Chitosan and riboflavin treatments affect marjoram growth, yield, and chemical composition

Marjoram is primarily cultivated to produce dried leaves and essential oil. Its active components have a wide range of biological and pharmacological activities in modern medicine. There is an interest in increasing marjoram production for local production and export. Chitosan (CH) and riboflavin (R) are required to promote plant growth and active ingredients. The purpose of this study was to investigate how marjoram performance was affected by foliar spraying of CH and R at different concentrations. This investigation was performed over two successive seasons at two cuts. The used concentrations of CH were 100, 150, and 200 ppm, while R concentrations were 50 and 100 ppm. They were applied four times as a foliar spray to the vegetative growth during the growth season. At each harvest, the following parameters were recorded: fresh and dry weight, oil yield, total carbohydrates %, protein %, macronutrient content, total phenolics content, flavonoids content, antioxidant activity, and essential oil constituents to study their response to different treatments. All the treatments of CH and R enhanced the vegetative growth, essential oil percentage, yield, active constituents, and oil components compared with untreated plants. Foliar application of CH at 200 ppm and R at 100 ppm increased plant growth, yield of volatile oil as well as chemical constituents compared with other treatments; however, CH was more effective than R. The combined application between CH and R resulted in the greatest values especially when both were applied at high doses.