Perlite particle size and NO3-/NH4+ ratio affect growth and chemical composition of purple coneflower (Echinacea purpurea L.) in hydroponics.

• Plant growth conditions is specific of each plant. • Different perlite particle sizes can affect the plant growth conditions. • Using of very fine perlite with mixture of peat moss can improve the growth properties. • Different NO 3 − /NH 4 + ratios have significant effects on phytochemical compounds. • Growing of medicinal plants in hydroponic systems needs precise investigates. Humans have relied on nature throughout their ages to cater for their basic needs including medicines to cure a wide spectrum of diseases. So, it seems necessary to increase the phytochemical compounds of medicinal plants by using effective strategies. In this research, effect of different particle sizes of perlite (very coarse perlite (more than 2 mm), medium perlite (1−1.5 mm), and very fine perlite (less than 0.5 mm)) and its mixture with peat moss (at 50:50 v/v and 30:70 v/v peat moss to perlite ratios) at two NO 3 −/NH 4 + ratios (90:10 and 70:30) were investigated for hydroponic Echinacea purpurea medicinal plant production in greenhouse conditions. According to results, different sizes of perlite and various NO 3 −/NH 4 + ratios had significant effects on plant growth parameters including the plant height, total fresh leave weight, fresh root weight, total biomass, total chlorophyll, and leaf area; meanwhile, phytochemical properties including total phenolic and flavonoid content, and various anti-radicals scavenging activities of E. purpurea were significantly varied for various growing media. The medium containing very fine-grade perlite with 50:50 v/v perlite to peat moss ratio had the optimum performance for E. purpurea plant growth parameters and phytochemical properties. It has been found that an increase of NO 3 -/NH 4 + ratio caused a significant increase in plant growth parameters and the phytochemical properties of E. purpurea. [ABSTRACT FROM AUTHOR]