NaCl胁迫对圆柏幼苗生长和离子吸收及分配的影响

以当年生圆柏幼苗为实验材料,采用温室调控盆栽土培法研究了不同浓度NaCl(0、100、200、300mmol·L-1)胁迫21d对其生长情况及不同器官(根、茎、叶)中K~+、Na~+、Ca~(2+)和Mg~(2+)的吸收和分配的影响,以探讨圆柏幼苗对盐环境的生长适应性及耐盐机制。结果表明:(1)随着NaCl胁迫浓度的增加,圆柏幼苗生长,包括株高、地径、相对生长量以及生物量的积累均呈下降趋势,而其根冠比却增加。(2)在各浓度NaCl胁迫处理下,圆柏幼苗根、茎、叶中Na~+含量较对照均显著增加,而且叶中Na~+含量显著高于茎和根,叶中Na~+含量是根中的5倍。(3)随着NaCl胁迫浓度的升高,圆柏幼苗各器官中K~+、Ca~(2+)和Mg~(2+)含量以及K~+/Na~+、Ca~(2+)/Na~+及Mg~(2+)/Na~+比值均呈下降趋势。(4)在NaCl胁迫条件下,圆柏幼苗根系离子吸收选择性系数SK,Na、SCa,Na、SMg,Na显著提高,茎、叶离子转运选择性系数SCa,Na、SMg,Na则逐渐降低,叶中离子转运选择性系数SK,Na则随着NaCl胁迫浓度的升高显著降低,大量Na~+进入地上部,减缓了盐胁迫对根系的伤害。研究认为,圆柏幼苗的盐适应机制主要是通过根系的补偿生长效应及茎、叶对Na~+的聚积作用来实现的,同时也与根对K~+、Ca~(2+)、Mg~(2+)的选择性运输能力增强和茎、叶稳定的K~+、Ca~(2+)、Mg~(2+)的选择性运输能力有关。

Effects of NaCl Stress on the Growth, Ion Absorption and Distribution of Juniperus chinensis Seedlings

To understand the growth adaptability and salt tolerance mechanism of Juniperus chinensis seedlings under NaCl stress, we investigated the cationic absorption and distribution in different organs (such as roots, stems and needles) of the raw J. chinensis seedlings and its biomass accumulation under different levels of NaCl (0, 100, 200, and 300 mmol·L^-1) stress through potted soil culturing in greenhouse. The results showed that: (1) with the increase of NaCl concentration, the growth including plant height, ground diameter, relative height growth and biomass accumulation were declined, while the root/shoot ratio was increased, indicating that the growth was inhibited; (2) under the NaCl stress, the Na⁺ concentrations in the roots, stems and needles of the J. chinensis seedlings were significantly increased compared with those of the contrast seedlings, and the Na⁺ concentration in the needles was significantly higher than that in stems and roots, the Na⁺ concentration in the needles was 5 fold higher in the roots; (3) with the increase of NaCl concentration, the K⁺, Ca²⁺ and Mg²⁺ contents, K⁺/Na⁺, Ca²⁺/Na⁺ and Mg²⁺/Na⁺ ratios in different organs of the seedlings were decreased; (4) under the NaCl stress, the K⁺ Na⁺ selective transportation coefficients (S_{K, Na}), Ca²⁺ Na⁺ selective transportation coefficients (S_{Ca, Na}) and Mg²⁺ Na⁺ selective transportation coefficients (S_{Mg, Na}) of the roots were significantly decreased, but the S_Ca,Na and S_Mg,Na of the stems and needles were generally decreased, while S_K,Na of the needles were significantly declined with the increase of NaCl concentration. And large amount of Na⁺ was retained in shoots, which was advantageous for reducing the damage of salt stress to roots. In conclusion, our findings suggested that the salt adaptation mechanisma of J. chinensis seedlings were primarily implemented by root growth stimulation, stems and needles Na⁺ accumulation, and are also correlated with a remarkably increased ability of K⁺, Ca²⁺ and Mg²⁺ selective transportation in roots and steadyability of K⁺, Ca²⁺ and Mg²⁺ selective transportation in stems and needles.