국화 'ARTI-purple'과 'ARTI-queen' 두 품종의 발근된 어린 식물체를 감마파이토트론을 이용하여 4주간에 걸쳐 30, 50, 70, 100Gy로 장기간 완조사를 수행하고 감마선 완조사에 따른 생육, 항산화 효소(ascorbate peroxidase, APX; catalase, CAT; peroxidase, POD; superoxidase dismutase, SOD)의 반응 및 malondialdehyde(MDA) 함량의 변화를 조사하였다. 식물의 생육은 초장, 잎의 수, 절간장, 줄기 직경, 잎 두께 등 5개 요소를 4주간의 완조사 후 관찰하였고, 식물체 초장(p<0.001), 잎의 수(p<0.001), 절간장(p<0.01), 줄기 직경(p<0.05)에서 감마선 완조사에 따른 유의적인 감소가 확인되었다. 그리고 그 가운데 절간장은 약 65Gy에서 $RD_{50}$(Reduction Dose 50)을 보이며 가장 높은 감소를 보였다. 4주 회복 기간이 지난 시점에서 항산화 반응을 확인한 결과, APX(p<0.01), SOD(p<0.01), POD(p<0.001)의 활성이 유의적인 증가를 보였고, MDA 함량은 70과 100Gy 조사구에서 유의적인 증가를 보여 산화스트레스가 상당기간 지속됨을 확인할 수 있었다. 본 연구에서 $RD_{50}$의 생육저하를 보이지 않으며, 항산화 효소의 반응 및 MDA 함량이 대조식물과 유의적이 차이를 보이지 않는 최대 선량은 50Gy이었고, 100Gy 수준에서 $RD_{50}$ 이하의 생육을 보이는 것을 확인할 수 있었다. Two chrysanthemum varieties, 'ARTI-purple' and 'ARTI-queen', were chronically irradiated with doses of 30, 50, 70, and 100 Gy for four weeks in gamma-phytotron, a long term irradiation facility. We investigated the growth, responses of antioxidant enzymes (ascorbate peroxidase, APX; catalase, CAT; peroxidase, POD; superoxidase dismutase, SOD) and malondialdehyde (MDA) contents under different doses of chronic-irradiation. The five plant growth measurements including plant height, number of leaves, internode length, stalk diameter and leaf thickness were investigated immediately after four week irradiation. The plant height (p<0.001), internode length (p<0.01), the number of leaves (p<0.001) and stalk diameter (p<0.05) were significantly decreased an increasing doses of gamma-ray. Among them, especially, the internode length was remarkably decreased showing the RD50 (Reduction Dose 50) at approximately 65 Gy. The antioxidant response after four weeks of recovery period, ascorbate peroxidase (APX) (p<0.01), superoxide dismutase (SOD) (p<0.01) and peroxidase (POD) (p<0.001) were significantly increased with an increasing dose of gamma-ray. And malondialdehyde (MDA) (p<0.01) contents showed the significant increase at the 70 and 100 Gy which means the oxidative stress was lasting for a considerable period. In this study, the 50 Gy irradiation as optimal dose showed higher growth than the $RD_{50}$, it also showed insignificant differences on the antioxidant responses and MDA contents. However, the 100 Gy dose showed lower growth than $RD_{50}$.
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