School of Agricultural Science, University of Tasmania, Private Bag 54, Hobart, Tas 7001, Australia.
J Exp Bot. 2011 Jan;62(1):185-93. doi: 10.1093/jxb/erq257. Epub 2010 Aug 22.
Ionic and osmotic relations in quinoa (Chenopodium quinoa Willd.) were studied by exposing plants to six salinity levels (0-500 mM NaCl range) for 70 d. Salt stress was administered either by pre-mixing of the calculated amount of NaCl with the potting mix before seeds were planted or by the gradual increase of NaCl levels in the irrigation water. For both methods, the optimal plant growth and biomass was achieved between 100 mM and 200 mM NaCl, suggesting that quinoa possess a very efficient system to adjust osmotically for abrupt increases in NaCl stress. Up to 95% of osmotic adjustment in old leaves and between 80% and 85% of osmotic adjustment in young leaves was achieved by means of accumulation of inorganic ions (Na(+), K(+), and Cl(-)) at these NaCl levels, whilst the contribution of organic osmolytes was very limited. Consistently higher K(+) and lower Na(+) levels were found in young, as compared with old leaves, for all salinity treatments. The shoot sap K(+) progressively increased with increased salinity in old leaves; this is interpreted as evidence for the important role of free K(+) in leaf osmotic adjustment under saline conditions. A 5-fold increase in salinity level (from 100 mM to 500 mM) resulted in only a 50% increase in the sap Na(+) content, suggesting either a very strict control of xylem Na(+) loading or an efficient Na(+) removal from leaves. A very strong correlation between NaCl-induced K(+) and H(+) fluxes was observed in quinoa root, suggesting that a rapid NaCl-induced activation of H(+)-ATPase is needed to restore otherwise depolarized membrane potential and prevent further K(+) leak from the cytosol. Taken together, this work emphasizes the role of inorganic ions for osmotic adjustment in halophytes and calls for more in-depth studies of the mechanisms of vacuolar Na(+) sequestration, control of Na(+) and K(+) xylem loading, and their transport to the shoot.
我们通过将植物暴露在 6 个盐度水平（0-500mM NaCl 范围）下 70d 来研究藜麦（Chenopodium quinoa Willd.）的离子和渗透关系。盐胁迫通过在种子种植前将计算量的 NaCl 与盆栽混合物预先混合或通过逐渐增加灌溉水中的 NaCl 水平来施加。对于这两种方法，在 100mM 和 200mM NaCl 之间实现了最佳的植物生长和生物量，这表明藜麦拥有一种非常有效的系统，可以通过渗透调节来适应 NaCl 胁迫的突然增加。在这些 NaCl 水平下，通过积累无机离子（Na(+)、K(+)和 Cl(-)），老叶中实现了 95%的渗透调节，而在幼叶中实现了 80%-85%的渗透调节，而有机渗透物的贡献非常有限。对于所有盐处理，与老叶相比，在幼叶中发现了更高的 K(+)和更低的 Na(+)水平。在老叶中，随着盐度的增加，茎汁液中的 K(+)逐渐增加；这表明在盐胁迫下，游离 K(+)在叶片渗透调节中起着重要作用。盐度水平从 100mM 增加到 500mM 时，汁液中的 Na(+)含量增加了 5 倍，这表明木质部 Na(+)装载受到严格控制，或者叶片中 Na(+)被有效去除。在藜麦根中观察到 NaCl 诱导的 K(+)和 H(+)通量之间非常强的相关性，这表明需要快速的 NaCl 诱导的 H(+)-ATPase 激活，以恢复否则去极化的膜电位并防止细胞质中进一步的 K(+)泄漏。总的来说，这项工作强调了无机离子在盐生植物中渗透调节的作用，并呼吁对液泡 Na(+)隔离、Na(+)和 K(+)木质部装载的控制及其向地上部分的运输的机制进行更深入的研究。
