Effects of nitrogen supply with different NO₃^–/NH₄⁺ ratios on growth and medicinal components of Pogostemon cablin

ObjectivesThe aim of this paper was to study the suitable supply ratio of NO₃^–/NH₄⁺ for high yield and contents of medicinal functional composition in Pogostemon cablin.

MethodsThe 6 cm tissue culture seedlings of Hainan Pogostemon cablin were taken as the research material in a sand culture experiment. Five ratios of NO₃^–-N/NH₄⁺-N were set up: 100∶0, 75∶25, 50∶50, 25∶75 and 0∶100. Each pot was planted with 1 seedling and irrigated with 250 mL of N solution each time and at 10 day intervals. The plant samples were collected 60, 120, 180 and 240 days after the transplanting. The patchouli growth indexes, chlorophyll composition and antioxidant activity and efficacy were analyzed.

ResultsThe NO₃^–-N/NH₄⁺-N ratio of 75∶25 promoted plant height, basal culm thickness, tiller number, leaf area index, above-ground fresh and dry biomass, shoot oil rate, leaf oil rate, whole plant oil rate and plant oil amount, and also improved the contents of chlorophyll a and chlorophyll (a + b). The NO₃^–-N/NH₄⁺-N ratio of 75∶25 was better for the absorption of N, P, K, Ca and Mg; the ratio of 50∶50 was beneficial to improve the content of chlorophyll b; the ratios of 25∶75 and 50∶50 were more conducive to improve the free radical scavenging rate of hydroxyl, superoxide anion and DPPH; the ratio of 50∶50 was more conducive to increase activities of PAL enzyme; the ratio of 50∶50 increased the pogostone contents of the shoots and leaves of Patchouli. The NO₃^–-N/NH₄⁺-N ratio of 25∶75 was favorable for increasing the contents of patchouli alcohol and other main medicinal components. The nitrate nitrogen and ammonium nitrogen (NO₃^–-N/NH₄⁺-N in 100∶0 and 0∶100) had negative effect or inhibition in the formation and accumulation of main medicinal composition of oil in shoots and leaves of patchouli.

ConclusionsNitrogen supply in NO₃^–/NH₄⁺ ratio of 75∶25 can stimulate the growth and high photosynthetic efficiency of Patchouli cablin, while those in the 50∶50 and 25∶75 can enhance the antioxidant and PAL enzyme activities, which is favorable to improve the components of Patchouli cablin.