本試驗調查外施亞硝基鐵氰化鈉(一氧化氮提供者)於改善長期受淹水逆境的甜瓜幼 苗之角色。7天的長期淹水會顯著地減少甜瓜幼苗的枝梢及根的生物量，而補充50 — 氧化氮會增進淹水逆境下甜瓜幼苗的枝梢以及根的重量與長度。長期淹水逆境也會增加甜 瓜幼苗細胞的活性氧分子含量及脂質過氧化程度。處理一氧化氮可使淹水造成活性氧分子 降至基本量並增加滲透物質，施用一氧化氮亦會增加抗氧化酵素活性。因此，本研究建議 外施一氧化氮會明顯地增進甜瓜幼苗之淹水耐受性，藉由增加植株的抗氧化防禦系統及滲 透調節能力以減緩膜傷害。

We investigated the role of exogenously applied sodium nitroprusside, a NO donor, in ameliorating long term waterlogging stress on melon seedlings. Long term waterlogging stress over 7 day period drastically affected the plants as indicated by decreased biomass of shoots and roots of melon seedlings. In contrast, supplementation with 50 f.!M NO improved growth of melon seedlings under waterlogging and it was proved by increased shoots and root weights and root lengths. Further analysis showed that long-term waterlogging stress led to increased cellular reactive oxygen species (ROS) content and high levels of lipid peroxidation in the melon seedlings. Treatments with NO and flooding stress resulted in reversal of ROS to basal levels and increasing osmolytes. This study showed that application of NO resulted in increased antioxidant enzymatic activity. Hence, we propose that exogenously applied NO considerably improved waterlogging tolerance of melon seedlings by upgrading the plant antioxidative defense system level and the capacity for osmotic adjustment to alleviate membrane damage.