School of Environmental Science and Engineering, Tianjin Polytechnic University, Tianjin, 300387, China; Department of Civil and Environmental Engineering, Shantou University, Shantou, 515063, China.
School of Environmental Science and Engineering, Tianjin Polytechnic University, Tianjin, 300387, China.
Chemosphere. 2019 Dec;237:124482. doi: 10.1016/j.chemosphere.2019.124482. Epub 2019 Jul 30.
The increase in the proportion of microplastics in the environment has intensified the interest in phthalate and microplastic contamination in recent years. In this study, we investigated the response of photosynthetic parameters and the antioxidant system of lettuce to di-n-butyl phthalate (DBP) stress and exposure to various concentrations of microplastic polyethylene (MP) for different durations (14 d and 28 d). Lettuce growth, photosynthetic parameters, and chlorophyll content were reduced significantly after MP- and DBP-only treatments and after the combined (MP + DBP) treatments with both pollutants (P < 0.05), when compared with the control. Our findings indicated that the exposure to MP can inhibit growth, hinder photosynthesis, and interfere with the antioxidant defense system in lettuce. Specifically, compared with the DBP-only treatment group, in all MP + DBP treatment groups, the lettuce growth parameters (dry and fresh weights of the leaves and roots and the number of leaves) decreased (P < 0.05). Moreover, the photosynthetic rate, stomatal conductance, transient transpiration rate, fluorescence parameters, chlorophyll content of leaves, and activity of Rubisco decreased, but the intercellular CO concentration increased in all MP + DBP treatment groups. The reduction in photosynthesis was attributed to the limitation of non-porosity and inhibition of the photoelectron flow, and the increase in exogenous MP content aggravated the effect of DBP on photosynthesis in lettuce. Compared with the DBP-only group, in all MP + DBP treatment groups, the content of superoxide radicals and hydrogen peroxide in lettuce leaves and roots increased. Antioxidant levels increased with the increase in MP content, except in the 1.0 mg mL MP treatment after 14 d. Although the antioxidant system exhibited certain protective effects in the latter treatment, the cell membranes were still damaged. The degree of damage to cells decreased with the growth of lettuce, but the damage to root tissue always remained higher than that of the leaves. In conclusion, exposure to exogenous MP exacerbated the damage to lettuce by DBP.
近年来，环境中微塑料比例的增加加剧了人们对邻苯二甲酸酯和微塑料污染的关注。在这项研究中，我们研究了生菜对邻苯二甲酸二丁酯（DBP）胁迫和暴露于不同浓度的微塑料聚乙烯（MP）不同时间（14 天和 28 天）的光合参数和抗氧化系统的反应。与对照组相比，仅用 MP 和 DBP 处理以及用两种污染物（MP+DBP）处理后，生菜的生长、光合参数和叶绿素含量均显著降低（P<0.05）。我们的研究结果表明，暴露于 MP 会抑制生菜的生长、阻碍光合作用，并干扰其抗氧化防御系统。具体来说，与仅用 DBP 处理组相比，在所有 MP+DBP 处理组中，生菜的生长参数（叶片和根系的干重和鲜重以及叶片数）均降低（P<0.05）。此外，所有 MP+DBP 处理组的光合速率、气孔导度、蒸腾速率、荧光参数、叶片叶绿素含量和 Rubisco 活性均降低，而细胞间 CO 浓度均升高。光合作用的降低归因于非多孔性的限制和光电子流的抑制，外加 MP 含量的增加加剧了 DBP 对生菜光合作用的影响。与仅用 DBP 处理组相比，在所有 MP+DBP 处理组中，生菜叶片和根系中超氧自由基和过氧化氢的含量增加。抗氧化水平随 MP 含量的增加而增加，除了在 14 天的 1.0 mg mL MP 处理中除外。尽管在后一种处理中，抗氧化系统表现出一定的保护作用，但细胞膜仍受到损伤。随着生菜的生长，细胞的损伤程度降低，但根组织的损伤始终高于叶片。总之，外源性 MP 加剧了 DBP 对生菜的损害。
