細葉山茶(Camellia tenuifolia (Hay.) Coh.)生長發育及種子油成分之季節性變動

Abstract

細葉山茶Camellia tenuifolia (Hay.) Coh. 為原生於台灣北部、中部闊葉林地之茶科山茶屬小型喬木，種子所榨成的油品俗稱苦茶油。由於細葉山茶種子含油率及油質成份會隨生長過程變動，因此藉由調查其基本生長特性與週期，並分析發育過程中種子油含量與成分的變化，可得知果實最適宜的採收成熟度，以供將來生產應用。細葉山茶枝梢前端節位的芽常為混合芽，其中的副芽可經花芽創始與分化形成花芽。根據觀測其發育過程中內部花器及外觀的變化，將花芽發育細分並定義為16個階段(Stage)。Stage 2-6陸續形成花被、雄蕊、雌蕊原基，此時花芽長寬各小於6 mm和3 mm，需歷時2-3個月；至Stage 7-16花藥、花柱、子房等花器逐漸成熟、花瓣的轉色以及開花，需歷時1-2個月。若花芽在Stage 12以上，長寬各大於 8 mm和5 mm時，約2-3週後即可開花。整個花芽形成須歷時4-5個月。細葉山茶果實成熟需一年的時間。調查果徑、果高、果實鮮重可知其屬於雙S型的生長曲線。胚的總直徑及果皮厚度變化則分別為雙S型與單S型的生長曲線。成熟果實果徑及果高約2 cm，果實鮮重約4.5 g，果實心皮數以三個最多、四個次之，五個心皮則較少，單一心室內多半僅有一顆種子，而單顆果實內種子數以兩個最多、三個次之。根據觀察細葉山茶之生育週期得知其一年可抽出三次梢，三月時抽出春梢，春梢及前一年抽出之冬梢上的花芽於五月分化完成並開始發育，花芽敗育的節位在六月抽出夏梢並隨即進行花芽分化及發育。十月為盛花期與著果期，著果初期的花後10-30天易落果，隔年一月進入第一次快速生長期，而三、四月為果實生長停滯期，直到五月進入第二次快速生長期，此時果實大小與重量均大幅增加，九到十一月則是果實成熟期。隨著種子發育含水率逐漸下降。種子含油隨果實成熟度提高而增加，成熟之乾種仁含油率達40.50±0.71%，油酸、亞麻油酸、棕櫚酸等脂肪酸在單顆種子中的含量均上升; 但以細葉山茶苦茶油中的組成比例來看，油酸及亞麻油酸所占的比例隨種子成熟度提高而上升，棕櫚酸則降低。最終，細葉山茶苦茶油的主要脂肪酸組成比例為油酸(C18:1) 72.33±0.89%，亞麻油酸(C18:2) 13.39±1.10%及棕櫚酸(C16:0) 10.19±0.11%。由以上資料顯示，若欲得到較高含油率之果實與榨得具有較高比例不飽和脂肪酸之苦茶油，細葉山茶果實在台灣北部的最佳採收時機應為九月下旬至十一月間。

Camellia tenuifolia (Hayata) Coh.-Stuart is an endemic shrub of the Theaceae family native to the evergreen broadleaf forest in northern and central Taiwan. The oil extracted from the seeds is called camellia tea seed oil. According to the oil content and nutrient component change throughout the fruit growth process, this study attempts to look in to the basic growth characteristics and analyze the composition of C. tenuifolia seeds in order to establish optimum harvest timing for commercial production. Terminal buds and upper axillary buds are usually mixed buds. The accessory buds among mixed buds can develop into flower buds after initiating. Based on the observation, the flower developing stage can be divided into 16 stages. Perianth primordia, stamen primordia and carpel primodia take 2-3 months to organize in stage 2-6, when the length and width of flower buds are less than 6 and 3 mm. Flowers mature, color and bloom in stage 7-16, which takes 1-2 months. After stage 12, length and width of flower buds become greater than 8 and 5 mm, with the flowers ready to bloom in 2-3 weeks. The whole flower developing process takes 4-5 months for flower development. C. tenuifolia fruit needs one year to grow. The fruit diameter, height, fresh weight and total seed diameter growth patterns fit a double sigmoid growth curve during fruit development, while the pericarp thickness growth pattern fits a single sigmoid growth curve. One mature fruit weighs around 4.5 g, and is about 2 cm in diameter and height. Each fruit has maybe 3-5 carpels and most of the fruits have 2-3 seeds. There is only 1 seed in most carpels. C. tenuifolia shoots three times a year. Spring shoots grow in March, and flower buds of spring shoots and winter shoots from the previous year start to develop in May. Summer shoots will grow on the nodes where flower buds abort. Full bloom and fruit set stage start in October. Abundant fruit drop occurs in 10-30 days after flowering. The first rapid growth period starts in January, and is followed by the suspended growth period in March to April. Fruit grow and the size increases rapidly starting from May, and reaches maturity in September to November. Along with seeds maturation, moisture decreases but the total oil content, amount of oleic acid (C18:1), linoleic acid (C18:2) and palmic acid (C16:0) increases. However, the percentage of palmic acid among camellia tea seed oil decreases during seeds maturation. The result shows that mature camellia tea seed oil is mainly composed of oleic acid (C18:1) 72.33%, linoleic acid (C18:2) 13.39% and palmic acid (C16:0) 10.19%. As the result, the most appropriate harvesting time of C. tenuifolia in northern Taiwan is from mid October to November in order to get fruits with highest oil content and unsaturated fatty acid for tea seed oil production.