Pang Jia Yin, Newman Ian, Mendham Neville, Zhou Meixue, Shabala Sergey
School of Agricultural Science and Tasmanian Institute of Agricultural Research, University of Tasmania, Private Bag 54, Hobart, Tasmania 7001, Australia.
Plant Cell Environ. 2006 Jun;29(6):1107-21. doi: 10.1111/j.1365-3040.2005.01486.x.
Hypoxia-induced changes in net H+, K+ and O2 fluxes across the plasma membrane (PM) of epidermal root cells were measured using the non-invasive microelectrode ion flux measurement (MIFE) system in elongation, meristem and mature root zones of two barley (Hordeum vulgare L.) varieties contrasting in their waterlogging (WL) tolerance. The ultimate goal of this study was to shed light on the mechanisms underlying effects of WL on plant nutrient acquisition and mechanisms of WL tolerance in barley. Our measurements revealed that functionally different barley root zones have rather different O2 requirements, with the highest O2 influx being in the elongation zone of the root at about 1 mm from the tip. Oxygen deprivation has qualitatively different effects on the activity of PM ion transporters in mature and elongation zones. In the mature zone, hypoxic treatment caused a very sharp decline in K+ uptake in the WL sensitive variety Naso Nijo, but did not reduce K+ influx in the WL tolerant TX9425 variety. In the elongation zone, onset of hypoxia enhanced K+ uptake from roots of both cultivars. Pharmacological experiments suggested that hypoxia-induced K+ flux responses are likely to be mediated by both K(+) -inward- (KIR) and non-selective cation channels (NSCC) in the elongation zone, while in the mature zone K(+) -outward- (KOR) channels are the key contributors. Overall, our results suggest that oxygen deprivation has an immediate and substantial effect on root ion flux patterns, and that this effect is different in WL-sensitive and WL-tolerant cultivars. To what extent this difference in ion flux response to hypoxia is a factor conferring WL tolerance in barley remains to be answered in future studies.
利用非侵入式微电极离子通量测量（MIFE）系统，在两个耐涝性不同的大麦（Hordeum vulgare L.）品种的伸长区、分生区和成熟根区，测量了缺氧诱导的表皮根细胞质膜（PM）上净H⁺、K⁺和O₂通量的变化。本研究的最终目标是阐明涝害对植物养分吸收影响的潜在机制以及大麦耐涝机制。我们的测量结果表明，功能不同的大麦根区对O₂的需求差异很大，根伸长区距根尖约1 mm处的O₂内流最高。缺氧对成熟区和伸长区质膜离子转运体的活性有质的不同影响。在成熟区，缺氧处理导致涝敏感品种Naso Nijo的K⁺吸收急剧下降，但未降低涝耐受品种TX9425的K⁺内流。在伸长区，缺氧开始增强了两个品种根的K⁺吸收。药理学实验表明，缺氧诱导的K⁺通量反应可能由伸长区的K⁺内向（KIR）通道和非选择性阳离子通道（NSCC）介导，而在成熟区，K⁺外向（KOR）通道是关键因素。总体而言，我们的结果表明，缺氧对根离子通量模式有直接且显著的影响，并且这种影响在涝敏感和涝耐受品种中有所不同。这种对缺氧的离子通量反应差异在多大程度上是大麦耐涝的一个因素，仍有待未来研究解答。
