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| Ammonia release from vegetation canopies and its contribution to grassland ammonia volatilization and source apportionment |
| Received:February 21, 2022 Revised:April 25, 2022 |
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| KeyWord:C3 plant;C4 plant;ammonia volatilization;photorespiration;phenylalanine metabolic pathways;glutamine synthase |
| Author Name | Affiliation | E-mail | | BAI Yinghui | College of Natural Resources and Environment, Northwest A&F University, Shaanxi 712100, China | | | XU Yinghao | College of Natural Resources and Environment, Northwest A&F University, Shaanxi 712100, China | | | Lü Shenqiang | College of Natural Resources and Environment, Northwest A&F University, Shaanxi 712100, China | | | LI Jia | College of Natural Resources and Environment, Northwest A&F University, Shaanxi 712100, China | | | LI Huitong | College of Natural Resources and Environment, Northwest A&F University, Shaanxi 712100, China | | | YANG Zeyu | College of Natural Resources and Environment, Northwest A&F University, Shaanxi 712100, China | | | WANG Linquan | College of Natural Resources and Environment, Northwest A&F University, Shaanxi 712100, China | linquanw@nwsuaf.edu.cn |
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| Abstract: |
| The main aims of this study were to quantify soil ammonia volatilization（AV）and canopy ammonia emission（AE）of three lawn varieties and to investigate the physiological mechanism of canopy emission and its contribution to turfgrass AV. A randomized block experiment was used, which included three varieties（Ophiopogon japonicus, tall fescue, and bermudagrass） and three fertilization treatments（no nitrogen treatment, 30 g·m-2 slow-release urea, and 30 g·m-2 urea） . The soil and canopy ammonia emissions were monitored in situ with a portable ammonia detector between March 2021 and November 2021, and glycolate oxidase（GO）and glycine decarboxylase （GDC） , glutamine synthase（GS） , and phenylalanine ammonia lyase（PAL）activities in the canopy were measured by enzyme -linked immunosorbent assay. The results were as follows： the accumulated soil AV, canopy AE, and total ammonia loss in the tall fescue, bermudagrass, and O. japonicus were 2.8-135.3, 1.6-101.6 kg · hm-2 · a-1, and 4.4-236.9 kg · hm-2 · a-1, respectively. The application of nitrogen fertilizer significantly increased soil AV and canopy AE. The response of bermudagrass to nitrogen fertilizer was greater than that of O. japonicus and tall fescue. Canopy ammonia emissions were important sources of turf fields, contributing approximately 37%-39% of the total turf field volatilization. Canopy ammonia fluxes were significantly positively affected by PAL and apoplast pH and significantly negatively regulated by GDC（P<0.05）in C4 plants. Soil AV was mainly controlled by soil ammonium nitrogen（P<0.05） . In conclusion, canopy ammonia emissions had pivotal impact on the turf field AV; both C3 and C4 plant canopy ammonia emission sources were phenylalanine metabolic pathways, and it was directly negatively regulated by photorespiration and nitrogen assimilation in C4 plants; however, it was indirectly negatively regulated by photorespiration via the phenylalanine metabolic pathway in C3 plants. |
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