title: Effects of ammonium to nitrate ratio on growth, nitrogen metabolism, photosynthetic efficiency and bioactive phytochemical production of Prunella vulgaris.
abstract: BACKGROUND
  Prunella vulgaris L (Labiatae) is commonly used as a traditional medicinal herb in some Asian and Europe countries. To date, few studies have been conducted to determine the influence of [Formula: see text] - N/[Formula: see text] - N ratio on growth, physiological development, and bioactive phytochemical accumulation in hydroponically grown P. vulgaris.
  
  
  OBJECTIVE
  The current study was conducted to evaluate the effect of five [Formula: see text] - N/[Formula: see text] - N ratios on growth, nitrogen metabolism, photosynthetic efficiency, and bioactive phytochemical production in P. vulgaris.
  
  
  METHODS
  Hydroponically cultivated P. vulgaris were fertilized with five [Formula: see text] - N/[Formula: see text] - N ratios in a greenhouse for 85 d. Dried weight of root, stem, leaf and spica, leaf area, photosynthetic efficiency, activities of nitrate reductase (NR), glutamine synthetase (GS), and the concentrations of N, soluble protein, and free amino acids in the leaves, as well as the contents of rosmarinic acid (RA), ursolic acid (UA), and oleanolic acid (OA) in the spicas were measured.
  
  
  RESULTS
  Both [Formula: see text] - N and [Formula: see text] - N as the sole source of nitrogen had inhibitory effects on P. vulgaris growth. P. vulgaris fertilized with the 25/75 ([Formula: see text] - N/NO3 - N) ratio had the highest leaf area, photosynthetic rate, and chlorophyll content. The 25/75 ([Formula: see text]/[Formula: see text]) ratio increased the spica biomass by 1828%, nitrate-reductase (NR) activity by 98%, and soluble protein concentration by 29.45% compared with the 100/0 ([Formula: see text]/[Formula: see text]) treatment. Additionally, 25 [Formula: see text] - N/75 NO3 - N resulted in the highest contents of RA and total flavonoids as well as relatively high contents of UA and OA; therefore, this ratio had the highest yield of RA, UA, OA, and total flavonoids in spicas.
  
  
  CONCLUSIONS
  The use of 25 [Formula: see text] - N/75 [Formula: see text] - N is recommended to improve biomass production and medicinal quality of P. vulgaris.
authors.affiliation: Institute of Chinese Medicinal Materials, Nanjing Agricultural University , Nanjing , PR China and.
authors.forename: Zai-Biao
authors.initials: ZB
authors.lastname: Zhu
authors.forename: Man-Man
authors.initials: MM
authors.lastname: Yu
authors.forename: Yu-Hang
authors.initials: YH
authors.lastname: Chen
authors.forename: Qiao-Sheng
authors.initials: QS
authors.lastname: Guo
authors.forename: Li-Xia
authors.initials: LX
authors.lastname: Zhang
authors.forename: Hong-Zhuan
authors.initials: HZ
authors.lastname: Shi
authors.forename: Li
authors.initials: L
authors.lastname: Liu
mesh_terms: D064751:Ammonium Compounds / Q000737:chemistry*; D018533:Biomass; D008519:Medicine, Traditional; D009566:Nitrates / Q000737:chemistry*; D009584:Nitrogen / Q000378:metabolism*; D010788:Photosynthesis / Q000502:physiology; D031347:Prunella / Q000737:chemistry / Q000254:growth & development / Q000502:physiology*
chemical_list: D064751:Ammonium Compounds; D009566:Nitrates; D009584:Nitrogen
keywords: Ammonium/nitrate ratios; bioactive-component; photosynthetic rate