Growth and chemical constituents of cardoon plant in response to foliar application of various algal extracts

Abstract

Algal extracts play an important role in metabolic processes in cardoon plant (Cynara cardunculus L.). Cardoon contains phenolic compounds, fixed oil, sesquiterpenes, lactonens, flavones, sterols, coumarins, lignans, inulin, cynarin and silymarin. Also, it has medicinal properties, i.e. reduce the cholesterol, anti-diabetic, and improve the liver functions. The leaves of cardoon plant can inhibit the activity of several human pathogenic bacteria; possibly due to their specific phenolic components which have an antioxidant activity. The aim of this investigation was to evaluate the growth, seed yield and chemical constituents of cardoon due to spray with the algal extracts. Plants were treated with different doses (0, 1, 2 and 3 g/L) of four algal extracts (Spirulina platensis, Chlorella vulgaris, Amphora coffeaeformis and Scenedesmus obliquus). Morphological characters (plant height, leaf number, herb fresh weight, herb dry weight and seed yield) were recorded. Chemical contents (fixed oil, flavonoids, carbohydrates, free radical scavenging activity and phenolic compounds) were evaluated. The highest values of morphological characters were detected under 3 g/L of Spirulina platensis extract. Morphological characters increased by 70.9, 77.1, 45.6, 158.4 and 106.1% in plant height (cm); leaf number/plant, total fresh and dry weights (g/plant) and seed weight (g/plant) respectively, compared to the control. The Scenedesmus obliquus extract at 1 and 3 g/L resulted in the greatest amounts of fixed oil and total carbohydrates, the increase yielded 166.7 and 43.7% than control. Chlorella vulgaris extract in 1 and 2 g/L produced the highest increments in total flavonoids and inhibition of free radical scavenging activity, the increments were 58.8 and 105.5% than control. The highest value of total phenolic compounds was recorded due to the application of Amphora coffeaeformis extract at 3 g/L that produced 311.1% than control. Chlorogenic, caffeic and vanillic were detected as the major fractions of phenolic compounds. Algal extracts caused highly significant changes in major and minor fractions of phenolic compounds. Doses of 2, 3 g/L of Chlorella vulgaris and 2 g/L of Amphora coffeaeformis resulted in the greatest amounts of vanillic, chlorogenic and caffeic acids, these doses yielded 61.1, 31 and 66.7% respectively than control. It can be concluded that highly significant changes were reported in growth, yield and various chemical constituents of cardoon in response to the algal extracts applications.