铊和镉胁迫对芦竹生长及光合特征的影响

Effects of thallium and cadmium stress on growth and photosynthetic characteristics of Arundo donax

关键词:  植物修复, 铊, 镉, 芦竹, 光合特征

Key words:  phytoremediation, thallium, cadmium, Arundo donax, photosynthetic characteristics

摘要:

芦竹(Arundo donax)对多种重金属都有较好的耐受性,是植物修复技术较理想的选择,而关于芦竹对Cd和Tl胁迫生理反应的相关研究却较少,为了有效治理Cd和Tl的污染,本研究以芦竹为材料,通过添加不同浓度重金属Tl(4,10和20 mg·kg^-1)、Cd(50,100和200 mg·kg^-1)进行芦竹盆栽试验,测定芦竹的株高、分蘖数、叶绿素含量、光合生理指标以及Tl和Cd在芦竹中的累积量,探讨芦竹对Tl和Cd胁迫的响应机制。结果表明:Tl(4～20 mg·kg^-1)和Cd(50～200 mg·kg^-1)对芦竹株高、分蘖数以及叶绿素含量均无显著影响(P>0.05); 芦竹体内Tl和Cd含量随着Tl和Cd浓度的升高呈上升趋势,芦竹体内Tl含量的分布规律为根>茎>叶,Cd含量的分布规律:Cd浓度50 mg·kg^-1时为茎>叶>根,Cd浓度100和200 mg·kg^-1时为根>茎>叶,表明Tl和Cd主要分布在根部,芦竹对Tl、Cd有一定的富集能力。Cd和Tl处理均显著降低芦竹叶片的胞间CO₂浓度,在Tl浓度为10 mg·kg^-1时,净光合速率、气孔导度和蒸腾速率得到显著提高,当Cd浓度为50 mg·kg^-1时,净光合速率、气孔导度和蒸腾速率得到显著提高。这表明芦竹对重金属Cd和Tl有较强的耐受性,可为Cd和Tl污染土壤的治理和修复提供参考。

Abstract:

Urbanization and industrial activities have contributed to widespread contamination by heavy-metals, such as cadmium(Cd)and thallium(Tl), which have caused a series of problems to ecosystem functioning and human health. Therefore, how to effectively control the Cd and Tl pollution is one of the most urgent environmental problems. Arundo donax has a strong tolerance of a variety of heavy metals, and is an ideal choice for phytoremediation, however, there is limited information on the physiological responses of A. donax to Cd and Tl stress, regarding its highly desirable for phytoremediation of metal contaminated sites. Therefore, a potted experiment was carried out to investigate the effects of different concentrations of Cd(50, 100 and 200 mg·kg^-1)and Tl(4, 10 and 20 mg·kg^-1)stress on height, number of nodes and chlorophyll content of A. donax, photosynthetic characteristics and the accumulation of Cd and Tl in A. donax after four months of cultivation, all these parameters were determined for each treatment. The results showed that the height, number of nodes and chlorophyll content of A. donax were not significantly affected by exposure to Tl(form 4 to 20 mg·kg^-1)or Cd(form 50 to 200 mg·kg^-1)(P > 0.05). The concentrations of Tl and Cd in A. donax increased with the additive concentration of Tl and Cd, Tl accumulated in the order of root > stem > leaf; while Cd accumulated in order of stem > leaf > root under 50 mg·kg^-1 Cd concentration treatments and in order of root > stem > leaf under 100 and 200 mg·kg^-1 Cd concentration treatments, Tl and Cd are mainly distributed in the root, A. donax has certain enrichment ability to Tl and Cd. Although all Tl treatments significantly decreased intercellular CO₂ concentration(C_i)of A. donax, 10 mg·kg^-1 Tl treatment significantly increased the net photosynthetic rate(P_n), stomatal conductance(G_s)and transpiration rate(T_r). Meanwhile, all Cd treatments significantly decreased the intercellular CO₂ concentration and the water use efficiency(WUE), but 50 mg·kg^-1 treatment significantly increased the net photosynthetic rate, stomatal conductance and transpiration rate. These results suggest a strong tolerance of A. donax to increased Cd or Tl pollution and it can be used as a reference for the treatment and remediation of Cd or Tl contaminated soil.