Plant Physiology and Biochemistry 201 (2023) 107811 Available online 4 June 2023 0981-9428/© 2023 Elsevier Masson SAS. All rights reserved. Combined toxicity influence of polypropylene microplastics and di-2-ethylhexyl phthalate on physiological-biochemical characteristics of cucumber (Cucumis sativus L.) Haoyan Xiao a, b, 1 , Yanji Liu a, 1 , Hanxia Yu a, b, c, ** , Niraj Yadav b , Jing He b , Lige Zhang a , Wenbing Tan c, * a School of Geographical Sciences, School of Carbon Neutrality Future Technology, Fujian Normal University, Fuzhou, 350117, China b Hawkesbury Institute for the Environment, Western Sydney University, Locked Bag 1797, Penrith, NSW, 2751, Australia c State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China A R T I C L E INFO Handling Editor: Marcel K. Jansen Keywords: Microplastics Di (2-ethylhexyl) phthalate Cucumber Combined toxicity Antagonistic effect ABSTRACT Microplastics and di-2-ethylhexyl phthalate (DEHP) are prevalent and emerging pollutants in agro-ecosystem, raising concerns due to their widespread co-presence. Nevertheless, their combined toxicity on terrestrial plants remains largely unexplored. This study investigated the impact of polypropylene microplastics (MPs), DEHP, and their mixture on the physiological and biochemical characteristics of cucumber seedlings. The changes of membrane stability index (MSI), antioxidase activities, photosynthetic pigments and chlorophyll fluorescence in cucumber seedlings were assessed. The results demonstrated that MPs alone significantly inhibited MSI, photosynthetic pigments (Chl a, Chl b, and Chl a + b), F m and q p of cucumber seedlings, and significantly promoted the carotene content and antioxidant enzyme activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) in cucumber seedlings. While DEHP alone significantly inhibited MSI and photosynthetic pigments of cucumber seedlings, and significantly promoted antioxidant enzyme activities in cucumber seedlings. Moreover, the combined toxicity of MPs and DEHP was found to be less pronounced than that of the single action of MPs and DEHP. The interaction between DEHP and MPs may contribute to the reduced toxicity. Abbott’s modeling revealed that the combined toxicity systems were all antagonistic (RI < 1). Two-factor analysis and principal component analysis further confirmed that the treatment of MPs alone contributed the most to the toxicological effects of the physiological properties of cu- cumbers. In summary, this study highlighted the importance of understanding the combined effects of MPs and DEHP on plant physiology, providing insights for the development of effective treatments for emerging pollut- ants in agricultural ecosystems. 1. Introduction Due to their low cost, high durability, portability, and good ductility, plastics have become indispensable in daily life, industry, and agricul- tural production, leading to a significant increase in production and consumption (Sharma et al., 2020). Alarmingly, global plastic produc- tion is projected to reach 33 billion tonnes by 2050 (Sharma et al., 2020). However, only about 55% of plastic waste is suitable for recy- cling (Eriksen et al., 2019), resulting in a substantial pollution problem caused by the plastic waste. Microplastics, small plastic particles or fragments less than 5 mm in size, were listed by the United Nations Environment Programme (UNEP) in 2004 as one of the top ten envi- ronmental problems worldwide (Thompson et al., 2004). Their small size, long degradation cycle, high uptake by organisms, and subsequent transfer and enrichment in the food chain contribute to this ranking (Wang et al., 2022b). While most existing researches on microplastics pollution focused on aquatic ecosystems, recent findings reveal that the accumulation of microplastics on land is much higher than in marine * Corresponding author. ** Corresponding author. School of Geographical Sciences, School of Carbon Neutrality Future Technology, Fujian Normal University, Fuzhou, 350117 China. E-mail addresses: H.Yu@westernsydney.edu.au (H. Yu), wenbingtan@126.com (W. Tan). 1 Contributed equally to this work. Contents lists available at ScienceDirect Plant Physiology and Biochemistry journal homepage: www.elsevier.com/locate/plaphy https://doi.org/10.1016/j.plaphy.2023.107811 Received 28 February 2023; Received in revised form 29 May 2023; Accepted 31 May 2023