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树木叶片衰老中的氮素再吸收机制研究进展

花匠小妙招
2025-01-03 06:18

摘要：

施加氮肥是保证人工农林生产的重要手段,但也带来生产成本增加和土壤、水体、大气污染等问题。提高植物的氮素利用效率是解决这一问题的关键途径。氮素利用效率是一个涉及遗传因素和环境因素互作的复杂性状,是植物根系对土壤氮素的吸收、植株对所吸收氮素的同化与利用、衰老组织/器官中氮素的再吸收等多方面效率的综合表现。氮素再吸收的步骤包括衰老源器官中蛋白质的降解、氨基酸转变以及韧皮部装载等环节,韧皮部装载被认为是衰老叶片氮素再吸收的限速环节。氮素再吸收通常与由发育年龄引发的整体植株或特定组织/器官的自然衰老或因环境胁迫诱导的提前衰老相偶联。再吸收衰老叶片中的氮素是多年生树木保守体内氮素、增强越冬抗胁迫能力的重要策略,其效率不仅与树种、树木年龄、树种功能类型(落叶或常绿、阔叶或针叶)等有关,也受生长环境、土壤氮素水平、水分供应等环境因子的影响。提高树木衰老叶片的氮素再吸收效率可降低树木下一季生长对外源氮肥的需求。由于有关树木叶片衰老和氮素再吸收机理的研究有限,未来应着重对调控树木叶片衰老的关键因子(如NAC、WRKY家族成员)、负责氨基酸向衰老叶片韧皮部装载的特定转运蛋白成员和介导脱落酸及乙烯等植物激素促进叶片衰老功能的信号元件进行鉴定,以此为通过遗传改良培育具有较高氮素利用效率的树木新品种提供可能的技术支持。

关键词: 树木, 叶片衰老, 氮素再吸收, 氮素利用效率, 调控机制

Abstract:

The application of nitrogen fertilizer is the main driving force for biomass production in artificial systems of agriculture and forestry. However, problems such as the increased cost and substantial pollution of soil, water and atmosphere are resulted from nitrogen leaching. Improving plant nitrogen use efficiency (NUE) is the crucial way to resolve these problems. NUE is a complex trait associated with an interplay between the genetic background and environmental factors, and is the comprehensive reflection of respective efficiencies with uptake of soil nitrogen by plant roots, assimilation and utilization of absorbed nitrogen inside plants, and resorption of nitrogen from senescent tissues or organs. The physiological steps of nitrogen resorption include a protein degradation in senescing organs,amino acid interconversion, and phloem loading of amino acids for remobilization. Phloem loading is thought to be the rate-limiting step of nitrogen resorption from senescing leaves. Nitrogen resorption is always accompanied with either natural senescence of the whole plant or certain tissues/organs determined by a developmental age or precocious senescence induced by environmental stresses. Nitrogen resorption in senescing leaves is an important strategy for perennial woody plants to conserve intrinsic nitrogen and increase stress tolerance through the winter season. The efficiency of nitrogen resorption is not only associated with species, age and functional types (i.e. deciduous or evergreen, broad- or needle-leaved) of woody plants, but also influenced by environmental factors such as geographic habitat, status of soil nitrogen and water supply. Improving efficiency of nitrogen resorption from senescing leaves may alleviate the requirement of trees for nitrogen fertilizer in the next growth season. As studies about mechanisms of leaf senescence and nitrogen resorption in trees are rare at present, characterization of key factors (such as NAC and WRKY family members) regulating leaf senescence, certain transporters responsible for phloem loading of amino acids in senescing leaves and signaling components mediating functions of phytohormones (such as abscisic acid and ethylene) which may promote leaf senescence is desired in woody plants in coming years, thus providing putative technological supports for breeding tree cultivars with the improved NUE through the genetic modification.

Key words: woody plants, leaf senescence, nitrogen resorption, nitrogen use efficiency, regulatory mechanism

中图分类号:

Q945.48

S718