Ammonium Uptake by Rice Roots (III. Electrophysiology)
Ammonium Uptake by Rice Roots (III. Electrophysiology)
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DOI：
10.1104/pp.104.3.899
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发表时间：
1994-03
期刊：
影响因子：
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通讯作者：
Miao Yuan Wang;Anthony D. M. Glass;J. Shaff;Leon V. Kochian
中科院分区：
文献类型：
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作者：
Miao Yuan Wang;Anthony D. M. Glass;J. Shaff;Leon V. Kochian
在 2 或 100 μM NH4+ 中生长的 3 周龄水稻 (Oryza sativa L. cv M202) 幼苗 (分别为 G2 或 G100 植物) 的完整根的表皮和皮层细胞中测量跨膜电位差 (δψ)。在不含氮的改进的约翰逊营养液中，δψ在-120至-140mV的范围内。将 NH4+ 引入沐浴介质会导致快速去极化。在稳定状态下，G2和G100植物的平均δψ分别为-116和-89mV。这种去极化表现出对外部 NH4+ 浓度的双相响应，类似于报道的 13NH4+ 流入等温线 (M.Y. Wang, M.Y. Siddiqi, T.J. Ruth, A.D.M. Glass [1993] Plant Physiol 103: 1259–1267)。膜去极化与 13NH4+ 流入的图也是双相的，表明两个运输系统有不同的耦合过程，两个浓度范围之间的断点约为 1 mM NH4+。去极化程度还受到氮状态的影响，G2 植物的去极化程度大于 G100 植物。由质子载体(羧基氰化物-间氯苯腙)、ATP合成抑制剂(氰化钠加水杨异羟肟酸)或ATP酶抑制剂(己烯雌酚)消除了由于NH 4+ 吸收引起的δψ去极化。这些观察结果在跨根细胞质膜的高亲和力和低亲和力运输系统吸收 NH4+ 的机制的背景下进行了讨论。
The transmembrane electrical potential differences ([delta][psi]) were measured in epidermal and cortical cells of intact roots of 3-week-old rice (Oryza sativa L. cv M202) seedlings grown in 2 or 100 [mu]M NH4+ (G2 or G100 plants, respectively). In modified Johnson's nutrient solution containing no nitrogen, [delta][psi] was in the range of -120 to -140 mV. Introducing NH4+ to the bathing medium caused a rapid depolarization. At the steady state, average [delta][psi] of G2 and G100 plants were -116 and -89 mV, respectively. This depolarization exhibited a biphasic response to external NH4+ concentration similar to that reported for 13NH4+ influx isotherms (M.Y. Wang, M.Y. Siddiqi, T.J. Ruth, A.D.M. Glass [1993] Plant Physiol 103: 1259–1267). Plots of membrane depolarization versus 13NH4+ influx were also biphasic, indicating distinct coupling processes for the two transport systems, with a breakpoint between two concentration ranges around 1 mM NH4+. The extent of depolarization was also influenced by nitrogen status, which was larger for G2 plants than for G100 plants. Depolarization of [delta][psi] due to NH4+ uptake was eliminated by a protonophore (carboxylcyanide-m-chlorophenylhydrazone), inhibitors of ATP synthesis (sodium cyanide plus salicylhydroxamic acid), or an ATPase inhibitor (diethylstilbestrol). The results of these observations are discussed in the context of the mechanisms of NH4+ uptake by high- and low-affinity transport systems operating across the plasma membranes of root cells.