For revealing the effects of NaCl and NaHCO₃ stress at different pH levels on the absorption and accumulation of main ions in roots, stems and leaves, alfalfa (Medicago sativa L.) plants were cultivated in a nutrient solution system. After NaCl and Na₂HCO₃ imposition, the contents of main ions in roots, stems, leaves and xylem bleeding sap were determined. Under NaCl and Na₂HCO₃ stresses with the same Na⁺ concentration, Na₂HCO₃ stress showed severer inhibitory effects on alfalfa growth in contrast to NaCl stress at different pH levels. Under NaCl stresses at different pH levels, alfalfa plants showed much lower Na⁺ accumulation and Na⁺ delivery rate in root bleeding sap than that under NaHCO₃ stress. The plants of NaHCO₃ stress showed a severer inhibition in K⁺ accumulation, lower K⁺ delivery rate, but higher Na⁺/K⁺ ratios than the plants of NaCl stress. NaHCO₃ stress increased Ca²⁺ and Mg²⁺ accumulation in alfalfa roots, decreased Ca²⁺ and Mg²⁺ delivery rates and increased leaf Na⁺/Ca²⁺ ratio and Na⁺/Mg²⁺ ratio. Both NaCl and NaHCO₃ stresses decreased the contents of Fe³⁺ and Mn²⁺ in roots, but increased the contents of Cu²⁺ in roots, stems and leaves, the content of Mn²⁺ in stems and leaf Zn²⁺ content in alfalfa plants. However, the contents of Fe³⁺ and Mn²⁺ in roots and stem Mn²⁺ content in the NaHCO₃ treatments were much lower than those in the NaCl treatments. In conclusion, NaHCO₃ stress produced severer injury and induced severer Na⁺ toxicity to alfalfa plants than NaCl stress. The effects of NaHCO₃ stress and NaCl stress on the absorption and accumulation of trophic ions were different. Under NaCl stress, the increased pH did not alter Na⁺ absorption and accumulation in plants, but altered the distribution of some nutrient ions in roots, stems and leaves.

中文翻译：

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不同pH值NaCl和Na2HCO3胁迫下苜蓿植株离子转运和积累的变化

为了揭示不同pH值下NaCl和NaHCO ₃胁迫对根、茎和叶中主要离子吸收和积累的影响，在营养液系统中栽培紫花苜蓿（Medicago sativa L.）植物。NaCl和Na ₂ HCO ₃施加后，测定根、茎、叶和木质部流血汁液中主要离子的含量。在相同 Na ⁺浓度的NaCl 和 Na ₂ HCO ₃应力下，Na ₂ HCO ₃与不同 pH 水平的 NaCl 胁迫相比，胁迫对紫花苜蓿的生长有更严重的抑制作用。在不同pH值的NaCl胁迫下，紫花苜蓿根系流血液中的Na ⁺积累和Na ⁺输送率均低于NaHCO ₃胁迫下。与NaCl胁迫相比，NaHCO ₃胁迫植物表现出更严重的K ⁺积累抑制，更低的K ⁺传递率，但更高的Na ⁺ /K ⁺比值。NaHCO ₃胁迫增加了苜蓿根中Ca ²⁺和Mg ^{2+ 的}积累，降低了Ca ²⁺和Mg²⁺输送率和增加的叶 Na ⁺ /Ca ²⁺比率和 Na ⁺ /Mg ²⁺比率。NaCl和NaHCO ₃胁迫均降低了根中Fe ³⁺和Mn ²⁺的含量，但增加了根、茎和叶中Cu ²⁺的含量，以及茎和叶中Mn ²⁺的含量和Zn ^{2+ 的}含量。苜蓿植物。然而，NaHCO ₃处理根中Fe ³⁺和Mn ²⁺含量和茎中Mn ²⁺含量远低于NaCl处理。总之，NaHCO ₃与 NaCl 胁迫相比，胁迫对苜蓿植株产生更严重的伤害并诱导更严重的 Na ⁺毒性。NaHCO ₃胁迫和NaCl胁迫对营养离子吸收和积累的影响不同。在NaCl胁迫下，pH值升高并未改变植物对Na ^{+ 的}吸收和积累，而是改变了部分营养离子在根、茎和叶中的分布。