Abstract:

To study the mechanisms of ion distribution and uptake in canola seedlings under combined saline stress at different growth stages （early-seedling stage and late-seedling stage）， ‘Huayouza 62’ was as material. The changes of dry weight and the contents ions （Na⁺， K⁺， Ca²⁺， Mg²⁺） in root and stem-leaf of canola seedlings at different stages under different degrees of combined salinity stress were determined by a pot experiment. The results showed that the root/shoot ratio under moderate and high stress increased by 16.47% and 48.83% in the early-seedling stage compared with the low stress， and decreased by 9.06% and 45.49% in the late-seedling stage. The Na⁺ contents in the stem-leaves and roots of canola seedling increased with the increase of salinity stress， and the Na⁺ content under high stress was significantly higher than other treatments， and Na⁺ accumulated mainly in stems and leaves in the early-seedling stage while in roots in the late-seedling stage. Compared with that in the early-seedling stage， the Na⁺ content of root in the late-seedling stage increased significantly by 1.80 （low stress）， 1.80 （moderate stress） and 1.17-fold （high stress）. K⁺ was mainly accumulated in roots， and the K⁺ content of root in the late- seedling stage was significantly lower than that in the early-seedling stage， with a reduction of 65.7% （low stress）， 83.1% （moderate stress） and 67.3% （high stress）. The selective transport coefficient （S_{\mathrm{C}{\mathrm{a}}^{\mathrm{2}+},\text{?}\mathrm{N}{\mathrm{a}}^{+}}） in early-seedling stage was higher than that in late-seedling stage， and S_{{\mathrm{K}}^{+},\mathrm{N}{\mathrm{a}}^{+}}， S_{\mathrm{M}{\mathrm{g}}^{\mathrm{2}+},\text{?}\mathrm{N}{\mathrm{a}}^{+}\text{?}}in early-seedling stage were lower than those in late-seedling stage. Salt tolerance mechanisms of ion homeostasis in early-seedling and late-seedling stages of canola were different under combined salt stress. In the early-seedling stage， Na⁺ accumulated mainly in the stem and leaves， which preferentially promoted root growth and development and increased the selective transport of Ca²⁺ from the roots to the stem and leaves to alleviate salinity stress. In the late-seedling stage， salt tolerance was improved by accumulating more Na⁺ in the roots and reducing Na⁺ accumulation in the stem and leaves， and increasing root uptake of K⁺ and Ca²⁺ and the selective transport of K⁺ and Mg²⁺ from the roots to the stem and leaves. Above results provided a theoretical basis for rapeseed planting in saline-alkali land.

Key words: saline-alkali stress, early seedling stage, late seedling stage, ion absorption and transportation, ion homeostasis

摘要：

为探究油菜苗期不同生长阶段（苗前期与苗后期）体内离子吸收及分配对复合盐碱胁迫的响应机制，以‘华油杂62号’为材料，采用盆栽方法，分析复合盐碱胁迫下离子（Na⁺、K⁺、Ca²⁺、Mg²⁺）在油菜苗期不同器官吸收及分布的变化。结果表明，油菜苗前期在中度、重度盐碱处理下，根冠比较轻度处理分别增加16.47%、48.83%，而苗后期分别降低9.06%、45.49%；随盐碱程度的增加，油菜苗期各部位Na⁺含量均呈增加趋势，重度盐碱处理下Na⁺含量均显著高于轻度和中度处理，且苗前期Na⁺主要积累于茎叶，苗后期主要积累于根部；根中Na⁺含量在苗后期显著大于苗前期，分别增加1.80（轻度）、1.80（中度）和1.17倍（重度）；K⁺主要积累于根部，苗后期根中的K⁺含量显著低于苗前期，分别降低65.7%（轻度）、83.1%（中度）和67.3%（重度）；选择性运输系数S_{\mathrm{C}{\mathrm{a}}^{\mathrm{2}+},\text{??}\mathrm{N}{\mathrm{a}}^{+}}表现为苗前期>苗后期，而S_{{\mathrm{K}}^{+},\text{??}\mathrm{N}{\mathrm{a}}^{+}}和S_{\mathrm{M}{\mathrm{g}}^{\mathrm{2}+},\text{??}\mathrm{N}{\mathrm{a}}^{+}\text{?}}表现为苗前期<苗后期。由此可见，油菜苗前期与苗后期的离子平衡耐盐碱机制可能不同；苗前期根中Na⁺含量小于茎叶，优先促进根系生长发育，同时增加根部向茎叶选择性运输Ca²⁺以缓解盐碱胁迫；而苗后期根中Na⁺含量大于茎叶，茎叶Na⁺含量减少，同时增加根部对K⁺、Ca²⁺吸收以及根部向茎叶选择性运输K⁺、Mg²⁺，以提高其耐盐性，为油菜在盐碱地的种植提供理论依据。

关键词: 盐碱胁迫, 苗前期, 苗后期, 离子吸收与运输, 离子平衡