摘要
【目的】氮素是茶树生长发育过程中必需的营养元素,其供应水平影响茶叶碳氮代谢平衡。探究不同氮肥施用量对茶树叶片碳氮代谢的调控效应,对茶叶实际生产具有理论价值与实践意义。【方法】以长势均匀一致的‘白叶一号’茶树为材料,采用盆栽试验,设置不施氮N0(0 g/kg)、低氮(N1,0.375 g/kg)、中氮(N2,0.75 g/kg)和高氮(N3,1.125 g/kg)4个氮肥水平,研究不同氮肥施用量下‘白叶一号’茶树叶片碳氮代谢相关生化指标的变化,分析氮肥施用量与茶树碳氮代谢之间的相关性。【结果】氮肥施用量通过影响茶树叶片关键酶活性,改变了碳氮代谢流的分配方向。低氮(N1)条件下,苯丙氨酸解氨酶(PAL)与磷酸烯醇式丙酮酸羧化酶(PEPC)活性最高,驱动碳流显著偏向苯丙烷代谢途径,促进茶多酚、表没食子儿茶素(EGC)、表儿茶素(EC)及游离氨基酸的合成,同时抑制氮同化关键酶[谷氨酰胺合成酶(GS)、硝酸还原酶(NR)、谷氨酸脱氢酶(GDH)]活性。中氮(N2)条件下,GS、NR、GDH活性达到峰值,说明氮同化效率最大,此时碳资源主要用于氮同化过程及叶绿素合成,导致全氮积累增加,而茶多酚、儿茶素总量显著降低。高氮(N3)条件下,GS、NR、GDH活性下降,氮同化效率降低,但谷氨酸合成酶(GOGAT)活性持续上升至最高,此时代谢特征表现为碳流转向渗透调节物质合成,导致可溶性糖与咖啡碱含量显著升高;同时PAL活性持续受抑,茶多酚含量降至最低,而全氮积累达到峰值。相关性分析进一步证实,氮肥施用量与PAL、茶多酚、EGC、EC呈显著负相关,与GOGAT、NR、GDH、全氮、可溶性糖、咖啡碱呈显著正相关。主成分分析显示,氮肥对全氮、全磷、可溶性糖、EGC、茶多酚、游离氨基酸及PAL、PEPC活性影响最显著。【结论】PAL、GS/GOGAT/GDH/NR分别是调控碳流向酚类防御代谢与氮同化效率的核心节点,其活性随供氮水平的变化而变化,进而决定了碳氮资源在生长、防御及胁迫响应之间的平衡分配。因此,适量施氮有助于维持茶树体内碳氮代谢动态平衡,对增加氮肥利用效率、提升茶叶产量和品质具有重要作用,是实现茶叶优质高产的重要路径。
【Objectives】Nitrogen is an indispensable nutrient for tea plant growth and development,and its supply significantly influeces the balance of carbon and nitrogen metabolism in tea leaves.This study aimed to explor the effects of different nitrogen fertilizer application rates on carbon and nitrogen metabolism in tea plant,providing theoretical and practical insights for optimizing tea production.【Methods】A pot experiment was set up with four nitrogen fertilizer application rates:no nitrogen N0(0 g/kg),low nitrogen N1(0.375 g/kg),medium nitrogen N2(0.75 g/kg)and high nitrogen N3(1.125 g/kg).Changes of carbon and nitrogen metabolism related biochemical indexes in the leaves of‘Baiye 1’tea tree under different nitrogen fertilizer application rates were measured,and the correlation between nitrogen fertilizer application rate and carbon and nitrogen metabolism of tea plants was analyzed.【Results】Nitrogen fertilizer application rates significantly affected the activities of key enzymes in tea leaves,which profoundly changed the distribution direction of carbon and nitrogen metabolism flow.Under low nitrogen conditions(N1),phenylalanine ammonia lyase(PAL)and phosphoenolpyruvate carboxylase(PEPC)had the highest activities,driving carbon flow toward the phenylpropane metabolism pathway and promoting the synthesis of tea polyphenols,catechin components epigallocatechin(EGC),epicatechin(EC)and free amino acids,and inhibiting the activities of key enzymes of nitrogen assimilation(glutamine synthase(GS),nitrate reductase(NR)and glutamate dehydrogenase(GDH)).Under medium nitrogen conditions(N2),the activities of GS,NR,GDH reached their peaks,indicating that the nitrogen assimilation efficiency was maximized.At this time,carbon resources were mainly used for nitrogen assimilation and chlorophyll synthesis,resulting in an increase in total nitrogen accumulation and a significant decrease in the total amount of tea polyphenols and catechins.Under high nitrogen conditions(N3),the activities of GS,NR and GDH decreased,and the nitrogen assimilation efficiency decreased,but the activity of glutamate synthase(GOGAT)continued to rise to the highest.At the same time,PAL activity continued to be suppressed,the content of tea polyphenols was minimized,and the total nitrogen accumulation reached its peak.Correlation analysis further confirmed that the application rate of nitrogen fertilizer was significantly negatively correlated with PAL,tea polyphenols,EGC and EC,and positively correlated with GOGAT,NR,GDH,total nitrogen,soluble sugar and caffeine.Principal component analysis showed that nitrogen fertilizer had the most significant effects on total N,total P,soluble sugar,EGC,tea polyphenols,free amino acids,PAL and PEPC activities.【Conclusions】PAL,GS/GOGAT/GDH/NR are the core nodes that regulate the metabolism and nitrogen assimilation efficiency of carbon flow to phenolic defense,respectively,and their activities change with nitrogen supply levels and determine the allocation balance between growth,defense and stress response.Therefore,appropriate nitrogen application can help to maintain the dynamic balance of carbon and nitrogen metabolism in tea plants,which is important for increasing nitrogen fertilizer use efficiency and improving tea yield and quality.
作者
韩二玲
秦永龙
王兴飘
谷勋刚
HAN Er-ling;QIN Yong-long;WANG Xing-piao;GU Xun-gang(College of Resources and Environment,Anhui Agricultural University,Hefei,Anhui 230036,China)
出处
《植物营养与肥料学报》
北大核心
2025年第9期1819-1829,共11页
Journal of Plant Nutrition and Fertilizers
基金
国家自然科学基金项目(31770729)
安徽省科技重大专项(202103b06020024)
安徽虫虫生物科技有限公司重点研发项目(KJ2021092)。
关键词
氮肥施用量
茶树
碳氮代谢
nitrogen fertilizer application rate
tea plant
carbon and nitrogen metabolism
