氟对茶树生长叶片营养元素含量、 儿茶素类物质和香气成分的影响

王丽霞， 汤举红， 肖 斌， 杨亚军， 柳 洁

(1 西北农林科技大学园艺学院，陕西杨凌 712100； 2 长江师范学院生命科学与技术学院，重庆涪陵 408000；3 中国农业科学院茶叶研究所，浙江杭州 310013)

氟并不是植物的必需元素，植物吸氟后，会产生抑制光合[8]，引起细质渗漏[9]，改变糖类和脂类的代谢，抑制酶活性[10]等生理作用。茶叶中的儿茶素类物质如 EGCG、 EGC、 EC、 ECG是构成茶叶品质与风味的主要成分，具有抗氧化活性[11]。茶氨酸和咖啡碱也是茶叶中天然存在的化合物，是儿茶素的合成前体[12]，可以刺激人体中枢神经系统，提高人体的免疫能力[13]。茶叶的香气主要由易挥发的芳香物质构成，是评价茶叶品质优良与否的重要指标。茶叶的香气成分受多种因素的影响，包括品种、 栽培条件、 环境因素和加工条件等。Yang等证明遮阴条件显著影响茶叶的香气成分[14]，张灵枝等证明不同的干燥方式也会对茶叶的香气成分产生影响[15]。金属元素钾、 钙、 镁、 铁和锌既是植物生长的必需元素，也是人体所需的营养元素。研究叶片中这些营养物质在氟处理条件下含量的变化，有助于揭示氟对茶树茶叶品质的影响。因而，本试验拟通过茶苗的水培试验，研究营养液中不同浓度氟对茶树干物质积累，相对生长率，营养元素吸收，叶片儿茶素类物质和香气组分的影响，初步探究氟影响茶叶生长、 品质及生理代谢的机理。

1 材料与方法

1.1 材料的培养

1.2 样品的采集与测定

不同氟水平处理5周后收获整株茶苗，先用自来水清洗3次后，再用去离子水冲洗一次。用滤纸吸干水分后，记录植株鲜重及干重，计算相对生长率(R)，R= (lnW2- lnW1)/(T2- T1)，其中W1和W2分别为时间T1和T2的整株干重，T2- T1为处理时间, 单位为g/(g·d)，DW。选取新长出的顶部嫩叶、 嫩茎和根，洗净后立刻用液氮超低温保存或干燥后储存在真空干燥器中，用于后续试验指标的测定。

1.3 统计分析

用Excel进行试验数据的基本计算，OriginPro 8.5.1软件进行统计分析，显著水平分别为0.01和0.05(Fisher LSD方法)。

2 结果与分析

2.1 氟水平对茶苗生长的影响

与对照相比，不同氟水平对茶苗根、 茎和叶干重的影响不同(表1)。0.1 mmol/L 氟水平下茶苗干重增加了3%，而0.2和0.3 mmol/L氟水平下茶苗干重降低了2.1% 和 6.4%；0.1 mmol/L 氟水平下茶苗相对生长率增加，比对照增加了8.8%，而0.2和0.3 mmol/L氟水平下茶苗相对生长率分别降低了8.1%和15.5%。

表1 不同浓度氟对茶苗不同部位干物质量和相对生长率的影响Table 1 Effect of different fluoride contents on dry weight and relative growth rate of tea seedlings

注(Note): 同列数值后不同小写字母表示处理间差异达5%显著水平 Different lower letters at the same column mean significantly different at the 5% level.

2.2 不同浓度氟处理对茶苗叶片营养元素含量的影响

不同氟水平处理对茶苗叶片不同营养元素含量的影响不同(表2)。随着氟处理浓度的增大，茶苗叶片氮、 钾、 镁、 铁、 锌与碳酸氢根的含量显著降低，而磷、 钙和氟的含量显著增加，其中叶片氟的含量达到极显著水平。氟处理对茶苗叶片中氯离子含量的影响不明显。

2.3 不同浓度氟处理对茶苗叶片儿茶素、 茶氨酸、 咖啡碱含量的影响

随着氟处理浓度的增大，叶片茶素类物质的含量呈下降趋势，除EGC的变化不明显外，EC、 EGCG、 ECG的含量均显著地下降了约20.7%、 23.5%、 50.4%(在0.3 mmol/L 氟处理下)。 此外，氟处理也显著地降低了叶片茶氨酸和咖啡碱的含量，在0.2 mmol/L 氟处理下，茶氨酸降低了19.4%，咖啡碱降低了15.5%(表3)。

表2 氟处理对茶苗叶片营养元素含量的影响Table 2 Effect of F treatments on nutrient element contents in tea leaves

注(Note): 同行数值后不同小写字母表示处理间差异达5%显著水平，大写字母表示1%显著水平 Different small letters at the same row mean significantly different at the 5% level and capital letters mean significantly different at the 1% level.

