Effects of simulated nitrogen deposition on Phyllostachys edulis (Carr.) seedlings under different watering conditions: is seedling drought tolerance related to nitrogen metabolism?

Drought stress is an important limiting factor of plant performance, and how it interacts with increasing nitrogen (N) deposition to affect seedling development requires further investigation. This study addresses the combined effects of N deposition and drought on growth and physiological attributes of Phyllostachys edulis (Carr.) seedlings. Seedling growth attributes and nitrogen metabolism indicators were evaluated after the fast-growing period in the presence of four simulated N deposition rates (control, 0 kg·ha−1·yr−1; low N, 30; medium N, 60; high N, 90) and two watering conditions (normal, 75 ± 5% of field capacity; or drought, 35 ± 5%). Drought stress significantly inhibited P. edulis seedling growth and N metabolism. Under normal watering conditions, greater simulated N deposition was associated with higher seedling component mass, free amino acid and soluble protein content in leaves, and enzyme activity related to N metabolism. Under drought conditions, medium N deposition maximized seedling component mass and enzyme activity related to N metabolism. Overall, low and medium N deposition improved seedling performance under drought conditions, but high N deposition did not. Moderate N deposition can partially offset the negative effects of drought stress on P. edulis seedling development.