Physiological and Biochemical Adaptation of Common Garden Plants to Inorganic Nitrogen-Laden Fine Particulate Matter Stress
Keqin Xiao | Yiying Wang | Rongkang Wang | Zhanpeng Hu | Sili Peng | Zimei Miao | Zhiwei Ge
Accelerated urbanization has intensified nitrogen deposition and fine particulate matter (PM<sub>2.5</sub>) pollution. While urban landscape plants play a vital role in atmospheric remediation, systematic exploration of their adaptation strategies to these dual stressors remains limited. This study investigated the dynamic responses of antioxidant defense systems and nitrogen/weight ratios of <i>Iris germanica</i> L. and <i>Portulaca grandiflora</i> Hook. under four nitrogen deposition scenarios (N0, N1, N2, and N4 with nitrogen concentrations of 0, 15, 30, and 60 kg N·hm<sup>−2</sup>·a<sup>−1</sup>, respectively) combined with constant PM<sub>2.5</sub> exposure (50 μg/m<sup>3</sup>). Through fumigation experiments, we demonstrated that <i>Iris germanica</i> L. showed higher sensitivity to inorganic nitrogen-laden PM<sub>2.5</sub> stress than <i>Portulaca grandiflora</i> Hook. Both species exhibited stronger antioxidant enzyme (SOD, CAT, POD) activities in the high-growth season compared to the low-growth season. Nitrogen allocation analysis revealed that <i>Portulaca grandiflora</i> Hook. maintained stable nitrogen content across treatments, while <i>Iris germanica</i> L. showed progressive nitrogen loss under high nitrogen-laden PM<sub>2.5</sub> exposure. These findings establish <i>Portulaca grandiflora</i> Hook.’s superior resilience through two synergistic mechanisms: modulated antioxidant systems and efficient nitrogen remobilization. This comparative study provides actionable insights for selecting pollution-tolerant species in urban green infrastructure planning.
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