development of new strategies promoting crop growth and protection against stress factors, in an environmentally friendly way. Based on the latter, the aim of this study was to evaluate possible biostimulant effects of Capsicum acoustic frequencies related to hydric stress (CAFHS) in chili pepper (C. annuumL.) plants, at different decibel levels under greenhouse conditions. Treatments at 80, 72.5, and 69 dB were applied for 20 minutes every week for six weeks. The results showed that plants treated with 69 dB emissions were characterized by a significant higher height, stem width, phenyl alanine ammonia lyase (PAL) activity, higher phenolics, flavonoids and capsaicinoids contents, as well as significant increase in pathogenesis related gene (pr1a) expression. The results demonstrated that the application of CAFHS at 69 dB enhanced the growth and development of C. annuum plants as well as the production of secondary metabolites such as capsaicin, suggesting that its application induced biostimulation of chilli pepper. The easiness of the application of an acoustic treatment and its friendly character towards human and environmental health effects may prove that plant acoustic frequencies technology (PAFT) might be an attractive alternative for sustainable plant production in the current environmental scenario.