王麗霞， 湯舉紅， 肖 斌， 楊亞軍， 柳 潔

(1 西北農(nóng)林科技大學(xué)園藝學(xué)院，陜西楊凌 712100； 2 長(zhǎng)江師范學(xué)院生命科學(xué)與技術(shù)學(xué)院，重慶涪陵 408000；3 中國(guó)農(nóng)業(yè)科學(xué)院茶葉研究所，浙江杭州 310013)

氟并不是植物的必需元素，植物吸氟后，會(huì)產(chǎn)生抑制光合[8]，引起細(xì)質(zhì)滲漏[9]，改變糖類和脂類的代謝，抑制酶活性[10]等生理作用。茶葉中的兒茶素類物質(zhì)如 EGCG、 EGC、 EC、 ECG是構(gòu)成茶葉品質(zhì)與風(fēng)味的主要成分，具有抗氧化活性[11]。茶氨酸和咖啡堿也是茶葉中天然存在的化合物，是兒茶素的合成前體[12]，可以刺激人體中樞神經(jīng)系統(tǒng)，提高人體的免疫能力[13]。茶葉的香氣主要由易揮發(fā)的芳香物質(zhì)構(gòu)成，是評(píng)價(jià)茶葉品質(zhì)優(yōu)良與否的重要指標(biāo)。茶葉的香氣成分受多種因素的影響，包括品種、 栽培條件、 環(huán)境因素和加工條件等。Yang等證明遮陰條件顯著影響茶葉的香氣成分[14]，張靈枝等證明不同的干燥方式也會(huì)對(duì)茶葉的香氣成分產(chǎn)生影響[15]。金屬元素鉀、 鈣、 鎂、 鐵和鋅既是植物生長(zhǎng)的必需元素，也是人體所需的營(yíng)養(yǎng)元素。研究葉片中這些營(yíng)養(yǎng)物質(zhì)在氟處理?xiàng)l件下含量的變化，有助于揭示氟對(duì)茶樹茶葉品質(zhì)的影響。因而，本試驗(yàn)擬通過茶苗的水培試驗(yàn)，研究營(yíng)養(yǎng)液中不同濃度氟對(duì)茶樹干物質(zhì)積累，相對(duì)生長(zhǎng)率，營(yíng)養(yǎng)元素吸收，葉片兒茶素類物質(zhì)和香氣組分的影響，初步探究氟影響茶葉生長(zhǎng)、 品質(zhì)及生理代謝的機(jī)理。

1 材料與方法

1.1 材料的培養(yǎng)

1.2 樣品的采集與測(cè)定

不同氟水平處理5周后收獲整株茶苗，先用自來水清洗3次后，再用去離子水沖洗一次。用濾紙吸干水分后，記錄植株鮮重及干重，計(jì)算相對(duì)生長(zhǎng)率(R)，R= (lnW2- lnW1)/(T2- T1)，其中W1和W2分別為時(shí)間T1和T2的整株干重，T2- T1為處理時(shí)間, 單位為g/(g·d)，DW。選取新長(zhǎng)出的頂部嫩葉、 嫩莖和根，洗凈后立刻用液氮超低溫保存或干燥后儲(chǔ)存在真空干燥器中，用于后續(xù)試驗(yàn)指標(biāo)的測(cè)定。

1.3 統(tǒng)計(jì)分析

用Excel進(jìn)行試驗(yàn)數(shù)據(jù)的基本計(jì)算，OriginPro 8.5.1軟件進(jìn)行統(tǒng)計(jì)分析，顯著水平分別為0.01和0.05(Fisher LSD方法)。

2 結(jié)果與分析

2.1 氟水平對(duì)茶苗生長(zhǎng)的影響

與對(duì)照相比，不同氟水平對(duì)茶苗根、 莖和葉干重的影響不同(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 氟水平下茶苗相對(duì)生長(zhǎng)率增加，比對(duì)照增加了8.8%，而0.2和0.3 mmol/L氟水平下茶苗相對(duì)生長(zhǎng)率分別降低了8.1%和15.5%。

表1 不同濃度氟對(duì)茶苗不同部位干物質(zhì)量和相對(duì)生長(zhǎng)率的影響Table 1 Effect of different fluoride contents on dry weight and relative growth rate of tea seedlings

注(Note): 同列數(shù)值后不同小寫字母表示處理間差異達(dá)5%顯著水平 Different lower letters at the same column mean significantly different at the 5% level.

2.2 不同濃度氟處理對(duì)茶苗葉片營(yíng)養(yǎng)元素含量的影響

不同氟水平處理對(duì)茶苗葉片不同營(yíng)養(yǎng)元素含量的影響不同(表2)。隨著氟處理濃度的增大，茶苗葉片氮、 鉀、 鎂、 鐵、 鋅與碳酸氫根的含量顯著降低，而磷、 鈣和氟的含量顯著增加，其中葉片氟的含量達(dá)到極顯著水平。氟處理對(duì)茶苗葉片中氯離子含量的影響不明顯。

2.3 不同濃度氟處理對(duì)茶苗葉片兒茶素、 茶氨酸、 咖啡堿含量的影響

隨著氟處理濃度的增大，葉片茶素類物質(zhì)的含量呈下降趨勢(shì)，除EGC的變化不明顯外，EC、 EGCG、 ECG的含量均顯著地下降了約20.7%、 23.5%、 50.4%(在0.3 mmol/L 氟處理下)。 此外，氟處理也顯著地降低了葉片茶氨酸和咖啡堿的含量，在0.2 mmol/L 氟處理下，茶氨酸降低了19.4%，咖啡堿降低了15.5%(表3)。

