Abstract: We investigated the responses of aboveground biomass and root morphological characteristics of Phyllostachys edulis seedlings to nitrogen addition under different levels of drought stress. The experiment followed a two factor completely random block design, with three levels of soil water condition (CK, MD, and HD with 80%-85%, 50%-55%, and 30%-35% of field water holding capacity, respectively) and two levels of nitrogen addition (N0, 0 mg N·kg^-1; N1, 100 mg N·kg^-1). The root morphological characteristics and biomass of seedlings were measured. The results showed that nitrogen addition increased the biomass of leaf and root inPh. edulis seedlings under the same water level. Compared with N0MD and N0HD, the aboveground biomass of N1MD and N1HD increased by 15.6% and 11.9%, while the total biomass increased by 36.7% and 25.0%, respectively (P<0.05). Nitrogen addition reduced the specific root length and stem/leaf ratio of Ph. edulis seedlings under the same water level, but significantly promoted root/shoot ratio under moderate and high drought stresses (P<0.05). Under water stress, the proportion of root biomass increased significantly, while the proportion of stem and leaf biomass showed a decreasing trend with nitrogen addition. Nitrogen addition improved root morphological characteristics (root length, root surface area, root volume) of Ph. edulis. Nitrogen addition showed stronger enhancement on dry matter accumulation of Ph. edulis seedlings under moderate drought than under high drought stress, while better alleviated the stress of high drought on root morphology. In conclusion, nitrogen application prompted Ph. edulis to adjust its biomass allocation under drought stress to optimize the access to limited resources. It also facilitates to shape root morphological characteristics through alleviating the inhibitory effect of drought on the growth of Ph. edulis seedlings.

Key words: Phyllostachys edulis, nitrogen fertilization, drought stress, biomass, root system.