This paper investigated the effects of exogenous y-aminobutyric acid (GABA) on reactive oxygen species (ROS) metabolism of melon seedlings 'Xiyu 1' under normoxia and hypoxia stress with hydroponics culture. Seedlings were cultured under normoxia +GABA (5 mmol · L-1), hypoxia stress, hypoxia stress+GABA (5 mmol · L-1) respectively for 0,2,4,6,8 d,and with normoxia treatment as the control. The results showed that the productive rate of O2,contents of H2O2 and MDA in roots and leaves were significantly increased when melon seedlings were grown in the nutrient solution under hypoxia stress. Meanwhile,the activities of SOD,POD,CAT, APX,GR and the contents of AsA,GSH were increased compared with control. Exogenous GABA application under hypoxia stress could significantly decreased the productive rate of O2-1 ,the contents of H2O2 and MDA of melon seedlings by increasing the activities of SOD,CAT, APX, GR and the contents of AsA,GSH. However, exogenous GABA application had less effect on ROS metabolism under normoxia condition, including significantly improved the activities of CAT,GR and the contents of AsA,GSH,significantly decreased the contents of H2O2 and MDA,but hadlittle influence on other physiological indexes. The results suggested that exogenous GABA alleviated the harm of hypoxia stress in melon,most likely by decreasing ROS accumulation and maintaining the stability of cell membrane structure through significantly increasing antioxidant enzyme activities and antioxidant substance contents in roots and leaves of melon seedlings.%以甜瓜品种‘西域一号’幼苗为材料,采用营养液水培方法,设置正常通气(对照)、正常通气+ GABA(5mmol·L-1)、低氧胁迫、低氧胁迫+GABA(5 mmol·L-1)4个处理,研究了外源γ-氨基丁酸(GABA)对正常通气和低氧胁迫下甜瓜幼苗活性氧代谢的影响.结果表明:与正常通气处理相比,低氧胁迫处理导致甜瓜幼苗体内O-·2产生速率和H2O2、MDA含量显著增加,同时SOD、POD、CAT、APX、GR等抗氧化酶活性和抗氧化物质AsA、GSH含量显著提高.低氧胁迫下外源GABA能显著提高甜瓜幼苗叶片SOD、CAT、APX、GR等酶活性和AsA、GSH含量,降低了植株体内O-·2产生速率和H2O2、MDA含量；而正常通气条件下添加外源GABA处理对甜瓜幼苗活性氧代谢的影响较小,仅CAT、GR活性和AsA、GSH含量显著提高,而H2O2、MDA含量显著降低.结果证明,添加外源GABA可以通过显著提高低氧胁迫下抗氧化酶活性和抗氧化物质含量来降低甜瓜幼苗活性氧积累,维持其细胞膜结构稳定性,从而有效减轻低氧胁迫对甜瓜幼苗的伤害.
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