Dynamic and Steady-State Responses of Inorganic Nitrogen Pools and NH3 Exchange in Leaves of Lolium perenne and Bromus erectus to Changes in Root Nitrogen Supply1
Dynamic and Steady-State Responses of Inorganic Nitrogen Pools and NH3 Exchange in Leaves of Lolium perenne and Bromus erectus to Changes in Root Nitrogen Supply1
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DOI：
10.1104/pp.010602
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发表时间：
2002-02
期刊：
影响因子：
7.4
通讯作者：
M. Mattsson;J. Schjoerring
中科院分区：
文献类型：
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作者：
M. Mattsson;J. Schjoerring
研究了两种禾本科植物（分别是富氮和贫氮草原生态系统的特征）的 11 周龄植物的无机氮库和植物-大气 NH3 交换对外部氮供应变化的短期和长期响应。将根氮源从 NO3 - 转换为 NH4 + 会在 3 小时内导致两个物种的叶质外体 NH4 + 浓度增加 3 至 6 倍，同时质外体 pH 值降低约 0.4 个 pH 单位。切换后3小时内，总可提取叶组织NH4 + 浓度也增加了两到三倍。去除外源NH4+后，质外体NH4+浓度在24 h内下降回原来水平，而叶组织NH4+浓度下降较慢，48 h后仍未达到原来水平。在稳定状态供应 NO3 - 或 NH4 + 的情况下生长 5 周后，在所有情况下，多年生黑麦草都比直立黑麦草更大，含有更多的氮，并且更有效地利用吸收的氮进行生长，而这两个物种在 NO3 - 、NH4 + 和总氮的组织浓度方面表现相反。植物。质外体 NH4+、组织 NH4+ 和 NH3 排放的稳态水平显着相关。结论表明，叶片质外体NH4+是一个高度动态的库，密切反映外部氮供应的变化。这种快速反应可能构成协调叶片氮代谢与根部实际氮吸收和外部氮可用性的信号系统。
Short- and long-term responses of inorganic N pools and plant-atmosphere NH3 exchange to changes in external N supply were investigated in 11-week-old plants of two grass species,Lolium perenne and Bromus erectus, characteristic of N-rich and N-poor grassland ecosystems, respectively. A switch of root N source from NO3 − to NH4 + caused within 3 h a 3- to 6-fold increase in leaf apoplastic NH4 + concentration and a simultaneous decrease in apoplastic pH of about 0.4 pH units in both species. The concentration of total extractable leaf tissue NH4 + also increased two to three times within 3 h after the switch. Removal of exogenous NH4 + caused the apoplastic NH4 + concentration to decline back to the original level within 24 h, whereas the leaf tissue NH4 +concentration decreased more slowly and did not reach the original level in 48 h. After growing for 5 weeks with a steady-state supply of NO3 − or NH4 +, L. perenne were in all cases larger, contained more N, and utilized the absorbed N more efficiently for growth than B. erectus, whereas the two species behaved oppositely with respect to tissue concentrations of NO3 −, NH4 +, and total N. Ammonia compensation points were higher for B. erectus than for L. perenne and were in both species higher for NH4 +- than for NO3 −-grown plants. Steady-state levels of apoplastic NH4 +, tissue NH4 +, and NH3 emission were significantly correlated. It is concluded that leaf apoplastic NH4 + is a highly dynamic pool, closely reflecting changes in the external N supply. This rapid response may constitute a signaling system coordinating leaf N metabolism with the actual N uptake by the roots and the external N availability.