Objective Barthea barthei (Hance ex Benth.) Krass. is a unique shrub of the genus Barthea in Melastomataceae in China, which has important ornamental value. However, it is mainly distributed in the wild, and its artificial cultivation technology system has not been fully established, which greatly limits its application potential as a landscape plant. In this study, by comparing the effects of different types in nutrients and different application concentrations on the growth and root indexes of the seedlings, the main nutrient dosage affecting the growth of the seedlings was determined, providing a scientific basis for the cultivation of the seedlings.

Method The tissue culture seedlings of B. barthei were used as materials, and they were transplanted into the seedling cups with yellow soil as the cultivation substrate. After 3 months' culture, 6 kinds of N nutrients (Glutamic acid, Alanine, Aspartic acid, Compound fertilizer, Urea, Controlled-released fertilizer) and 3 kinds of application amount (0.7, 1.4 and 2.8 mg/plant) were applied respectively. The seedling height and chlorophyll content of B. barthei were measured monthly, and the root indexes of B. barthei was measured after the experiment.

Result Nutrient type and application amount had significant effects on the early growth and development of B. barthei seedlings. The highest increment of seedling height was 5.18±0.13 cm after 1 month of treatment with T9 (Aspartic acid, 2.8 mg/plant). The increment became smaller after 4~5 months. The seedling height increment of seedlings treated with T5 (Alanine, 1.4 mg/plant) was not significantly different from that of the control in the first 2 months, but it was much higher than that of the control after the 4th and 5th months. The increment of seedling height of T18 (Controlled-released fertilizer, 2.8 mg/plant) was the largest after 4 and 5 months. The root biomass of T14 (Urea, 1.4 mg/plant), T9 (Aspartic acid, 2.8 mg/plant) and T15 (Urea, 2.8 mg/plant) were the largest, which were 0.71 (±0.40) g, 0.65 (±0.21) g and 0.64 (±0.24) g, respectively. The root surface area with diameter less than or equal to 2 mm under T9 treatment was 273.63 cm², which was significantly higher than that under other treatments.

Conclusion Considering the seedling height and root index of root surface area with diameter ≤ 2 mm, the best nutrient for the early stage of B. barthei growth was Aspartic acid with the amount of 2.8 mg/plant.