[目的]本文的目的是研究外源24-表油菜素内酯(EBR)对低氧胁迫植株氮代谢的影响。[方法]以低氧耐性较弱的‘中农6号’黄瓜品种为材料,采用营养液通N2形成低氧逆境的方法,深入探讨了EBR对低氧胁迫下植株叶片和根系中与氮代谢相关的酶活性的影响。[结果]低氧处理显著降低了植株叶片的总氮含量,EBR使胁迫植株叶片总氮积累恢复至对照水平。低氧处理后,硝态氮含量在叶片中增加而在根系中降低,铵态氮的变化趋势与硝态氮相反,而EBR显著促进了胁迫植株根系的铵态氮积累。低氧胁迫下,植株根系硝酸还原酶(NR)和谷氨酰胺合成酶(GS)活性升高,随后恢复至对照水平,而谷氨酸合成酶(GOGAT)活性显著低于对照。叶片NR活性受到低氧抑制,亚硝酸还原酶(NiR)、GOGAT、氧化型谷氨酸脱氢酶(NAD+-GDH)活性则先升高,随后降低;叶片还原型谷氨酸脱氢酶(NADH-GDH)活性也受到低氧促进,至处理末期时显著高于对照植株。EBR显著提高了胁迫植株根系的NR活性及叶片的NiR、NAD+-GDH活性。[结论]黄瓜植株通过增强硝酸还原,加强氮代谢缓解低氧胁迫伤害;EBR通过增强根系NR活性及叶片NAD+-GDH活性,提高了植株的低氧耐性。[Objectives]This paper was to investigate the effect of exogenous 24-epibrassinolide on nitrogen metabolism of cucumber seedlings under hypoxia stress. [Methods]A hypoxia-sensitive cucumber genotype(Cucumis sativus‘Zhongnong 6’)was used and we investigated the effect of EBR on activity of key enzymes involved in nitrogen assimilation of plants under hypoxia. [Results]Total N content of leaves was decreased remarkably under hypoxia while EBR restored it to the control level. NO-3 content was increased in leaf but reduced in root. The change of NH+4 content was contrary to that of NO-3. EBR improved NH+4 accumulation in root under hypoxia stress. The activity of root nitrate reductase(NR)and glutamine synthetase(GS)was increased at the beginning of the stress,but recovered to that of the control level after 9 d hypoxia. While glutamate synthase(GOGAT)activity was reduced significantly at the end of the stress. Under hypoxia,activity of leaf NR was inhibited greatly,while nitrite reductase(NiR),GOGAT and oxidized glutamate dehydrogenase(NAD+-GDH)activity showed a trend of increasing-decreasing with the prolongation of the stress. After 9 d hypoxia stress,activity of leaf reduced glutamate dehydrogenase(NADH-GDH)was raised significantly. EBR greatly improved activity of root NR,leaf NiR and NAD+-GDH of the plants under hypoxia. [Conclusions]The cucumber plants acclimated to hypoxia by improving nitrate reduction and nitrogen metabolism. EBR protected the plants from oxygen limitation by accelerating activity of root NR and leaf NAD+-GDH
References
[1]
Vidal E A,Moyano T C,Canales J,et al. Nitrogen control of developmental phase transitions in Arabidopsis thaliana[J]. Journal of Experimental Botany,2014,65(19):5611-5618
[2]
Wang M,Shen Q R,Xu G H,et al. New insight into the strategy for nitrogen metabolism in plant cells[J]. International Review of Cell and Molecular Biology,2014,310:1-37
[3]
Drew M C. Oxygen deficiency and root metabolism:injury and acclimation under hypoxia and anoxia[J]. Annual Review of Plant Physiology and Plant Molecular Biology,1997,48:223-250
[4]
汪晓云. 新型无土栽培模式系列谈:(一)无土栽培技术的现状及存在问题[J]. 农业工程技术:温室园艺,2013(1):50-54 [Wang X Y. New models of soilless culture:current situation and limitation[J]. Agriculture Engineering Technology:Greenhouse and Horticulture,2013(1):50-54(in Chinese)]
[5]
郭世荣. 无土栽培学[M]. 北京:中国农业出版社,2011 [Guo S R. Soilless Culture[M]. Beijing:China Agriculture Press,2011(in Chinese)]
[6]
Geigenberger P. Response of plant metabolism to too little oxygen[J]. Current Opinion in Plant Biology,2003,6(3):247-256
[7]
Limami A M,Diab H,Lothier J. Nitrogen metabolism in plants under low oxygen stress[J]. Planta,2014,239(3):531-541
[8]
Shingaki-Wells R N,Huang S,Taylor N L,et al. Differential molecular responses of rice and wheat coleoptiles to anoxia reveal novel metabolic adaptations in amino acid metabolism for tissue tolerance[J]. Plant Physiology,2011,156(4):1706-1724
[9]
Bajguz A,Hayat S. Effects of brassinosteroids on the plant responses to environmental stresses[J]. Plant Physiology and Biochemistry,2009,47(1):1-8
