J Plant Ecol ›› 2021, Vol. 14 ›› Issue (3): 555-568 .DOI: 10.1093/jpe/rtab010

• Research Articles • Previous Articles    

Effects of elevated ozone and nitrogen addition on leaf nitrogen metabolism in poplar

Bo Shang1, Zhaozhong Feng1,*, Jinlong Peng2, Yansen Xu2 and Elena Paoletti2,3   

  1. 1 Key Laboratory of Agrometeorology of Jiangsu Province, School of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044, China, 2 State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China, 3 Institute of Research on Terrestrial Ecosystems, National Research Council, via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy

    *Corresponding author. E-mail: zhaozhong.feng@nuist.edu.cn
  • Received:2020-09-08 Revised:2020-12-15 Accepted:2021-01-18 Online:2021-01-31 Published:2021-06-01

Abstract:

Aims

Ozone (O3) pollution and nitrogen (N) deposition/fertilization often simultaneously affect plant growth. However, research of their interactive effects on leaf N metabolism is still scarce. We investigated their interactive effects, aiming to better understand plant N metabolism processes and biogeochemical cycles under high O3 pollution and N deposition/fertilization.

Methods

Poplar saplings were exposed to two O3 levels (NF, non-filtered ambient air; NF60, NF + 60 ppb O3) and four N treatments (N0, no N added; N50, N0 + 50 kg N ha−1 yr−1; N100, N0 + 100 kg N ha−1 yr−1; N200, N0 + 200 kg N ha−1 yr−1) in open-top chambers for 95 days. The indicators related to leaf N metabolism were analyzed, including the activities of N-metabolizing enzymes and the contents of total N, NO3-N, NH4+-N, total amino acid (TAA) and total soluble protein (TSP) in the leaves.

Important Findings

NF60 stimulated the activities of nitrate reductase (NR) by 47.2% at August relative to NF, and stimulated glutamine synthetase (GS) by 57.3% when averaged across all N treatments and sampling times. In contrast, O3 did not significantly affect TSP and even reduced TAA content in August. Relative to N0, N200 significantly increased light-saturated rate of CO2 assimilation (Asat) by 24%, and increased total N content by 70.3% and 43.3% in August and September, respectively, while it reduced photosynthetic N-use efficiency by 26.1% in August. These results suggest that the increase in Asat and total N content are uncoupled, and that the surplus N is not used to optimize the capacity for carbon assimilation under high N treatment. Simultaneously, high N treatment significantly promoted leaf N metabolism by increasing NO3-N contents, NH4+-N contents, TAA contents and the activities of NR and GS. There was no significant interaction between O3 and N for all variables.

Key words: enzyme activity, nitrogen addition, nitrogen metabolism, ozone, poplar

摘要:
臭氧和氮添加对杨树叶片氮代谢的影响
臭氧(O3)污染和氮(N)沉降/施肥都能同时影响植物的生长。然而,几乎没有研究探究O3和N添加对植物叶片N代谢过程的复合影响。本研究在开顶式气室(OTC)中对杨树进行了为期95 d的熏蒸实验,包括两个O3水平(NF,环境O3水平;NF60,NF + 60 ppb O3)和4个N处理(N0,没有N添加;N50,N0 + 50 kg N ha−1 yr−1;N100,N0 + 100 kg N ha−1 yr−1;N200,N0 + 200 kg N ha−1 yr−1)。测定了与叶片N代谢相关的一些指标,包括叶片N代谢酶的活性、总叶片N浓度、NO3-N浓度、NH4+-N浓度、总氨基酸浓度(TAA)、总可溶性糖的浓度(TSP)。研究结果表明,相对于NF,在8月份NF60处理显著刺激了硝酸还原酶(NR)的活性,使其升高了47.2%。当平均所有的N处理和两次取样时间时,NF60处理下谷氨酰胺酶(GS)的活性比NF处理下的高57.3%。但是O3处理并没有显著影响TSP浓度,并且在8月也没有降低TAA的浓度。相对N0,高的N添加处理(N200)显著增加了杨树叶片的饱和光合速率(Asat) 24%,并且分 别在8和9月增加了总叶片N浓度70.3%和43.3%。但是在8月份,N200处理下光合N利用效率比N0的低26.1%。这表明N添加导致的Asat和叶片总的N浓度的升高是不匹配的,高N处理下,叶片中一些剩余的N没有被用于优化植物碳的同化。同时,也发现高N添加显著刺激了叶片N代谢过程,叶片中的NO3-N浓度、NH4+-N浓度、TAA浓度、NR和GS活性都显著升高。然而,O3和N添加对杨树叶片所有N代谢相关的指标都没有交互影响。这些结果将有助于更好地了解在高O3污染和N沉降/施肥下植物的N代谢过程以及生物地球化学循环过程。

关键词: 酶活性, 氮添加, 氮代谢, 臭氧, 杨树