State Key Laboratory of Tree Genetics and Breeding, School of Forestry, Northeast Forestry University, Harbin, 150040, PR China; Forestry College, Beihua University, Jilin, 132013, PR China.
Heilongjiang Academy of Forestry, Harbin, 150081, PR China.
Plant Physiol Biochem. 2020 Sep;154:530-537. doi: 10.1016/j.plaphy.2020.06.053. Epub 2020 Jul 17.
Populus species are fast growing with high N requirements; an optimum level of fertilization is necessary for high seedling quality and subsequent plantation productivity. In this study, the morphological and physiological responses of two poplar clones (XH and BL3) to exponential and conventional N dosages were investigated, with a specific focus on leaf traits, the photorespiratory N cycle, and the interconversion of amino acids within leaves. Results show that shoot height and leaf number exponentially increased with plant growth. Leaf area, chlorophyll concentration, and net photosynthetic rate significantly increased for both clones during N fertilization, with a significant difference only in leaf area of clone XH between exponential and conventional dosages. Leaf concentrations of free amino acids and soluble sugars were not different but soluble proteins and fatty acids were significantly different for clone XH between N dosages; the amino acids glutamate, alanine, and aspartic acid concentrations increased in exponentially fertilized seedlings compared to controls. Amino acids, including the composition concentration and activity of glutamic-oxalacetic and -pyruvic transaminase, and soluble sugars were significantly higher for clone BL3 in fertilized seedlings. Photorespiration (glycine and glycolate oxidase) and glutathione redox (oxidized glutathione) were affected by fertilization. The activities of key enzymes (glycolate oxidase, catalase, and γ-glutamate cysteine ligase) involved in photorespiration and glutathione metabolism were lower for clone XH with exponential fertilization. Phenylalanine catabolism was influenced by fertilization and the interaction, clone × fertilization, showing accumulation of phenylalanine and tyrosine but decreases in phenylalanine ammonialyase activity and flavonoid concentrations in leaves of fertilized seedlings. The results indicate that leaf area and the interconversion of amino acids through deamidation/transamination are key regulatory hubs in poplar acclimation to soil N availability.
杨属植物生长迅速，对氮的需求较高；为了保证幼苗质量和后续人工林的生产力，最佳施肥水平是必要的。本研究以两个杨树无性系（XH 和 BL3）为研究对象，探讨了指数施肥和常规施肥对杨树形态和生理特性的影响，重点关注叶片特性、光呼吸氮循环以及叶片内氨基酸的相互转化。结果表明，株高和叶片数随植株生长呈指数增长。在氮素供应过程中，两个无性系的叶面积、叶绿素浓度和净光合速率均显著增加，只有 XH 无性系的叶面积在指数施肥和常规施肥之间存在显著差异。游离氨基酸和可溶性糖在无性系间无差异，但在 XH 无性系中，可溶性蛋白和脂肪酸在氮素处理间存在显著差异；与对照相比，指数施肥下谷氨酸、丙氨酸和天冬氨酸的浓度增加。谷氨酸-草酰乙酸和 -丙酮酸转氨酶的组成浓度和活性以及可溶性糖等氨基酸在施肥的 BL3 无性系中显著较高。光合作用（甘氨酸和乙二醇氧化酶）和谷胱甘肽氧化还原（氧化型谷胱甘肽）受施肥影响。指数施肥下 XH 无性系的光呼吸（乙二醇氧化酶、过氧化氢酶和 γ-谷氨酰半胱氨酸连接酶）和谷胱甘肽代谢关键酶的活性较低。施肥影响苯丙氨酸分解代谢，且存在无性系与施肥的交互作用，表现为施肥后叶片中苯丙氨酸和酪氨酸积累，而苯丙氨酸氨裂解酶活性和类黄酮浓度降低。结果表明，叶片面积和通过脱酰胺/转氨基作用的氨基酸相互转化是杨树适应土壤氮供应的关键调节枢纽。
