Effects of nitrogen deposition on VOCs emission and its relationship with photosynthesis, growth, accumulation and distribution of NSC in Moso bamboo tree (Phyllostachys edulis)

Atmospheric nitrogen (N) deposition is a significant driver of global change and disrupts the carbon and nitrogen cycles in ecosystems. Volatile Organic Compounds (VOCs) emitted by plants play an important role in regional air quality and the carbon cycle. This study investigates the effects of different forms and doses of N deposition on Biogenic Volatile Organic Compounds (BVOCs) emissions, photosynthesis, growth, and non-structural carbohydrate (NSC) accumulation in the widespread subtropical bamboo species-Moso bamboo (Phyllostachys edulis). A pot experiment was conducted with three N doses: 100 kg(N)·hm⁻²·a⁻¹ (L1), 200 kg(N)·hm⁻²·a⁻¹ (L2), and 0 kg(N)·hm⁻²·a⁻¹ (L0), using ammonium N (AN), nitrate N (NN), and a mixed N form (AN+NN). Dynamic headspace sampling was used to assess the effects of N deposition on BVOC emissions and the relationships between N deposition, photosynthesis, plant growth, and NSC distribution throughout the growing season.

The results indicated that N deposition increased BVOC emissions, with the highest emissions occurring under NN treatment at L1 during March and June. Isoprene (ISO) emissions were significantly enhanced under AN treatment, with L2 doses increasing ISO emissions by 99.20% compared to L1. The AN+NN treatment resulted in higher ISO emissions at L2, with increases of 76.02% and 141.69% compared to AN and NN alone, respectively. N form and dose also influenced photosynthetic pigments, with the highest total chlorophyll content observed under AN+NN at L1. Photosynthetic parameters, including net photosynthetic rate (Pn), stomatal conductance (Gs), and carboxylation efficiency (CE), were significantly higher under L1 compared to L0. A positive correlation was found between chlorophyll content and VOC emissions, with Pn, Gs, and CE strongly correlating with ISO emissions. Growth responses varied by N form. AN+NN treatment significantly promoted the growth of Phyllostachys edulis, particularly in above-ground biomass, while AN inhibited root and whip growth. Biomass of leaves and culms was significantly higher under L1 treatment, with increases of 85.60% and 38.14%, respectively, compared to L0 under AN treatment. Soluble sugar content in leaves, culms, and roots was highest at L1, with decreases observed as the N dose increased. Soluble sugars in leaves, culms, and buds increased by 24.85%, 24.92%, and 21.20% under L1 compared to L0. Starch content in leaves and culms increased initially but declined under higher N doses. AN and NN treatments at L2 reduced starch content in leaves and culms, with significant reductions observed in both N forms.

NSC content was positively correlated with ISO emissions, especially for soluble sugars. Total NSC content and soluble sugars were also positively correlated with BVOC emissions, suggesting that NSCs play a key role in plant responses to environmental stress. In conclusion, N deposition—particularly in mixed forms (AN+NN)—enhances BVOC emissions, especially ISO emissions, promotes biomass accumulation, and improves photosynthetic capacity. Lower N doses support higher ISO emissions and NSC accumulation. This study highlights that appropriate levels of N deposition can support bamboo growth and improve resilience to atmospheric changes.