Phytotoxicity of atrazine combined with cadmium on photosynthetic apparatus of the emergent plant species Iris pseudacorus.

Qinghai Wang,Lei Peng,Dongyu Xie,Xiaoe Que,Cui Li,Chuansheng Chen

doi:10.1007/s11356-021-18107-9

Abstract

The combined pollution, instead of single pollution, has become a widespread contamination phenomenon in aquatic environment. However, little information is now available about the joint effects of the combined pollution, especially co-existed pesticides and heavy metals, on aquatic plants. In the present study, using continuous excitation chlorophyll fluorescence parameters and the OJIP transient, comparisons of herbicide atrazine (ATZ) phytotoxicity on Iris pseudacorus between in the presence and absence of cadmium (Cd) were evaluated over an exposure period of three weeks under laboratory conditions. Results showed that both ATZ and Cd were toxic to I. pseudacorus. The ratio Fv/Fo, specific electron transport energy (ET0/RC), and photochemistry efficiency (PIabs and PItotal) of this emergent plant species at individual ATZ and Cd concentrations were significantly lower than those of the control. ATZ mainly inhibited electron transport beyond QA at PSII acceptor side as indicated by the sharp rise of the J-step level of fluorescence rise kinetics. A pronounced K-step and the loss of I-step due to the damage on the OEC and PSI also occurred when ATZ was at or above 1.0mg·L-1. In comparison to ATZ alone, ATZ combined with Cd resulted in a lower amplitude rise in J-step with apparent J-I and I-P phases; and significantly lower Fo with higher Fv/Fo, as well as greater ET0/RC with higher values of PIabs and PItotal. However, the adverse influences of ATZ combined with Cd on the above indicators were still significant as compared with the control. Therefore, the coexistence of Cd alleviated the individual phytotoxicities of ATZ, whereas combined pollution of ATZ and Cd still induced the decline in photosynthetic performance of I. pseudacorus, and its potential ecological impacts on the aquatic vegetation cannot be ignored. Our findings offer a better understanding of the joint effects of the pesticide and heavy metal on non-target aquatic plants, and provided valuable insights into the interaction of these pollutants in aquatic environment.

Highlights

Atrazine (ATZ), a triazinic herbicide, is the second most widely consumed pesticide worldwide (Singh et al 2018)
The coexistence of Cd alleviated the individual phytotoxicities of ATZ, whereas combined pollution of ATZ and Cd still induced the decline in photosynthetic performance of I. pseudacorus, and its potential ecological impacts on the aquatic vegetation cannot be ignored
Our findings offer a better understanding of the joint effects of the pesticide and heavy metal on non-target aquatic plants, and provided valuable insights into the interaction of these pollutants in aquatic environment

Summary

Introduction

Atrazine (ATZ), a triazinic herbicide, is the second most widely consumed pesticide worldwide (Singh et al 2018). The amount of Cd occurring in water is generally less than 1 mg L− 1 (Das and Jana 2004; Bhardwaj et al 2020), whereas extraordinarily high concentrations of total Cd up to 5 mg L− 1 in waters have been reported (Thornton and Walsh 2001) Such concentrations potentially pose a threat to human health because of its harmful effects on the food chain (Das and Jana 2004). Considering that the co-presence of pesticides and heavy metals in aquatic systems has become a widespread contamination phenomenon, interactions between them may influence the fate of these pollutants, the ecotoxicological effects of one contaminant may be enhanced (synergism) or eliminated (antagonism) due to the presence of others (Starling et al 2019)

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