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为探讨外源NO对Na_2CO_3胁迫下南瓜幼苗碳氮代谢过程的影响,以银辉2号南瓜品种为材料,采用盆栽法研究了80μmol·L-1SNP对60 mmol·L-1Na_2CO_3胁迫下南瓜幼苗生长、叶绿体色素含量、碳氮代谢相关酶活性及代谢产物量的变化规律。结果表明:Na_2CO_3胁迫12 d,南瓜幼苗地上和地下部分干重、相对生长量、根冠比、Rubisco羧化活力、光合色素含量和氮代谢相关酶活性均不同程度下降;Rubisco氧化活力、游离氨基酸总量和蛋白水解酶活性显著上升。80μmol·L-1SNP外源处理能明显缓解Na_2CO_3胁迫对南瓜幼苗生长及光合作用的抑制,增加了干物质的积累和光合色素的含量。与Na_2CO_3胁迫处理相比,干物质积累量、相对生长量、叶绿素和类胡萝卜素(caro)含量、硝酸还原酶(NR)、谷氨酰胺合成酶(GS)、Rubisco羧化酶、淀粉酶(AMY)活性和可溶性蛋白含量分别提高了26.72%、30.45%、17.69%、46.15%、46.43%、30.70%、38.75%、70.0%、65.37%;Rubisco加氧酶、蛋白水解酶活性和游离氨基酸总量分别降低了18.29%、31.76%、28.57%。外源NO通过促进淀粉酶和Rubisco羧化活性的提高和氧化活性的下降,维持了可溶性总糖含量的稳定;通过增强NR、GS和谷氨酸合酶(GOGAT)活性、抑制蛋白水解酶和谷氨酸脱氢酶(GDH)活性,降低叶片中游离氨基酸含量,增加了蛋白质的积累。本研究结论:碱性盐胁迫下,80μmol·L-1的SNP通过增强南瓜幼苗的光合碳代谢,促进了酮酸转化为氨基酸。通过提高氮代谢相关酶NR、GS、GOGAT活性,促使碳流由光合碳代谢转向氮代谢,维持了盐害下南瓜幼苗碳氮代谢的正常进行,增强了南瓜幼苗抵御Na_2CO_3胁迫的能力。
In order to investigate the effects of exogenous NO on carbon and nitrogen metabolism of pumpkin seedlings under Na_2CO_3 stress, the effects of 80 μmol·L -1 SNP on the growth of pumpkin seedlings under 60 mmol·L -1 Na_2CO_3 stress , Chlorophyll pigment content, enzyme activities related to carbon and nitrogen metabolism, and the amount of metabolites. The results showed that on the 12th day after Na_2CO_3 stress, the dry weight, relative growth, root / shoot ratio, carboxylation activity of Rubisco, photosynthetic pigment content and activities of nitrogen metabolism related enzymes of pumpkin seedlings all decreased to different extents. Rubisco oxidation activity, free amino acids Total amount and proteolytic enzyme activity increased significantly. Exogenous treatment with 80μmol·L-1 SNP could significantly alleviate the inhibition of Na_2CO_3 stress on the growth and photosynthesis of pumpkin seedlings, increasing the accumulation of dry matter and photosynthetic pigment content. Compared with Na_2CO_3 stress treatment, the dry matter accumulation, relative growth, chlorophyll and carotenoid content, NR, GS, Rubisco carboxylase, amylase AMY activity and soluble protein content increased by 26.72%, 30.45%, 17.69%, 46.15%, 46.43%, 30.70%, 38.75%, 70.0%, 65.37%, respectively. The activities of Rubisco oxygenase, proteolytic enzyme and free amino acids Respectively, decreased by 18.29%, 31.76%, 28.57%. Exogenous NO can maintain the stability of total soluble sugar content by promoting the increase of carboxylase activity and decrease of oxidation activity of amylase and Rubisco. By increasing the activity of NR, GS and GOGAT, the activity of protease and Glutamate dehydrogenase (GDH) activity, reduce free amino acid content in leaves, increased protein accumulation. The results showed that under alkaline salt stress, 80μmol·L-1 SNP promoted the conversion of ketoacid to amino acids by enhancing photosynthetic carbon metabolism of pumpkin seedlings. By increasing the activities of nitrogen, nitrogen and metabolism related enzymes NR, GS and GOGAT, the carbon flux was shifted from photosynthetic carbon metabolism to nitrogen metabolism, and the nitrogen and carbon metabolism of pumpkin seedlings was maintained under the salt stress, which enhanced the ability of pumpkin seedlings to resist Na_2CO_3 stress.