2.4 不同浓度氟处理对茶苗叶片香气成分的影响

通过测定茶苗叶片香气含量，共发现68种香气成分(表4)。由于各种香气成分的含量很低，本试验对叶片的香气成分进行了归类，共分成烷类、 醛类、 醇类、 酯类、 酸类、 芳香、 酮类、 杂环、 胺类等9种；其中醛、 醇、 酯和芳香类是茶叶香气物质的主要成分。氟处理对这几类物质含量的影响不同(图1)。对烷类、 酸类、 杂环类、 胺类和酮类物质含量的影响不大，但对醛、 醇、 酯和芳香类物质的影响较大，0.2 mmol/L F处理降低了叶片醛、 醇、 酯和芳香类物质的含量，而0.3 mmol/L F处理增加了醛、 醇、 酯和芳香类物质的含量。

表3 氟处理对叶片茶氨酸、 儿茶素和咖啡碱含量的影响(mg/g， DW)Table 3 Effect of F on the contents of catechins, theanine and caffeine in tea leaves

注(Note): THE—茶氨酸 Theanine; EGC—表没食子儿茶素 Epigallocatechin; CAF—咖啡碱 Caffeine; EC—表儿茶素 Epicatechin; EGCG—表没食子儿茶素没食子酸酯 Epigallocatechin gallate; ECG—表儿茶素没食子酸酯 Epicatechin gallate; 同列数值后不同小写字母表示处理间差异达5%显著水平 Different lower letters at the same column mean significantly different at the 5% level.

表4 不同浓度氟处理对茶苗叶片香气成分含量的影响(mg/kg)Table 4 Effect of different fluoride concentrations on the leaf volatiles contents

续表4Table4continuos

香气成分 The aroma compountsCK0.1 mmol/L F0.2 mmol/L F0.3 mmol/L F6-甲基-5-庚烯-2-酮 5-Hepten-2-one, 6-methyl-——0.0120.0162-正戊基呋喃 Furan, 2-pentyl-0.0190.0190.0220.0272-甲基-6-庚烯醇 6-Hepten-1-ol, 2-methyl-0.1090.1080.1420.152cis-2-(2-戊烯基)呋喃 Cis-2-(2-Pentenyl)furan0.019———3-己酸乙酯 3-Hexenoic acid, ethyl ester—0.0200.0260.0533-甲基-3-庚醇 3-Heptanol, 3-methyl-0.0150.0110.0140.030(E,E)-2,4-庚二烯醛 2,4-Heptadienal, (E,E)-0.0200.0220.0260.0392-乙基-4甲基-戊醇 1-Pentanol, 2-ethyl-4-methyl-0.0270.0170.0290.024苯甲醇 Benzyl alcohol0.3300.4000.4090.709苯乙醛 Benzeneacetaldehyde0.0110.0120.0150.0283-己酸乙酯 2-Hexenoic acid, ethyl ester———0.041(E)-2-辛烯醛 2-Octenal, (E)-———0.013环辛醇 Cyclooctyl alcohol 0.0100.0110.0150.018反-氧化芳樟醇 Trans-Linalool oxide 0.2040.1160.2250.185戊基环丙烷 Cyclopropane, pentyl-0.0340.0420.0520.0472-(5-甲基-5-乙烯四氢呋喃-2-yl)丙烷-2-ly-碳酸乙酯 Ethyl-2-(5-methyl-5-vinyltetrahydrofuran-2-yl)propan-2-yl carbonate0.2620.1750.1990.2703,3-二甲基-庚烷 Heptane, 3,3-dimethyl-———0.010芳樟醇 1, 6-Octadien-3-ol, 3,7-dimethyl-1.4981.6222.2142.618壬醛 Nonanal0.0400.0340.0420.048苯乙醇 Phenylethyl Alcohol0.1670.1160.2240.3202-硝基苯酚 Phenol, 2-nitro-0.0200.0150.0270.0294-甲基-癸烷 Decane, 4-methyl-0.0110.0120.0180.0191,1-双(十二烷氧基)-十六烷 Hexadecane, 1,1-bis(dodecyloxy)-0.0150.0130.0230.0212,3-二甲基癸烷 2,3-Dimethyldecane0.0220.0240.0260.0271-乙基-2(1H)吡啶 2(1H)-Pyridinone, 1-ethyl-0.0110.0100.0140.0241-癸醇 1-Decanol0.0310.0300.0520.048异亮氨酰丝氨酸 Ile-Ser0.0140.0090.0140.016水杨酸甲酯 Methyl salicylate3.3831.6111.7141.581alpha-松油醇 α-Terpineol0.0130.0160.0200.0221-甲基马鞭草烯醇 1-Methylverbenoll0.0150.0140.010—辛酸乙酯 Octanoic acid, ethyl ester———0.0255-乙基癸烷 5-Ethyldecane—0.0130.0170.021癸醛 Decanal 0.0130.0150.0220.0277-甲基-3-亚甲基-6辛烯醇 6-Octen-1-ol, 7-methyl-3-methylene-0.0260.0230.0260.038

