To understand antioxidant enzyme response of two contrasting Arundinella hirta ecotypes to drought stress, drought-tolerant Youngduk and drought-sensitive Jinju-1, were comparatively analyzed changes in the enzymatic activities of peroxidase (POD), ascorbate peroxidase (APX), catalase (CAT), superoxide dismutase (SOD), and glutathione reductase (GR). Two ecotypes, drought-tolerant Youngduk and drought-sensitive Jinju-1 were subjected to drought stress by withholding water for 12 days. ROS accumulation level and electrolytic leakage were significantly increased in both A. hirta ecotypes by drought stress treatment but less in Youngduk than Jinju-1. The RWC significantly decreased in both the drought stress-treated ecotypes as compared to control, but less in Youngduk than Jinju-1. Soluble sugar and protein content were increased more in drought stress-treated Youngduk as compared to Jinju-1. The activities of antioxidant enzymes such as SOD, CAT, POD, APX, and GR increased significantly in both the drought stress-treated ecotypes Youngduk and Jinju-1 as compared to control. The increase in antioxidant enzyme activity level was more prominent in drought stress-treated Youngduk as compared to Jinju-1. Taken together, these results suggest that Youngduk was more tolerant to drought stress than Jinju-1, and seem to indicate that tolerance of A. hirta to drought stress is associated with increased activity of antioxidant enzymes.

Ⅰ. INTRODUCTION
Ⅱ. MATERIALS AND METHODS
    1. Plant materials and growth
    2. Drought stress treatment
    3. Measurement of O2- and OH･
    4. Measurement of electrolytic leakage
    5. Measurement of relative water content (RWC), solubleprotein and soluble sugar
    6. Measurement of antioxidant enzymes activities
    7. Statistical analysis
Ⅲ. RESULTS
    1. Alterations in ROS and electrolytic leakage
    2. Alterations in RWC, soluble sugar and proteincontent
    3. Alterations in antioxidant enzymes activities
Ⅳ. DISCUSSION
Ⅴ. ACKNOWLEDGMENTS

• Chang Woo Min(Department of Animal Bioscience, Division of Applied Life Science (BK21), IALS, Gyeongsang National University, Jinju 52828, Republic of Korea)
• Yun-Hee Kim(Department of Biology Education, IALS, Gyeongsang National University, Jinju 52828, Republic of Korea)
• Byung-Hyun Lee(Department of Animal Bioscience, Division of Applied Life Science (BK21), IALS, Gyeongsang National University, Jinju 52828, Republic of Korea) Corresponding author