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This study was carried out to investigate the effects of shading on the growth, and to compare the shade tolerances of 20 Hibiscus syriacus cultivars under different shading levels of 0, 55, and 95% of incident sunlight. Shoot length of ´Asadal´, ´Hwarang´, and ´Pulkkot´ was longer under 55 or 95% shading levels than control, but that of ´Honghwarang´ and ´Nulsarang´ was shorter. The leaf number of ´Arang´, ´Honghwarang´, ´Nulsarang´, ´Pyonghwa´, and ´Shintaeyang´ decreased when light intensity was decreased. Leaves of many cultivars were longer with decreasing light intensity, but ´Honghwarang´ and ´Sanchonyo´ were shorter than control. Under 95% shading level, shoot dry weight of ´Asadal´, ´Hanoi-tanshim´, ´Hwarang´, ´Paedal´, ´Paektanshim´, ´Parangsae´, and ´Saebit´ were not significantly different when compared to those under full sunlight condition. As shading level increased, reduction rate of root dry weight in ´Asadal´, ´Paektanshim´, and ´Saebit´ were lower than that in other cultivars. ´Hanoi-tanshim´, ´Hwarang´, ´Pulkkot , ´Parangsae´, and ´Saebit were good cultivars in flowering, whereas ´Arang´, ´Hanoi´, ´Nulsarang´, ´Paedal´, and ´Sanchonyo´ did not flower at all under 95% shading level. Chlorophyll content were highly increased in ´Hanoi´, ´Hanoi-tanshirri , ´Paektanshim´, ´Parangsae´, ´Pulkkot´, ´Saeachim´, and ´Shintaeyang´ under shade condition. Among 20 Hibiscus syriacus cultivars, ´Asadal´, ´Hanoi-tanshim´, ´Paektanshim´, and ´Saebit´ can be recommended for planting in 55-95% shading area.
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