Nitrate uptake and nitrite release by tomato roots in response to anoxia
Nitrate uptake and nitrite release by tomato roots in response to anoxia
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DOI：
10.1016/j.jplph.2003.11.003
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发表时间：
2004-07-01
影响因子：
4.3
通讯作者：
Lamaze, T
中科院分区：
文献类型：
--
作者：
Morard, P;Silvestre, J;Lamaze, T
通过放置水培根基质7，停止通风，使番茄植株的离体根系统(结果早期、第2次冲洗)从常氧逐渐过渡到缺氧。培养液中氧含量和呼吸速率在处理12h后下降，达到极低值，表明此后组织处于缺氧状态。缺氧(26h后)强烈刺激了营养液中硝酸盐的流失，亚硝酸盐仅在处理16h后开始释放。这种影响在无根或有钨酸盐存在的情况下观察不到，但在全株或无菌的体外培养的根组织中发生。这些结果表明，根中的生化过程涉及硝酸还原酶。番茄根中硝酸还原酶活性在缺氧过程中呈上升趋势。这一现象出现在完整植株和去顶植株的根组织中。缺氧对硝酸盐吸收的刺激作用是特定的；缺氧同时导致根释放正磷酸盐、硫酸盐和钾。缺氧促进了根组织对硝酸盐的还原，亚硝酸根离子被释放到木质部汁液和培养基中。就总体余额而言，回收的亚硝酸盐只占利用的硝酸盐数量的一半。亚硝酸盐还原为一氧化氮，可能还会转化为氮气，这可能是造成这种差异的原因。这些结果似乎是首次报道了番茄结实早期在缺氧条件下植物根系对硝酸盐的吸收增加，而窒息的根系在营养介质中释放亚硝酸盐的速度是迄今报道的最快的。(C)2004年爱思唯尔股份有限公司。版权所有。
Excised root systems of tomato plants (early fruiting stage, 2nd flush) were subjected, to a gradual transition from normoxia to anoxia by seating the hydroponic root medium 7 while aeration was stopped. Oxygen level in the medium and respiration rate decreased and reached very low values after 12 h of treatment, indicating that the tissues were anoxic thereafter. Nitrate loss from the nutrient solution was strongly stimulated by anoxia (after 26 h) concomitantly with a release of nitrite starting only after 16 h of treatment. This effect was not observed in the absence of roots or in the presence of tungstate, but occurred with whole plants or with sterile in vitro cultured root tissues. These results indicate that biochemical processes in the root involve nitrate reductase. NR activity assayed in tomato roots increased during anoxia. This phenomenon appeared in intact plants and in root tissues of detopped plants. The stimulating effect of oxygen deprivation on nitrate uptake was specific; anoxia simultaneously entailed a release of orthophosphate, sulfate, and potassium by the roots. Anoxia enhanced nitrate reduction by root tissues, and nitrite ions were released into xylem sap and into medium culture. In terms of the overall balance, the amount of nitrite recovered represented only half of the amount of nitrate utilized. Nitrite reduction into nitric oxide and perhaps into nitrogen gas could account for this discrepancy. These results appear to be the first report of an increase in nitrate uptake by plant roots under anoxia of tomato at the early fruiting stage, and the rates of nitrite release in nutrient medium by the asphyxiated roots are the fastest yet reported. (C) 2004 Elsevier GmbH. All rights reserved.