Document Type : Research Paper

Authors

• Afsoon Rezaie Allolo ¹
• Azizollah Kheiry ²
• Mohsen Sanikhani ³
• Maliheh Yaghoobi ⁴

¹ Department of Horticulture, Faculty of Agriculture, University of Zanjan, Iran

² Department of Horticultural science, Faculty of Agriculture, Universit of Zanjan, Iran

³ Faculty of Agriculture- Horticulture University of Zanjan, Iran

⁴ Department of Chemical Engineering, Faculty of Engineering, University of Zanjan, Zanjan, Iran

Abstract

Background and objectives: Digitalis purpurea L., the most well-known species of the Digitalis genus, is a biennial plant containing cardiac glycosides (0.3 to 0.4%) in its leaves. These glycosides are extracted and used as natural medicines for treating heart diseases, with no chemical substitutes available, making them widely utilized annually. In recent years, using amino acids and growth regulators as alternatives to chemical compounds has gained popularity for enhancing secondary metabolites, improving the quality and quantity of agricultural products, and promoting sustainable agriculture. This study investigates the biochemical and growth responses of D. purpurea to foliar applications of glutamic acid and benzyladenine under greenhouse conditions to evaluate their effects on morphophysiological characteristics, yield improvement, and their potential as environmentally friendly alternatives to chemical fertilizers.
Methodology: A completely randomized design with three replications was conducted in the research greenhouse of the University of Zanjan to evaluate the effects of foliar applications of benzyladenine (0.5 and 1 mM) and glutamic acid (1 and 2 mM), along with a control treatment (distilled water). Seeds were initially planted in a seedling tray containing cocopeat and peat moss. At the four-leaf stage, three seedlings were transplanted into plastic pots filled with a culture medium of field soil, cocopeat, and perlite (1:1:3 ratio). Greenhouse conditions were maintained at average day and night temperatures of 25°C and 18°C, respectively, with 80% relative humidity. Seedlings were irrigated weekly with 100 mL of complete Hoagland solution. Foliar spraying with the treatments began after seedling establishment in late June and was repeated four times at 10-day intervals. Leaf samples were collected 10 days after the final application for laboratory analysis. Data were analyzed using SAS software (version 9), and means were compared using Duncan’s multiple range test at a 5% probability level.
Results: The application of 1 mM benzyladenine resulted in the highest total chlorophyll content (1.95 mg/g fresh weight), antioxidant activity (36.02%), and peroxidase enzyme activity (1.14 U/mg protein per minute). The maximum total carotenoid content (0.14 mg/g fresh weight), total phenol (12.52 mg gallic acid/g fresh weight), total flavonoid (2.86 mg quercetin/g fresh weight), and nitrogen content (1.46%) were achieved with one mM glutamic acid. Additionally, one mM glutamic acid application led to the highest catalase enzyme activity (4.09 U/mg protein per minute), fresh weight (123.51 g), and dry weight (47.38 g).
Conclusion: The findings suggest that applying glutamic acid and benzyladenine at varying levels can significantly enhance the biochemical and growth characteristics of Digitalis purpurea L.

Keywords

• Antioxidant capacity
• carotenoid
• catalase
• flavonoid
• peroxidase

Main Subjects

• Agriculture and horticulture