국내육성 차나무 품종의 신초에서 차광이 신초의 생육과 성분 특성에 미치는 영향
Effects of Shading on Shoot Growth and Component Characteristics in Korean Tea (Carmellia sinensis L.) Cultivars
This study was designed to obtain basic data for developing production techniques of green tea powder with high quality from shading cultivation for tea varieties developed in Korea. Shading was treated by covering the shoots of three Korean tea cultivars with a 75% or 95% shading net for 15 days before plucking in each tea season. Each black polyethylene shading net was installed to produce an air space of 30 cm in height above the canopy using a supporting pole. The illuminance transmission rate was measured at 10:00 a.m. in the 3 rd tea season covering with an illuminance meter (KONICA MINOLTA T-10A, Japan) at the canopy surface composing the plucking area. Shoot growth under the natural condition for control and shoot yield and the component characteristics from shading treatments were analyzed. The shoot height was 10.9 cm, ‘Chamnok’ > 9.2 cm, ‘Keumsull’ > 7.1 cm, and ‘Beachwisull’. The leaf length was longest in ‘Chamnok’ at 9.5 cm, followed by ‘Beachwisull’ at 8.7 cm and ‘Keumsull’ at 6.5 cm. The leaf width had a similar tendency to that of the leaf length, whereas the leaf thickness was greatest in ‘Beachwisull’ at 0.31 mm, followed by ‘Chamnok’ at 0.27 mm and ‘Keumsull’ at 0.25 mm. The number of shoots per 1㎡ was 2,114 for ‘Keumsull’, 1,797 for ‘Chamnok’, and 1,592 for ‘Beachwisull’. The shoot yield from shading was much higher for ‘Chamnok’ than ‘Keumsull’ and ‘Beachwisull’. In terms of the component characteristics, covering with 95% and 75% shading nets had a tendency to increase the content of amino acids, theanine, and caffeine, but a reverse tendency in the content of cathechins, vitamin C, and tannin was observed. The crude fiber content was lower in the 1 st and 2 nd tea season, but higher in the 3 rd tea season as the shading rate was increased. The chroma a value, indicating the degree of greenness, tended to decrease significantly as the degree of shading was increased. In a comparison of cultivars, ‘Beachwisull’ was higher in amino acids, theanine, catechin, and caffeine, whereas the levels of vitamin C and crude fiber were higher in ‘Keumsull’. Chroma a was higher for ‘Keumsull’ < ‘Beachwisull’ < ‘Chamnok’ in order during all tea seasons, which indicated a higher degree of greenness in ‘Beachwisull’ and ‘Keumsull’ compared to ‘Chamnok’.
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