[10]
Yuan L Y,Yuan Y H,Du J,et al. Effects of 24-epibrassinolide on nitrogen metabolism in cucumber seedlings under Ca(NO3)2 stress[J]. Plant Physiology and Biochemistry,2012,61:29-35
[11]
中国科学院上海植物生理研究所,上海市植物生理学会. 现代植物生理学实验指南[M]. 北京:科学出版社,1999 [Shanghai Institute of Plant Physiology,Chinese Academy of Sciences,Shanghai Society of Plant Physiology. Guide for Experimental Techniques of Plant Physiology[M]. Beijing:Science Press,1999(in Chinese)]
[12]
Glaab J,Kaiser W M. Increased nitrate reductase activity in leaf tissue after application of the fungicide Kresoxim-methyl[J]. Planta,1999,207(3):442-448
[13]
Lin C C,Kao C H. Disturbed ammonium assimilation is associated with growth inhibition of roots in rice seedlings caused by NaCl[J]. Plant Growth Regulation,1996,18(3):233-238
[14]
邱旭华. 水稻氮代谢基础研究:谷氨酸脱氢酶作用的分子机理[D]. 武汉:华中农业大学,2009 [Qiu X H. Molecular mechanism of glutamine dehydrogenase genes for primary study of the rice nitrogen metabolite[D]. Wuhan:Huazhong Agricultural University,2009(in Chinese with English abstract)]
[15]
Bradford M M. A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding[J]. Analytical Biochemistry,1976,72:248-254
[16]
Igamberdiev A U,Hill R D. Nitrate,NO and haemoglobin in plant adaptation to hypoxia:an alternative to classic fermentation pathways[J]. Journal of Experimental Botany,2004,55(408):2473-2482
[17]
Botrel A,Magne C,Kaiser W M. Nitrate reduction,nitrite reduction and ammonium assimilation in barley roots in response to anoxia[J]. Plant Physiology and Biochemistry,1996,34(5):645-652
[18]
Allègre A,Silvestre J,Morard P,et al. Nitrate reductase regulation in tomato roots by exogenous nitrate:a possible role in tolerance to long-term root anoxia[J]. Journal of Experimental Botany,2004,55(408):2625-2634
[19]
Sairam R K,Dharmar K,Chinnusamy V,et al. The role of non-symbiotic haemoglobin and nitric oxide homeostasis in waterlogging tolerance in Vigna species[J]. Biologia Plantarum,2012,56(3):528-536
[20]
Stoimenova M,Hansch R,Mendel R,et al. The role of nitrate reduction in the anoxic metabolism of roots.Ⅰ. Characterization of root morphology and normoxic metabolism of wild type tobacco and a transformant lacking root nitrate reductase[J]. Plant and Soil,2003,253(1):145-153
[21]
Horchani F,Aschi-Smiti S,Brouquisse R. Involvement of nitrate reduction in the tolerance of tomato(Solanum lycopersicum L.)plants to prolonged root hypoxia[J]. Acta Physiologiae Plantarum,2010,32(6):1113-1123
[22]
Kaiser W M,Weiner H,Huber S C. Nitrate reductase in higher plants:a case study for transduction of environmental stimuli into control of catalytic activity[J]. Physiologia Plantarum,1999,105(2):385-390
[23]
Gao H B,Jia Y X,Guo S R,et al. Exogenous calcium affects nitrogen metabolism in root-zone hypoxia-stressed muskmelon roots and enhances short-term hypoxia tolerance[J]. Journal of Plant Physiology,2011,168(11):1217-1225
[24]
Miflin B J,Habash D Z. The role of glutamine synthetase and glutamate dehydrogenase in nitrogen assimilation and possibilities for improvement in the nitrogen utilization of crops[J]. Journal of Experimental Botany,2002,53(370):979-987
[25]
Athwal G S,Pearson J,Laurie S. Regulation of glutamate dehydrogenase activity by manipulation of nucleotide supply in Daucus carota suspension cultures[J]. Physiologia Plantarum,1997,101(3):503-509
[26]
Fariduddin Q,Yusuf M,Ahmad I,et al. Brassinosteroids and their role in response of plants to abiotic stresses[J]. Biologia Plantarum,2014,58(1):9-17
