Growth and Photosynthetic Responses of Taraxacum coreanum Nakai Seedlings according to the Shading Levels

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Taraxacum coreanum, a member of the Asteraceae family, is endemic to Korea and has high potential as a medicinal crop. However, as the cultivation method for T. coreanum has not been clearly established, it is necessary to discuss the proper method by which to raise seedlings. In this study, the effects of the shading levels on growth and photosynthetic responses of T. coreanum were investigated. The shading treatment in this study had five levels: 35, 45, 60, 75, and 99%, respectively, designed with polyethylene shade films. The plant height, plant width, leaf length, and leaf width were highest with the 75% shading level, while the root length, root fresh weight, and dry weight tended to increase as the shading level decreased. The fresh and dry weights of the shoots were highest at the 60–75% shading levels. PIABS, representing the performance index on an absorption basis, was highest at 7.13 at the 60% shading level, showing a trend similar to that of the fresh weight and dry weight of the shoots. The maximum quantum yield of PSII (Fv/Fm) was 0.83–0.84 at shading levels of 35–75%, but it decreased to 0.74 at the 99% shading level. ΦDo, ABS/RC, and DIo/RC showed equal significance levels from shading levels of 35–75% and belonged to the normal range. However, these indicators of stress were highest at the 99% shading level, indicating that setting an excessively high shading level could significantly inactivate the reaction center of PSII. In conclusion, for the cultivation of T. coreanum under different shading levels, it is recommended to utilize shading levels of 60–75% to enhance the shoot sizes and fresh and dry weights significantly. Additionally, for significant enhancements in root length and growth, it is recommended to use shading levels of 35–75%, specifically excluding the 99% shading level.