表2 氟處理對(duì)茶苗葉片營(yíng)養(yǎng)元素含量的影響Table 2 Effect of F treatments on nutrient element contents in tea leaves

注(Note): 同行數(shù)值后不同小寫字母表示處理間差異達(dá)5%顯著水平，大寫字母表示1%顯著水平 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 不同濃度氟處理對(duì)茶苗葉片香氣成分的影響

通過測(cè)定茶苗葉片香氣含量，共發(fā)現(xiàn)68種香氣成分(表4)。由于各種香氣成分的含量很低，本試驗(yàn)對(duì)葉片的香氣成分進(jìn)行了歸類，共分成烷類、 醛類、 醇類、 酯類、 酸類、 芳香、 酮類、 雜環(huán)、 胺類等9種；其中醛、 醇、 酯和芳香類是茶葉香氣物質(zhì)的主要成分。氟處理對(duì)這幾類物質(zhì)含量的影響不同(圖1)。對(duì)烷類、 酸類、 雜環(huán)類、 胺類和酮類物質(zhì)含量的影響不大，但對(duì)醛、 醇、 酯和芳香類物質(zhì)的影響較大，0.2 mmol/L F處理降低了葉片醛、 醇、 酯和芳香類物質(zhì)的含量，而0.3 mmol/L F處理增加了醛、 醇、 酯和芳香類物質(zhì)的含量。

表3 氟處理對(duì)葉片茶氨酸、 兒茶素和咖啡堿含量的影響(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—表沒食子兒茶素 Epigallocatechin; CAF—咖啡堿 Caffeine; EC—表兒茶素 Epicatechin; EGCG—表沒食子兒茶素沒食子酸酯 Epigallocatechin gallate; ECG—表兒茶素沒食子酸酯 Epicatechin gallate; 同列數(shù)值后不同小寫字母表示處理間差異達(dá)5%顯著水平 Different lower letters at the same column mean significantly different at the 5% level.

表4 不同濃度氟處理對(duì)茶苗葉片香氣成分含量的影響(mg/kg)Table 4 Effect of different fluoride concentrations on the leaf volatiles contents

續(xù)表4Table4continuos

香氣成分 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環(huán)辛醇 Cyclooctyl alcohol 0.0100.0110.0150.018反-氧化芳樟醇 Trans-Linalool oxide 0.2040.1160.2250.185戊基環(huán)丙烷 Cyclopropane, pentyl-0.0340.0420.0520.0472-(5-甲基-5-乙烯四氫呋喃-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-雙(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異亮氨酰絲氨酸 Ile-Ser0.0140.0090.0140.016水楊酸甲酯 Methyl salicylate3.3831.6111.7141.581alpha-松油醇 α-Terpineol0.0130.0160.0200.0221-甲基馬鞭草烯醇 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-亞甲基-6辛烯醇 6-Octen-1-ol, 7-methyl-3-methylene-0.0260.0230.0260.038

續(xù)表4Table4continuos

香氣成分 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香葉醇 Geraniol 0.1260.1130.1110.109(Z)-2-癸烯醛 2-Decenal, (Z)-0.0220.0170.0170.030水楊酸乙酯 Benzoic acid, 2-hydroxy-, ethyl ester0.3810.9240.7802.0902-1-亞乙基-1H-茚 1H-Indene, 1-ethylidene-0.0260.0120.0180.02111-氧雜四環(huán)十二烷-9-酮 11-Oxatetracyclo-dodecan-9-one0.0440.0230.0280.032(1-烯丙基環(huán)丙烷)甲醇 (1-Allylcyclopropyl)methanol0.0210.0240.0160.0226a-甲基-1,6-二環(huán)戊雙酮 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-5,9-十一雙烯-2-酮 5,9-Undecadien-2-one, 6,10-dimethyl-, (E)-——0.0090.0134甲基-1-(1-異丙基)-環(huán)己醇 Cyclohexanol, 4-methyl-1-(1-methylethyl)-0.0180.0190.0190.032反-α-紫羅酮 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): “—”表示未檢測(cè)出 Means no detected.

圖1 不同濃度氟對(duì)茶苗葉片香氣成分不同種類總量的影響 Fig.1 Effect of different fluoride contents on leaf volatile components in tea seedlings

3 討論

本試驗(yàn)中氟的短期處理(5周)降低了茶苗干物質(zhì)積累量和相對(duì)生長(zhǎng)率，但是與對(duì)照相比，未達(dá)到顯著效果，而在唐茜等[17]試驗(yàn)中，氟處理(19月)顯著降低了茶苗地上部干物質(zhì)量，這可能與氟處理時(shí)間有關(guān)。此外，也表明外源氟處理能抑制茶苗的生長(zhǎng)，這可能與氟抑制葉片正常的光合作用有關(guān)， Zwiazek and Shay[23]證明氟能夠破壞植物葉肉細(xì)胞的膜結(jié)構(gòu)，引起脂質(zhì)和葉綠體淀粉顆粒的滲漏，導(dǎo)致氣孔的非正常關(guān)閉，降低了葉片的光合性能，從而降低了植株的生長(zhǎng)和代謝能力。

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