Electrophysiological responses of maize roots to low water potentials: relationship to growth and ABA accumulation
Electrophysiological responses of maize roots to low water potentials: relationship to growth and ABA accumulation
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DOI：
10.1093/jxb/erg060
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发表时间：
2003-02-01
影响因子：
6.9
通讯作者：
Sharp, RE
中科院分区：
文献类型：
--
作者：
Ober, ES;Sharp, RE
根伸长的维持是对低水势（psi（w））的重要适应性反应，但对其调节知之甚少。一个重要组成部分可能是根细胞电生理学的变化，它既发出信号又维持生长维持过程。作为该假设的第一次检验，在玉米 (Zea mays L.) 主根的细胞伸长区内测量了膜电位 (E(m))。幼苗在含氧溶液培养物中生长，并通过逐渐添加聚乙二醇来施加低psi(w)。细胞响应低 psi(w) 超极化约 25 mV，48 小时后，与高 psi(w) 下的根相比，在低于 -0.3 MPa 的 psi(w) 下静息电位仍显着超极化。抑制剂实验表明超极化依赖于质膜H(+)-ATP酶活性。先前的工作表明，在低 psi(w) 下，需要积累脱落酸 (ABA) 来维持玉米初生根的伸长。为了确定 ABA 的作用机制是否涉及根部电生理学的变化，在长期暴露于低 psi(w) 的情况下进行了 Em 测量。在细胞伸长的维持依赖于 ABA 积累的区域（距离顶点 2-3 毫米），或者无论 ABA 状态如何都抑制伸长的区域（距离顶点 6-8 毫米），测量稳态静息 Em。在 ABA 缺陷的根中，特别是在 2-3 毫米区域，Em 的负值要大得多。结果表明，离子稳态设定点的变化与低 psi(w) 下根细胞伸长的维持有关，ABA 积累在调节参与该反应的离子转运过程中发挥着作用。
The maintenance of root elongation is an important adaptive response to low water potentials (psi(w)), but little is known about its regulation. An important component may be changes in root cell electrophysiology, which both signal and maintain growth maintenance processes. As a first test of this hypothesis, membrane potentials (E(m)) were measured within the cell elongation zone of maize (Zea mays L.) primary roots. Seedlings were grown in oxygenated solution culture, and low psi(w) was imposed by the gradual addition of polyethylene glycol. Cells hyperpolarized approximately 25 mV in response to low psi(w), and after 48 h resting potentials remained significantly hyperpolarized at psi(w) lower than -0.3 MPa compared with roots at high psi(w). Inhibitor experiments showed that the hyperpolarization was dependent on plasma membrane H(+)-ATPase activity. Previous work showed that accumulation of abscisic acid (ABA) is required for the maintenance of maize primary root elongation at low psi(w). To determine if the mechanism of action of ABA involves changes in root electrophysiology, Em measurements were made during long-term exposure to low psi(w). Steady-state resting Em were measured in regions in which maintenance of cell elongation was dependent on ABA accumulation (2-3 mm from the apex), or in which elongation was inhibited regardless of ABA status (6-8 mm from the apex). Em was substantially more negative in ABA-deficient roots specifically in the 2-3 mm region. The results suggest that set-points for ion homeostasis shifted in association with the maintenance of root cell elongation at low psi(w), and that ABA accumulation plays a role in regulating the ion transport processes involved in this response.