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以盐敏感型甜瓜品种‘一品天下208’为试材用80mmol·L~(-1)Ca(NO_3)_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(NO_3)_2胁迫下甜瓜幼苗硝态氮(NO_3~--N)同化的影响.结果表明:Ca(NO_3)_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(NH_4~+-N)和游离氨基酸含量增加,NO_3~--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(NO_3)_2胁迫下,外源喷施GABA有效促进了甜瓜根系对NO_3~--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NH_4~+的同化力;通过抑制GDH脱氨作用减少了甜瓜幼苗体内NH_4~+的释放量,从而缓解了盐诱导产生的NH_4~+-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NO_3~--N的同化能力,调控氨基酸代谢,进而有效缓解Ca(NO_3)_2胁迫对甜瓜幼苗的盐伤害作用.
Salt-sensitive melon cultivar ’Yipintianxia 208’ was used as experimental material. Soil salinization of 80mmol·L -1 Ca (NO_3) _2 simulating facility was carried out by deep liquid culture. The effects of exogenous γ-aminobutyric acid (GABA) ) On the assimilation of nitrate nitrogen (NO_3 - N) in melon seedlings under Ca (NO_3) _2 stress was studied.The results showed that the nitrate reductase (NR), glutamine (GS) and glutamate synthase (GOGAT) activity, and enhanced glutamate dehydrogenase (GDH), aspartate aminotransferase (GOT) and alanine aminotransferase (GPT) -N) and free amino acids, while the content of NO_3 ~ - N and soluble protein decreased, and plant growth and photosynthesis were severely inhibited.Exogenous GABA treatment effectively stimulated NO_3 ~ - N uptake and translocation into aerial parts of the muskmelon seedling and enhance the assimilation of NH4 + by the activity of NR, GS and GOGAT. The NH4 + release from muskmelon seedlings was inhibited by the inhibition of GDH deamination , Thus alleviating the ammonia poisoning caused by NH 4 + -N accumulated by salt induction. Exogenous GABA can also regulate the amino acid metabolism in melon tissues , Promote protein synthesis suggesting that exogenous GABA could enhance the assimilation of melon seedlings NO_3 ~ --N, and amino acid metabolism regulation, leading to decreased Ca (NO_3) _2 harmful effects of salt stress on melon seedlings.