短期NaCl胁迫对西伯利亚白刺幼苗Na~+、K~+分配和平衡的影响

目的]为探究西伯利亚白刺盐适应机制。方法]以1年生西伯利亚白刺水培幼苗为材料,研究不同浓度NaCl(0、200、300 mmol·L-1)胁迫24 h后根系Na~+、K~+离子流的动态变化(利用扫描离子选择微电极技术,SIET)及植株各器官中Na~+、K~+含量的静态变化(利用电感耦合等离子体光谱仪,ICP-OES)。结果]表明:(1)短期NaCl胁迫显著提高了西伯利亚白刺根、茎、叶中Na~+含量,其中,叶中Na~+含量是根中的3倍以上;西伯利亚白刺根、茎、叶中K~+含量保持稳定或上升;(2)盐胁迫下,西伯利亚白刺根、茎、叶中K~+/Na~+呈下降趋势,其中,在200、300 mmol·L-1NaCl胁迫下,根中K~+/Na~+差异不显著;(3)离子流结果显示,NaCl胁迫显著提高了西伯利亚白刺根系Na~+的外流;对照和200 mmol·L-1NaCl胁迫下,K~+净流量分别为156、159 pmol·cm-2·s-1,差异不显著;300 mmol·L-1NaCl胁迫显著提高了K~+的内流,净流量为-370 pmol·cm-2·s-1。结论]综合分析认为,西伯利亚白刺通过叶片对Na~+区隔,加强根系对Na~+的外排和K~+内流,进而维持植株根系K~+/Na~+的相对平衡,以此适应盐渍环境。

Effects of Short-time Salt Stress on Distribution and Balance of Na+ and K+ in Nitraria sibirica Pall. Seedlings

Objective] To explore the salt adaptation mechanism of Nitraria sibirica Pall. Method] The net fluxes of Na⁺ and K⁺ from apex root (using scanning ion-selective electrode technique) and the contents of Na⁺ and K⁺ in different organs (using ICP-OES Spectrpmeter) were investigated in N. sibirica seedlings under the stress of different NaCl concentration (0, 200 and 300 mmol·L^-1) for 24 hours. Result] (1) Short-term NaCl stress significantly increased Na⁺ content in roots, stems, and leaves of N. sibirica seedlings, and the Na⁺ content in leaves was three times that in roots; the content of K⁺ in roots, stems, and leaves of N. sibirica seedlings remained stable or increased. (2) The K⁺/Na⁺ ration in roots, stems, and leaves of N. sibirica seedlings decreased under salt stress. The K⁺/Na⁺ ration in roots showed no significant difference under 200 or 300 mmol·L^-1 NaCl stress. (3) The results of ion fiux showed that NaCl stress significantly increased the Na⁺ efflux in roots. The net K⁺ fluxes of control and 200 mmol·L^-1 NaCl stress were 156 pmol·cm^-2·s^-1 and 159 pmol·cm^-2·s^-1 respectively, and no significant difference was observed. 300 mmol·L^-1 NaCl stress significantly increased the influx of K⁺, the net K⁺ flux was -370 pmol·cm^-2·s^-1. Conclusion] In conclusion, N. sibirica can efficiently sequestrate Na⁺ into leaves, as well as strengthen the roots Na⁺ efflux and K⁺ influx ability, and thus maintains the relative balance of K⁺/Na⁺ in plant root, so as to adapt to the salty environment.