Yield, essential oil and pigment content of Calendula officinalis L. flower heads cultivated under salt stress conditions

Flower heads of Calendula officinalis L. are used for medicinal or culinary purposes. Since Egyptian agricultural lands contain salt, this study investigated the effects of saline irrigation water on yield (fresh and dry weights of flower heads), essential oil (EO) yield, chemical constituents of the EO and total flavonoids and carotenoids of flower heads at three flowering stages, i.e. initial (21 days after bud formation (DABF)), full flowering (81 DABF) and final (111 DABF). After plants were treated with different levels of saline irrigation water (0.39, 1.56, 3.13, 4.69, 6.25, 7.81 and 9.38 dS m−1) consisting of NaCl, CaCl2 and MgCl2 salts, the flower head yield and pigment (total flavonoids and carotenoids) content were significantly reduced. Irrigation with saline water increased the EO content and its main components (α-cadinol, γ- and Δ-cadinene). Fresh and dry weights of flower heads and EO increased near 81 DABF while the content of pigments increased by 111 DABF.

Research highlights▶ Saline irrigation water decreased the fresh and dry weights of flower heads, and pigment contents (total flavonoids and total carotenoids) but increased essential oil yield and its main components (α-cadinol, γ- and Δ-cadinene) of Calendula officinalis. Fresh and dry weights of flower heads and essential oil increased towards the full bloom stage of flowering while pigment content, such as total flavonoids and total carotenoids, increased.