College of Resources and Environment, Southwest University, Chongqing, China.
College of Natural Resources and Environment, Northwest A&F University, Yangling, Shaanxi, China.
Plant Biol (Stuttg). 2024 Apr;26(3):467-475. doi: 10.1111/plb.13621. Epub 2024 Mar 11.
Ammonium nitrogen (NH -N) is essential for fruit tree growth, but the impact of excess NH -N from fertilizer on evergreen citrus trees is unclear. In a climate chamber, 8-month-old citrus plants were exposed to five different hydroponic NH -N concentrations (0, 5, 10, 15 and 20 mm) for 1 month to study effects of NH -N on growth characteristics, N uptake, metabolism, antioxidant enzymes and osmotic regulatory substances. Application of 10 mm NH -N adversely affected root plasma membrane integrity, root physiological functions, and plant biomass. MDA, CAT, POD, APX and SOD content were significantly correlated with leaf N metabolic enzyme activity (GOGAT, GDH, GS and NR). GDH was the primary enzyme involved in NH -N assimilation in leaves, while the primary pathway involved in roots was GS-GOGAT. Under comparatively high NH addition, roots were the main organs involved in NH utilization in citrus seedlings. Our results demonstrated that variations in NH concentration and enzyme activity in various organs are associated with more effective N metabolism in roots than in leaves to prevent NH toxicity in evergreen woody citrus plants. These results provide insight into the N forms used by citrus plants that are important for N fertilizer management.
铵态氮（NH 4 -N）是果树生长所必需的，但肥料中过量的 NH 4 -N 对常绿柑橘树的影响尚不清楚。在气候室内，将 8 个月大的柑橘植物暴露于 5 种不同的水培 NH 4 -N 浓度（0、5、10、15 和 20 mm）下 1 个月，以研究 NH 4 -N 对生长特性、N 吸收、代谢、抗氧化酶和渗透调节物质的影响。施用 10 mm NH 4 -N 会对根质膜完整性、根生理功能和植物生物量产生不利影响。MDA、CAT、POD、APX 和 SOD 含量与叶片 N 代谢酶活性（GOGAT、GDH、GS 和 NR）显著相关。GDH 是叶片中 NH 4 -N 同化的主要酶，而根中主要途径是 GS-GOGAT。在较高的 NH 4 添加下，根是柑橘幼苗中 NH 4 利用的主要器官。我们的结果表明，不同器官中 NH 4 浓度和酶活性的变化与根中比叶中更有效的 N 代谢有关，以防止常绿木本柑橘植物中的 NH 4 毒性。这些结果为柑橘植物利用 N 形式提供了深入了解，这对于 N 肥料管理很重要。
