To determine whether the enhanced UV-B causes oxidative stress, and to test the relationship between plant growth response and biochemical defense response to UV-B, two soybean plants, Keunolkong, a highly UV-B susceptible cultivar, and Danyeubkong, a less UV-B susceptible cultivar, were subjected to the enhanced UV-B [daily dose : 0.06 (control) and 11.32 (enhanced UV-B) kJ m^-2 ; UV-B_BE] for 3 weeks. Contents of malondialdehyde and total carotenoid were increased in Keunolkong compared with Danyeubkong by UV-B. In control plants, ascorbate level of Danyeubkong was 3 times higher than that of Keunolkong. The ratio of dehydroascorbate/ascorbate was highly increased in Keunolkong by UV-B. The activities of antioxidative enzyme such as superoxide dismutase, ascorbate peroxidase, monodehydroascorbate reductase and glutathione reductase were increased in both cultivars by UV-B. This results indicate that enhanced UV-B caused oxidative stress in both two cultivars, especially in Keunolkong. Susceptibility of two soybean cultivars to UV-B is closely related to the levels of antioxidants such as carotenoid and ascorbate.

• 김학윤(경북대학교 농업과학기술연구소) | Hak-Yoon Kim (Institute of Agricultural Sciences and Technology, Kyungpook National University)
• 박이상(경북대학교 농학과) | Yi-Sang Park (Department of Agronomy, Kyungpook National University)
• 이인중(경북대학교 농업과학기술연구소) | In-Jung Lee (Institute of Agricultural Sciences and Technology, Kyungpook National University)
• 신동현(경북대학교 농학과) | Dong-Hyun Shin (Department of Agronomy, Kyungpook National University)
• 김길웅(경북대학교 농학과) | Kil-Ung Kim (Department of Agronomy, Kyungpook National University)