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  • Title: [Effect of exogenous γ-aminobutyric acid on NO3--N assimilation in muskmelon under Ca(NO3)2 stress].
    Author: Zhen A, Hu XH, Ren WQ, Su CJ, Jin XQ, Sun XP.
    Journal: Ying Yong Sheng Tai Xue Bao; 2016 Dec; 27(12):3987-3995. PubMed ID: 29704359.
    Abstract:
    The effect of exogenous γ-aminobutyric acid (GABA) on NO3--N assimilation in muskmelon under Ca(NO3)2 stress was investigated in ' Yipintianxia 208', a salt-sensitive melon variety cultured under deep flow hydroponics which simulated soil salinization. The results showed that under Ca(NO3)2 stress, the activities of nitrate reductase (NR), glutamate synthetase (GS) and glutamate amino transferase (GOGAT) in muskmelon seedlings were significantly reduced, while the activities of glutamate dehydrogenase (GDH), glutamate oxaloacetate transaminase (GOT) and glutamate pyruvate aminotransferase (GPT) were enhanced, leading to increased contents of NH4+-N and total amino acids, and decreased contents NO3--N and soluble protein in muskmelon, which further severely inhibited plant growth and photosynthesis of muskmelon seedlings. Exogenous GABA effectively improved the absorption of NO3--N in muskmelon roots and its transportation from root to shoot under Ca(NO3)2 stress, and improved NH4+-N assimilation by enhancing NR, GS and GOGAT activities in muskmelon seedlings. Exogenous GABA also reduced NH4+ release by limiting GDH deamination, thus further alleviated the toxication of NH4+-N induced by Ca(NO3)2 stress. In addition, foliage spraying of GABA could regulate amino acids metabolic pathways and promote protein synthesis. The results suggested that exogenous GABA could improve NO3--N assimilation and regulate amino acids metabolism to alleviate Ca(NO3)2 stress damage in muskmelon seedlings. 以盐敏感型甜瓜品种‘一品天下208’为试材,用80 mmol·L-1 Ca(NO3)2模拟设施土壤盐渍化,采用深液流水培,研究外源 γ-氨基丁酸(GABA)对Ca(NO3)2胁迫下甜瓜幼苗硝态氮(NO3--N)同化的影响.结果表明: Ca(NO3)2胁迫显著降低了甜瓜幼苗体内硝酸还原酶(NR)、谷氨酰胺合酶(GS)和谷氨酸合酶(GOGAT)活性,增强了谷氨酸脱氢酶(GDH)、谷草转氨酶(GOT)和谷丙转氨酶(GPT)活性,导致铵态氮(NH4+-N)和游离氨基酸含量增加,NO3--N和可溶性蛋白质含量下降,植株生长和光合作用受到严重抑制.Ca(NO3)2胁迫下,外源喷施GABA有效促进了甜瓜根系对NO3--N的吸收及其向地上部的转运,并通过增强NR、GS和GOGAT活性提高了甜瓜幼苗对NH4+的同化力;通过抑制GDH脱氨作用减少了甜瓜幼苗体内NH4+的释放量,从而缓解了盐诱导产生的NH4+-N积累所造成的氨毒害作用;外源喷施GABA也能调节甜瓜组织中氨基酸代谢途径,促进蛋白质的合成.表明外源GABA能增强甜瓜幼苗对NO3--N的同化能力,调控氨基酸代谢,进而有效缓解Ca(NO3)2胁迫对甜瓜幼苗的盐伤害作用.
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