阿里山不同海拔茶菁內容物變化與成因初探

Abstract

氣候變遷造成的環境因子變動對茶葉生產影響甚鉅，也同時影響茶菁內容物的組成，進而影響成茶品質。阿里山為臺灣高山茶重要茶區，茶園位於海拔800公尺至1600公尺區間，且是雲霧帶的分布區域。在阿里山茶區中，海拔高度與地理環境的共同影響使得同一氣候區下各茶園可能有不同的微氣候環境。為探討不同海拔茶區氣候因子對茶菁內容物組成差異的效應及可能成因，本研究分為三個部分進行。第一部分為標定大阿里山茶區不同海拔共14座阿里山茶園，分析各茶園土壤養分、植體礦物養分及2022年春茶茶菁中兒茶素、咖啡因、總游離胺基酸等內容物含量，並由架設於各茶園的微氣象站所蒐集之氣溫、光量子通量、相對溼度等為氣象因子參數，探討茶菁在不同環境下內容物的組成及變化。分析結果顯示茶菁中總游離胺基酸含量與EGCG呈負相關 (r = -0.68*)，茶菁採摘前21日的氣象條件為茶菁中兒茶素異構物組成比例的關鍵區間，酯型兒茶素含量與氣溫為高度正相關 (r = 0.81**)，而與相對濕度呈現負相關 (r = -0.57*)。以氣溫與光積值為參數對茶園樣區進行群集分析，茶園樣區可分為四群，氣溫為主要分群因子，在20℃以下的栽培環境中，溫度增加會使酯型兒茶素含量比例提高，氣溫18℃為酯型兒茶素含量變化的關鍵溫度；光積值為次要分群因子，自然光強度對兒茶素含量的影響則不如氣溫顯著。阿里山茶區經常出現雲霧，雲霧會改變氣溫與光強度，提高散射光比例及改變紅藍光的組合比例，因此設計不同光照與氣溫的試驗進行討論。第二部分以兩個日夜溫環境20/15℃、30/25℃，分別進行0%、50%、80%三個程度連續遮陰處理14日，探討溫度與光度對茶菁內容物的影響。結果顯示栽培於20℃的植株嫩梢較30℃有更高的總兒茶素含量，含量隨光強度降低而減少，咖啡因不受溫度影響，但在低光度下會累積。溫度與光度對兒茶素的累積具有交感效應。第三部分以人工光盤設定單光質紅光、單光質藍光、紅藍光2:1 (RRB)、紅藍光1:2 (RBB) 4種光質處理茶樹7日並分析嫩梢內容物，結果顯示EGC的含量隨藍光比例增加先升後降，在組合光質紅光200 μmol∙m-2∙s-1、藍光100 μmol∙m-2∙s-1處理下有最高的含量。本研究初步探討氣溫、光度與光質對茶菁中兒茶素含量的個別效應，將可做為日後因應氣候變遷維持茶菁良好品質管理策略的參考基礎。

Tea quality is determined by the composition of tea shoot content, which is influenced by environmental factors. Climate change has resulted in significant alterations to environmental factors, thereby exerting a substantial impact on tea production. Alishan, a crucial tea-producing region in Taiwan, includes tea fields situated between 800 meters and 1600 meters above sea level, within the cloud belt zone. Variances in altitude and geographical features contribute to distinct microclimates within the same climatic zone. To assess the effects of environmental factors at different altitudes on tea shoot content, this study was conducted in three parts. In the first part, fourteen Alishan tea fields at varying altitudes were selected to analyze soil properties, plant nutrition, and tea shoot components, such as catechins, caffeine, and total free amino acids, during the spring of 2022. Meteorological data, including temperature, photosynthetic photon flux density, and relative humidity, were collected using mini weather stations. The analysis results showed a negative correlation between the total free amino acid content and EGCG in tea shoots (r = -0.68*). The meteorological conditions 21 days before tea shoot picking were found to be a critical period for the composition ratio of catechin isomers in tea shoots. The content of esterified catechins was highly positively correlated with temperature (r = 0.81**), while it showed a negative correlation with relative humidity (r = -0.57*). Cluster analysis was conducted on tea field plots using temperature and daily light integral as parameters, resulting in four clusters. Temperature was identified as the primary clustering factor; in cultivation environments below 20℃, an increase in temperature led to a higher proportion of esterified catechins. The temperature of 18℃ was identified as the critical temperature for the variation in esterified catechin content. Daily light integral was identified as the secondary clustering factor, with sunlight intensity having a less significant impact on catechin content compared to temperature. Clouds and fog are frequently observed in the Alishan tea production area, which can alter temperature and light intensity, increasing the proportion of scattered light and modifying the combination ratio of red and blue light. Therefore, experiments were designed to discuss the effects of different light and temperature conditions. In the second part, experiments were conducted under two day-night temperature regimes, 20/15℃ and 30/25℃, with shading treatments of 0%, 50%, and 80% for 14 days each, to investigate the influence of temperature and light intensity on the contents of tea shoots. Results indicated that plants cultivated at 20℃ had higher total catechin content compared to those at 30℃, with the content decreasing as light intensity decreased. Caffeine was not affected by temperature but accumulated under low light conditions. A synergistic effect of temperature and light intensity was found on catechin accumulation. In the third part, artificial light sources were used in four light quality treatments: pure red light, pure blue light, a red-blue light ratio of 2:1 (RRB), and a red-blue light ratio of 1:2 (RBB), for 7 days. Results demonstrated that the EGC content initially increased with a rise in the proportion of blue light, particularly at the peak of red light 200 μmol∙m-2∙s-1 and blue light 100 μmol∙m-2∙s-1 treatment. Overall, this study provides preliminary insights into the individual effects of temperature, light intensity, and light quality on catechin content in tea shoots, offering valuable strategies for maintaining tea shoot quality under climate change.