盐镉互作下盐地碱蓬和碱蓬生长及镉吸收的比较研究

Comparative study on the growth and Cd uptake of Suaeda salsa and Suaeda glauca under the stress of salt and Cd and their interaction

  • 摘要: 利用盐生植物修复盐碱地重金属污染是一种经济有效且安全性高的生物修复方法, 但盐和重金属互作对不同盐生植物生长和重金属元素吸收的研究不足。本研究采用水培试验, 比较盐和镉互作对典型聚盐盐生植物盐地碱蓬(Suaeda salsa)和碱蓬(Suaeda glauca)生长及对重金属Cd吸收的影响, 分析盐对镉吸收的调节作用。试验设置两个盐水平(0 g∙L−1、10 g∙L−1 NaCl)和两个Cd水平(0 mg∙L−1、5 mg∙L−1 Cd), 共4个处理。研究结果表明, Cd处理显著抑制两种植物的生长, 降低了叶片肉质化程度和根冠比, 且对盐地碱蓬的抑制作用大于碱蓬, 对根部的抑制更明显。10 g∙L−1 NaCl盐处理均促进两种植物地上部的生长, 且对盐地碱蓬地上部生长的促进作用显著大于碱蓬; 但显著抑制碱蓬根系的生长。Cd处理下施加NaCl显著缓解Cd对两种植物的抑制作用, 且对盐地碱蓬的缓解作用大于碱蓬, 对Cd抑制盐地碱蓬根系生长的缓解作用为极显著。盐地碱蓬和碱蓬地上部Cd含量差异不显著, 盐处理显著降低两种植物地上部Cd含量。盐处理显著促进两种植物地上部对Na+的吸收, 盐地碱蓬地上部Na+含量和Na+/Cd高于碱蓬, 但K+含量、K+/Na+和K+/Cd显著低于碱蓬, 且Cd处理进一步促进了两种植物地上部对Na+的吸收; 盐处理降低K+的吸收和K+/Na+, 碱蓬地上部K+的吸收和K+/Na+均大于盐地碱蓬。盐、Cd处理下两种植物间地上部脯氨酸含量差异不明显, 但盐、Cd及其互作有增加地上部脯氨酸含量的趋势。在无胁迫和单一Cd处理下, 盐地碱蓬地上部可溶性糖含量显著高于碱蓬; 盐处理显著降低了盐地碱蓬地上部可溶性糖含量, Cd处理显著增加了碱蓬地上部可溶性糖的含量。上述结果表明, 盐地碱蓬和碱蓬的生长对盐、Cd及其互作的响应不同, 盐分可以缓解Cd对其生长的抑制作用, 特别是Cd对盐地碱蓬根系生长的抑制作用, 盐地碱蓬更趋向于积累无机渗透调节物质如Na+, 而碱蓬更趋向于积累无机渗透调节物质(K+)和有机渗透调节物质(可溶性糖)来抵御盐、镉胁迫。

     

    Abstract: Remediation of heavy metal-contaminated saline-alkali soil by halophytes is a cost-effective and environmentally friendly method, but there is less information on the comparative study of different halophytic species under salt and heavy metal stresses. In this study, hydroponic experiments were conducted to compare the effects of salt and Cd interactions on the growth and Cd uptake between two typical leaf succulent halophytes, Suaeda salsa and Suaeda glauca, and to explore the regulatory effect of salt on Cd absorption. There were four treatments with two salt levels (0 and 10 g·L−1 NaCl) and two Cd levels (0 and 5 mg·L−1 Cd). The results showed that Cd treatment significantly inhibited the growth of the two plants and reduced leaf succulence and root-to-shoot ratio. Additionally, the inhibitory effect was greater on S. salsa than on S. glauca, especially with respect to root growth. Salt treatment promoted the shoot growth of both plants, and the promotion effect on shoot growth was significantly greater in S. salsa than in S. glauca. However, the root growth of S. glauca was significantly inhibited. The salt treatment under Cd stress significantly alleviated the inhibitory effect of Cd on the growth of both plants, and the alleviation effect on S. salsa was greater than that of S. glauca, especially on the root growth of S. salsa. There was no significant difference in shoot Cd content between S. salsa and S. glauca under Cd stress, but the Cd content in the shoots of the two plants was significantly reduced by salt treatment. The Na+ content and Na+/Cd ratio in the shoots of S. salsa were higher than those in S. glauca, but the K+ content, K+/Na+ ratio, and K+/Cd ratio were significantly lower than those in S. glauca. Salt treatment significantly promoted Na+ absorption in the shoots of both plants, and Cd treatment further promoted Na+ absorption in the shoots. Salt treatment reduced shoot K+ content and K+/Na+ ratio in both plants; these values were higher in S. glauca than in S. salsa. There was a tendency for shoot proline content to increase in both species under salt and Cd stresses, but there were no significant differences among species, salt, and Cd treatments. The shoot soluble sugar content of S. salsa was significantly higher than that of S. glauca under no stress and Cd treatment. Salt treatment significantly decreased the shoot soluble sugar content of S. salsa and increased that of S. glauca. Cd treatment increased the shoot soluble sugar content in both species, especially that in S. glauca. The above results show that the growth of S. salsa and S. glauca have different responses to salt, Cd, and their interactions. Salt can alleviate the inhibitory effect of Cd on growth, especially the inhibitory effect of Cd on root growth of S. salsa. S. salsa tends to accumulate inorganic osmotic regulators such as Na+, whereas S. glauca tends to accumulate inorganic osmotic regulators such as K+ and organic osmotic regulators such as soluble sugars to resist salt and Cd stress.

     

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