The
Achillea millefolium L. is a perennial herb with important antibacterial, antifungal, anti-inflammatory, antitumoral, and
antioxidant properties. This
research aimed to investigate the effect of shading (75%; black net) and
nitrogen fertilization (0, 75 and 150 kg
urea ha-1) on the
nitrogen metabolism,
essential oil yield and antimicrobial activity of A.
millefolium at vegetative- and reproductive-stage. The evaluated
parameters varied depending on the organ and the phenological stage of the
plant considered. Overall, our findings indicated that shading decreased
nitrogen assimilation. Decreased activities of
nitrate reductase and
glutamine synthetase were observed on shaded
plants during reproductive and vegetative stages, respectively.
Nitrate and total
amino acid levels increased in shaded
plants at the vegetative stage. Regarding
nitrogen supply, the improved
nitrogen metabolism and
essential oil yield values were accompanied by intermediate concentrations of
urea (75 kg ha-1).
Plants fertilized with 75 kg
urea ha-1 produced the highest
amino acids concentration (vegetative stage),
ammonium concentration (vegetative stage) and
essential oil yield (reproductive stage). Shading or
nitrogen supply did not influence the microbial activity of A.
millefolium essential oil.However, the
essential oil of leaves and
flowers were highly effective against
fungi and
bacteria, especially
gram-positive bacteria. In conclusion, the current study showed that full
light and 75 kg
urea ha-1 enhanced the
nitrogen metabolism of A.
millefolium in both vegetative and reproductive stages.(AU)