Abstract: In this study, one-year-old Melastoma candidum cutting seedlings were used as experimental materials, and five gradients of N index fertilization treatments (total nitrogen 1, 3, 5, 7 and 9 g per plant, respectively) were set up. In addition, no fertilization and average fertilization (total nitrogen application was 5 g per plant) were set as control treatments. The effects of nitrogen fertilizer exponential fertilization on the growth of M. candidum seedlings were discussed by measuring mortality, seedling height, ground diameter, biomass, chlorophyll SPAD value and photosynthetic characteristics, combined with membership function analysis. The results showed that treatment 4 (17.50 g nitrogen fertilizer per plant) was the most significant, and its seedling height, ground diameter, biomass, net photosynthetic rate, stomatal conductivity, intercellular CO₂ concentration, transpiration rate and water use efficiency could reached the maximum value, but root-shoot ratio and stomatal limitation value reached the minimum value. The comprehensive value of membership function of treatment 4 was the highest. Therefore, we concluded that the exponential fertilization treatment 4 had the best fertilization effect for M. candidum, that was, the exponential fertilization treatment of 17.50 g nitrogen fertilizer per plant.

Key words: Melastoma candidum, exponential fertilization, nitrogen fertilizer, photosynthetic characteristics

摘要： 以一年生野牡丹Melastoma candidum扦插苗为试材，设置5个梯度N素指数施肥处理(施氮总量分别为1、3、5、7、9 g·株^–1)，以不施肥和平均施肥(施氮总量为5 g·株^–1)为对照，通过测定苗高、地径、生物量、叶绿素SPAD值和光合特性等指标，结合隶属函数分析进行综合评价，探讨N素指数施肥对野牡丹幼苗生长的影响。结果表明，处理T4 (17.50 g 氮肥·株^–1)表现最为显著，其苗高、地径、生物量、净光合速率、气孔导度、胞间CO₂浓度、蒸腾速率和水分利用效率均达最大值，根冠比和气孔限制值达最小值，处理T4的隶属函数综合值最高。因此，指数施肥处理T4的施肥效果最佳，即每株野牡丹施17.50 g氮肥的指数施肥处理。

关键词: 野牡丹, 指数施肥, 氮肥, 光合特性