Application of Spirulina platensis and Chlorella vulgaris for Improved Growth and Bioactive Compound Accumulation in Achillea fragrantissima In Vitro

Achillea fragrantissima is a medicinal herb valued for its essential oils and bioactive compounds. Microalgae, such as Spirulina platensis and Chlorella vulgaris, show considerable promise as natural biostimulants due to their high levels of protein, minerals, vitamins, and fatty acids. The individual or compound effects of S. platensis and C. vulgaris on the growth, photosynthetic pigments, and essential oil composition of A. fragrantissima in vitro were measured in this study. According to chemical analysis, S. platensis contains large amounts of protein and several minerals, including phosphorus, manganese, and iron. Conversely, C. vulgaris showed a higher percentage of carbohydrates, lipids, phytol, aldehydes, and fatty acid esters. The combination of 1.0 g·L−1 S. platensis and 0.5 g·L−1 C. vulgaris tended to stimulate callus formation. Meanwhile, the 0.5 g·L−1 C. vulgaris treatment enhanced shoot and leaf development and increased total photosynthetic pigment content. Analysis of essential oils from A. fragrantissima produced under different treatments demonstrated that combined treatments with S. platensis and C. vulgaris had greatly improved the valuable bioactive substances, such as phytol, oleic acid, 2H-pyran, and thymine. These results show the effectiveness of using S. platensis and C. vulgaris extracts as eco-friendly biostimulants.