Foliar Application of Iron Oxide Nanoparticles Promotes Growth, Mineral Contents, and Medicinal Qualities of Solidago virgaurea L

Goldenrod (Solidago virgaurea L.) is considered for their medicinal properties for humans. These properties are attributed to some volatile compounds that can be extracted from above- and underground organs of plants. More ingredients of medicinal plants are undoubtedly considered by herbal medicine activists. The study aimed to promote Solidago yield and quality under foliar application of Fe(2)O(3) nanoparticles that can be considered as a safe and healthy fertilizer on the basis of US Food and Drug Administration (FDA) regulatory process about color additives. The experiment was performed with concentrations of Fe(2)O(3) nanoparticles (0, 0.5, or 1 mg L(−1)) and foliar application times (1, 2, 3, 4, or 5 times) on 4- to 5-leaf plants of Solidago virgaurea. Results showed that 4 times foliar application of 1 mg L(−1) caused the best plant growth and mineral element contents (nitrogen, phosphorous, potassium, copper, and zinc) except for Fe content that the more the times of foliar application, the more the Fe content increased. However, the flavonoid (rutin and quercetin) and essential oils (caryophyllene, alpha-pinene, camphene, limonene, linalool, myrcene, and terpinene) as biochemical and medicinal qualities of the treated plants were remarkably promoted when 1 mg L(−1) of nanoparticles was sprayed 5 times. Furthermore, the more the element contents, the more the ingredients. Finally, based on the goals of herbal medicine activists for the production of the essence, extract, or herb, both 5 and 4 times of foliar applications of ferric oxide nanoparticles are safe and may be economic and recommendable.