施氮对茶树叶片光合作用的影响及氮、碳代谢调控机制研究

At present blind application of a large number of nitrogen fertilizer in tea plantation has not only seriously affected the quality of tea, but also resulted in wasting of resources and environmental degradation. So far as, the mechanisms on nitrogen and carbon response and how nitrogen affects the quality of tea tree under nitrogen-stress have not been studied. In this study, we had screened relatively high and low nitrogen-utility germplasm from the tea cultivars of Fujian province. The following aspects have also investigated: ①Effect of photosynthesis system、chlorophyll fluorescence、nitrogen concent、active oxygen metabolism under different supplying nitrogen were analyzed. ② Effect of tea growth、key enzyme content of nitrogen assimilation(nitrate reductase NR, nitrite reductase NiR, glutamine synthetase GS and glutamate synthase GOGAT) were analyzed. ③Effect of carbon metabolism (RuBP carboxylase, sucrose phosphorus synthase SPS, sucrose synthase SS and invertase Inv) were analyzed. ④Effect of dry matter accumulation and key enzyme of carbon and nitrogen metabolism were analyzed. The main objective of this study was to understand effect of photosynthesis system and metabolic mechanism of carbon and nitrogen. The main objective was providing scientific basis high yield and high quality cultivation of tea plant.

目前茶园中盲目的施用大量氮肥，严重影响茶叶的品质，造成资源浪费，生态环境恶化。而关于施氮对茶树生理响应机制、碳与氮代谢调控机制、氮素如何影响茶叶品质尚未阐明。本研究以前期筛选出的氮高效与氮敏感型的茶树幼苗为试验材料，探明不同施氮水平对①茶树叶片光合特性、叶绿素荧光特性、叶片氮素含量、活性氧代谢的影响，阐明不同施氮下限制光合速率的主要因素；②茶树生长、氮素同化关键酶（硝酸还原酶 NR、亚硝酸还原酶 NiR、谷氨酰胺合成酶 GS 和谷氨酸合酶 GOGAT）活力的变化规律及相关关系的影响；③茶树叶片碳代谢关键酶（RuBP 羧化酶、蔗糖磷素合成酶(SPS)、蔗糖合成酶(SS) 和转化酶 (Inv)）的影响；④茶树体内干物质积累的变化规律进行分析，探讨碳、氮代谢关键指标对茶树产质量的影响。旨在明确不同施氮水平对茶树叶片光合作用影响及茶树氮、碳代谢的机制，为茶树高产优质栽培提供科学依据。

茶树是种植在热带、亚热带的叶用植物。氮是提高茶叶品质最重要的营养元素之一，氮肥施用引起人们广泛的关注。研究表明，(1)缺氮显著降低茶树叶片CO2同化速率、气孔导度，却使得胞间CO2浓度显著增加，说明茶树缺氮下CO2同化速率下降由非气孔因素引起；缺N下，叶片初始和总Rubisco活性、Chl和总的可溶性蛋白质含量下降的幅度均低于CO2同化下降的幅度，缺N降低叶片蔗糖、淀粉、葡萄糖、果糖的含量。缺氮叶片Fv/Fm, REo/ETo, ETo/ABS, Sm，ETo/CSo, PIabs, PItot, abs显著下降，但是热耗散参数DIo/CSo, DIo/RC and DIo/ABS显著增加。回归分析发现缺氮叶片CO2同化速率下降主要由Chl、PIabs、初始Rubisco活性下降引起的。(2)缺氮下茶树叶片丙二醛（MDA）含量与H2O2产生速率有所增加，且本山品种增加的尤为显著。缺氮下除超氧物岐化酶（SOD）活性显著增加外，其余抗氧化酶[过氧化物酶（POD）、过氧化氢酶（CAT）、谷胱甘肽还原酶（GR）等]活性和抗氧化物质[还原型谷胱甘肽（GSH）、抗坏血酸（ASC）]含量都下降，其中黄旦品种的抗氧化酶活性和抗氧化物质含量大部分都高于或与本山相似，说明耐低氮品种黄旦缺氮环境下能更好调节保护自身，免受伤害，更好的适应缺氮环境。(3)缺氮下茶树叶片水浸出物、茶多酚、酚氨比与总儿茶素都显著的增加，而游离氨基酸总量、茶氨酸和谷氨酸显著降低。研究表明，供氮各处理下，本山品种叶片游离氨基酸和多酚含量低于黄旦品种，而水浸出物两品种相当。随着供氮增加，茶树叶片挥发性物质己醛、2,4-二烯醛、癸烯醛、丁烯、三甲基环己烯、叶绿醇等依次显著增加，而罗勒烯、芳樟醇、环柠檬醛、十四烷、十五烷、柠檬烯、十二烷等含量显著降低。缺氮降低氨基酸含量等鲜爽滋味含量，增加茶多酚、儿茶素等苦涩味含量，因此缺氮茶叶感官品质显著下降。(4)缺氮下茶树叶片NR、NiR、NADH-GOGAT活性显著降低，然而GS的活性却显著增加，黄旦叶片NR的活性显著高于本山品种。NiR、NADH-GOGAT、GS活性在供氮范围内两品种基本未见明显差异。供氮下，根系NR活性变化不大，NiR与NADH-GOGAT活性缺氮下显著下降，两品种间未见显著差异。