γ–氨基丁酸对低氧胁迫下甜瓜幼苗氮代谢及矿质元素含量的影响

Effects of Exogenous γ-aminobutyric Acid on Inorganic Nitrogen Metabolism and Mineral Elements Contents of Melon Seedling Under Hypoxia Stress

以甜瓜‘西域1号’为材料,采用营养液水培方法,研究了低氧胁迫下外源γ–氨基丁酸(GABA)对幼苗根系无机氮代谢及矿质元素含量的影响。试验结果表明,低氧胁迫下甜瓜根系中硝酸还原酶(NR)、亚硝酸还原酶(NiR)活性显著提高,硝态氮(NO3--N)、亚硝态氮(NO2--N)、铵态氮(NH4+-N)以及谷氨酸、氨基酸、总氮含量显著增加,而可溶性蛋白含量显著降低,同时K+、Ca2+、Mg2+、Zn含量显著降低,Mn、Fe、Cu含量大幅提高,根系生长受到严重抑制;低氧胁迫下添加外源GABA处理的甜瓜根系中NO3--N、NO2--N、NH4+-N、谷氨酸、氨基酸、可溶性蛋白质、总氮、K+、Ca2+、Mg2+、Zn含量以及NR、NiR活性显著高于低氧胁迫处理,而Mn、Fe、Cu含量显著降低,缓解了低氧胁迫对根系生长的抑制;低氧胁迫下同时添加GABA和钨酸钠处理的根系NR活性显著降低,同时NiR活性和NO3--N、NH4+-N、谷氨酸、氨基酸、可溶性蛋白质、总氮含量和根系干质量均显著降低。说明低氧胁迫下外源GABA可以通过诱导NR活性的提高促进硝酸盐的吸收和转化,通过提高K+、Ca2+、Mg2+、Zn的吸收和减少Mn、Fe、Cu的吸收,缓解低氧胁迫甜瓜根系的伤害。

Melon‘Xiyu 1’was used to investigate the effect of exogenous γ-aminobutyric acid （GABA）on the inorganic nitrogen metabolism and mineral elements contents under hypoxia stress in hydroponics culture. The result showed that the activities of nitrate reductase（NR）,nitrite reductase（NiR） and the contents of nitrate（NO3--N）,nitrite（NO2--N）,ammonium（NH4＋-N）,glutamic acid,amino acids,total nitrogen as well as Mn,Fe,Cu significantly increased in roots of melon seedlings under hypoxia stress,however the contents of soluble protein and K＋,Ca2＋,Mg2＋,Zn obviously decreased, as a result the growth of roots was inhibited;Compared with hypoxia stress,the contents of NO3--N, NO2--N,NH4＋-N,glutamic acid,amino acids,soluble protein and activities of NR,NiR in roots were significantly increased when melon seedlings were grown in the nutrient solution of applying GABA under hypoxia stress,meanwhile the mineral elements contents in roots such as total nitrogen,K＋,Ca2＋,Mg2＋, Zn were significantly increased,but the contents of Mn,Fe,Cu were significantly decreased,which relieved the inhibition of hypoxia to roots in melon seedlings. However,exogenous GABA and sodium tungstate application aggravated the harm of hypoxia stress to melon seedlings through inhibiting NR activity and decreasing contents of NO3--N,NH4＋-N,glutamic acid,amino acids,soluble protein,total nitrogen and dry weight in roots. The result indicated that exogenous GABA might alleviate the damage of melon seedlings from hypoxia stress via enhancing NR activity and improving nitrate absorption and transformation,meanwhile increasing K＋,Ca2＋,Mg2＋,Zn contents and decreasing Mn,Fe,Cu contents in the roots.