ObjectiveThe effects of nitrogen application on the growth and triterpenoids accumulation of Cyclocarya paliurus were studied in order to provide theoretical basis for regulating the cultivation of medicinal plantation and improving the triterpenoids yield per unit area of medicinal plants.

MethodThe 1-year-old seedlings of C. paliurus were used as test materials under five different N levels, including N1 (0 g/plant), N2 (1 g/plant), N3 (3.4 g/plant), N4 (6 g/plant), N5 (10 g/plant). And the seedling height, ground diameter, biomass, total triterpenoid and three main triterpenoids were measured in the middle and late days of each month from May to August.

Result(1) The seedling height and ground diameter growth of C. paliurus increased first and then decreased with increased N application, and the highest net growth of seedling height and basal diameter were got in treatment N4, increased by 103.90% and 57.58%, respectively compared with N1. Similar variation pattern was also observed for the biomass and total biomass accumulation in roots, stalks and leaves, and the greatest total biomass accumulation was got in treatment N4, reaching 7.24 g. (2) With the increase of N application, the N content in leaves of plants increased linearly (that in roots and stalks was comparatively stable), while the C content did not change significantly, resulting in the C/N in leaves decreased linearly, and ranged from 20.42% to 12.19%. (3) Leaf was the main accumulating organ in C. paliurus, and the largest total accumulation and three individual triterpenoids (arjunolic acid, cyclocaric acid B and cyclocarioside I) in leaf showed a single peak variation pattern, with the peak values of 2.45, 0.73, 0.44 and 22.95 mg/g, respectively under relatively low N condition (N2). In addition, among the three individual triterpenoids tested, the main individual triterpenoid was arjunolic acid (0.73 mg/g, dry mass), followed by cyclocaric acid B (0.23 mg/g, dry mass) and cyclocarioside I (0.12 mg/g, dry mass). (4) N application significantly affected the yield of total and three individual triterpenoids in C. paliurus and the triterpenoid and arjunolic acid per plant reached highest under treatment N3, ranged in 95.21−279.45 mg/plant and 4.64−17.21 mg/plant. The yield of total triterpenoid and three individual triterpenoids per plant were found lowest under treatment N1 or N5.

ConclusionModerately high N application could promote the growth of C. paliurus seedlings, while moderately low N application could promote the accumulation of triterpenoid.