The effect of different ammonium to nitrate ratios on antioxidant activity, morpho-physiological and phytochemical traits of Moldavian balm (Dracocephalum moldavica)

Improving yield and secondary metabolites production of medicinal plants through nutrition management recently has been considered. The present study was done to determine the effects of different ammonium (NH4+) to nitrate (NO3−) ratios (100:0, 75:25, 50:50, 25:75, 0:100) on morphophysiological, nutrient contents (N, P, K, Ca, and Mg), phenolic compounds (Total phenolics (TPC) and flavonoid (TFC) contents and individual phenolics including chlorogenic acid, rosmarinic acid, gallic acid, cinnamic acid, caffeic acid, rutin, p-Coumaric acid, apigenin, and quercetin by HPLC–DAD), essential oil composition (by GC and GC–MS), and antioxidant capacity (by DPPH and FRAP assays) of Moldavian balm (Dracocephalum moldavica L.) in deep water culture (DWC) system. The highest biomass and morphological traits values of D. moldavica observed in 0:100 ratio of NH4+:NO3−. Also, the highest TPC and TFC was earned in plants that supplied with 0:100 ratio of NH4+:NO3−. Using the 25:75 ratio of NH4+:NO3− caused the highest nutrient contents (N, Ca and Mg) in the leaves. p-Coumaric acid was detected as the major abundant phenolic compound in extracts and the application of 75:25 ratio of NH4+:NO3 resulted in the highest amounts of p-Coumaric acid, gallic acid, rosmarinic acid, caffeic acid, quercetin, and rutin. The highest antioxidant capacity by both FRAP and DPPH assays was obtained in 75:25 ratio of NH4+:NO3−. Also, the highest geranial and geranyl acetate, geraniol, and neral were obtained in 75:25, 25:75, and 50:50 ratios of NH4+:NO3−, respectively. Plants supplied with the 0:100 ratio of NH4+:NO3−, had the highest total carotenoids, while the highest chlorophyll a and b content gained with 75:25 ratio of NH4+:NO3−. These results suggest that the management of N source in nutrient recipe could contribute to enhance of morphophysiological traits, antioxidant activity and phytochemical compounds in Moldavian balm.