续表4Table4continuos

香气成分 The aroma compountsCK0.1 mmol/L F0.2 mmol/L F0.3 mmol/L F橙花醇 2,6-Octadien-1-ol, 3,7-dimethyl-, (Z)-0.0610.0590.0690.082(Z)-3,7-二甲基-3,6-辛二烯醇3,6-Octadien-1-ol, 3,7-dimethyl-, (Z)-0.0370.0330.0400.0432-硝基-4-甲苯酚 Phenol, 4-methyl-2-nitro-0.0100.0090.0200.014香叶醇 Geraniol 0.1260.1130.1110.109(Z)-2-癸烯醛 2-Decenal, (Z)-0.0220.0170.0170.030水杨酸乙酯 Benzoic acid, 2-hydroxy-, ethyl ester0.3810.9240.7802.0902-1-亚乙基-1H-茚 1H-Indene, 1-ethylidene-0.0260.0120.0180.02111-氧杂四环十二烷-9-酮 11-Oxatetracyclo-dodecan-9-one0.0440.0230.0280.032(1-烯丙基环丙烷)甲醇 (1-Allylcyclopropyl)methanol0.0210.0240.0160.0226a-甲基-1,6-二环戊双酮 6a-Methyl-hexahydropentalene-1,6-dione0.0150.0120.0100.019正十四烷 Tetradecane0.0100.0180.0140.0181,5-二甲基-萘 Naphthalene, 1,5-dimethyl-0.009———(E)-6,10-二甲基-5,9-十一双烯-2-酮 5,9-Undecadien-2-one, 6,10-dimethyl-, (E)-——0.0090.0134甲基-1-(1-异丙基)-环己醇 Cyclohexanol, 4-methyl-1-(1-methylethyl)-0.0180.0190.0190.032反-α-紫罗酮 Trans-α-Ionone0.015———正十五烷 Pentadecane——0.0090.013石竹素 Caryophyllene oxide0.0180.0190.0190.0323,7,11-三甲基-1,6,10-十二烷三烯-3-醇 1,6,10-Dodecatrien-3-ol, 3,7,11-trimethyl-0.0200.0230.0270.030十六烷 Hexadecane0.0210.0260.0340.040

注(Note): “—”表示未检测出 Means no detected.

图1 不同浓度氟对茶苗叶片香气成分不同种类总量的影响 Fig.1 Effect of different fluoride contents on leaf volatile components in tea seedlings

3 讨论

本试验中氟的短期处理(5周)降低了茶苗干物质积累量和相对生长率，但是与对照相比，未达到显著效果，而在唐茜等[17]试验中，氟处理(19月)显著降低了茶苗地上部干物质量，这可能与氟处理时间有关。此外，也表明外源氟处理能抑制茶苗的生长，这可能与氟抑制叶片正常的光合作用有关， Zwiazek and Shay[23]证明氟能够破坏植物叶肉细胞的膜结构，引起脂质和叶绿体淀粉颗粒的渗漏，导致气孔的非正常关闭，降低了叶片的光合性能，从而降低了植株的生长和代谢能力。

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