Abstract

Houttuynia cordata Thunb. is a medicinal herb rich in monoterpenes. The roles of salicylic acid (SA) in monoterpene accumulation and physiological responses of H. cordata are still limited in knowledge, hampering its application in the field. After foliar application of 0.01 mM SA, monoterpene contents, antioxidative enzyme activities, hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) contents were measured. The maximum of total monoterpene concentrations was observed 8 days after treatment. A continuous increase of superoxide dismutase and peroxidases activities after 4 and 2 days, respectively, suggested the induction of plant tolerance. H₂O₂ content did not showed an increase in SA-treated plants at the early stage, while a significant decline in MDA content was observed as compared to the controls. Moreover, although H₂O₂ was markedly induced at the later stage, MDA content was not increased. These implied that SA application led to lower lipid peroxidation. The study suggested that the application of SA might have little adverse effects on growth and development, and harvest for 8 days after SA application is critical to quality assurance of monoterpenes in H. cordata.

Key words: Antioxidative system, Houttuynia cordata, monoterpenes, salicylic acid.