叶施NO对NaCl胁迫下红砂幼苗叶片和根系中氮代谢酶及营养物质的影响

以当年生红砂(Reaumuria soongorica)幼苗为材料，采用盆栽实验，考察叶面喷施不同浓度(0、0.01、0.10、0.25、0.50、1.00 mmol·L^-1)NO供体硝普钠 (SNP) 对NaCl(300 mmol·L^-1)胁迫下红砂根、叶中可溶性蛋白、游离氨基酸和硝态氮含量，以及谷氨酰胺合成酶(GS)、谷氨酸合酶(GOGAT)、硝酸还原酶(NR)活性的影响，并采用主成分分析和隶属函数法筛选NO对NaCl胁迫缓解效应的氮代谢指标和最佳NO浓度，以探讨外源NO对NaCl 胁迫下红砂缓解效应的氮代谢响应机制。结果表明：(1)在300 mmol·L^-1 NaCl胁迫处理下，红砂幼苗根、叶中可溶性蛋白、硝态氮含量以及GS、GOGAT、NR活性均比对照显著下降。(2)外源NO能显著提高盐胁迫下红砂叶、根中GS、GOGAT、NR活性和硝态氮含量，增加根中可溶性蛋白和游离氨基酸含量。(3)NR和GOGAT活性可用于评价NO对NaCl胁迫下红砂幼苗的缓解作用，外源NO(SNP)对红砂幼苗在NaCl胁迫下的缓解效果强弱表现为0.25 mmol·L^-1> 0.50 mmol·L^-1> 0.10 mmol·L^-1> 1.00 mmol·L^-1> 0.01 mmol·L^-1。研究发现，300 mmol·L^-1 NaCl胁迫显著抑制了红砂幼苗氮代谢，外源NO(SNP)有助于提高盐胁迫下红砂NR活性，加快硝态氮转化为铵态氮，促进红砂叶片和根中GS/GOGAT对转化物的同化，从而增强红砂幼苗的耐盐性，并以0.25 mmol·L^-1SNP处理时缓解作用最佳；NR和GOGAT活性可作为NO缓解盐胁迫的评价指标。

Effect of Foliar spraying Nitric Oxide on the Nitrogen Metabolism Enzyme Activities and Nutrients in Leaves and Roots of Reaumuria soongorica Seedlings under NaCl Stress

The objectives of this experiment were to study the effects of foliar spraying nitric oxide (NO) on N metabolism enzyme activities and nutrients of Reaumuria soongorica seedlings leaves and roots under NaCl stress and to determine the ability of exogenous NO to alleviate NaCl stress in R. soongorica seedlings. The current year R. soongorica seedlings were used as test material to measure the activities of glutamine synthetase (GS), glutamate synthetase (GOGAT) and nitrate reductase (NR), the concentrations of soluble protein, free amino acid and NO^-₃ N in roots and leaves by different concentrations of NO (0, 0.01, 0.10, 0.25, 0.50 and 1.00 mmol·L^-1 sodium nitroprusside) under 300 mmol·L^-1 NaCl stress in this pot experiment. Principal component and subordinate function analysis were used to select the best N metabolism indexes and optimal NO concentration for evaluating the ability of NO to alleviate NaCl stress in R. soongorica seedlings. The results showed that: (1) GS, GOGAT and NR activities and soluble protein and NO^-₃ N concentrations all decreased significantly under 300 mmol·L^-1 NaCl stress. (2) Exogenous NO can significantly increase GS, GOGAT and NR activities and nitrate nitrogen concentrations in R. soongorica roots and leaves, and increase soluble protein and free amino acid concentrations in roots. (3) NR and GOGAT activities can be used to evaluate the mitigation effect of NO on R. soongorica seedlings under NaCl stress and order of the mitigating effect of exogenous NO on R. soongorica seedlings under NaCl stress is 0.25 mmol·L^-1SNP > 0.50 mmol·L^-1 SNP > 0.10 mmol·L^-1SNP > 1.00 mmol·L^-1SNP > 0.01 mmol·L^-1SNP by principal component and subordinate function analysis. The study found that 300 mmol·L^-1 NaCl stress inhibited N metabolism. Exogenous NO helped R. soongorica seedlings adapt to NaCl stress by increasing NR activities and promoting NO^-₃ N transformate to NH⁺₄ and by promoting the assimilation of NH⁺₄ via the GS/GOGAT cycle in R. soongorica roots and leaves. The results showed that 0.25 mmol·L^-1SNP treatment was the most effective for alleviating NaCl stress in R. soongorica seedlings. NR and GOGAT activities can be used to evaluate the ability of NO to alleviate NaCl stress in R. soongorica.