Polypropylene microplastics modify copper associated leaf injury and photosynthetic responses in Nymphaea ‘Black Beauty’
Abstract
IntroductionMicroplastics and heavy metals cooccur in freshwater habitats, yet it remains unclear whether microplastics intensify metal toxicity or redirect the dominant mode of plant injury.MethodsWe exposed the floatingleaved aquatic plant Nymphaea `Black Beauty' for 28 d to control conditions, copper (Cu) alone, polypropylene microplastics (PPMPs) alone, or combined Cu and PPMP stress. Wholeplant phenotype, relative growth rate, leaf chlorosis and necrosis, root scanning electron microscopy, gas exchange, chlorophyll fluorescence, malondialdehyde (MDA), and antioxidant enzymes were integrated to distinguish structural damage from functional inhibition.ResultsCu alone produced a necrosisdominated response: relative growth rate decreased by approximately 65%, net photosynthetic rate (Pn) by 54%, effective PSII quantum yield (ΦPSII) by 52%, and electron transport rate (ETR) by 47%, whereas MDA increased by 58% and necrotic area reached 26.4%. PPMPs alone caused moderate growth inhibition and chlorosis, with a numerically higher nonphotochemical quenching (NPQ) mean and little lipid peroxidation. Factorial analysis detected Cu × PP interactions for selected endpoints, including growth, necrosis, Pn, NPQ, ETR, and POD; these endpointwise tests were exploratory. Necrotic area declined to 2.1%, but growth and photosynthesis remained strongly inhibited. The density of morphologically assigned PPlike structures in processed root sections was 4.16fold higher under combined exposure than under PPMPs alone. Under coexposure, Pn declined while no differences in stomatal conductance or transpiration from the control were detected, while ΦPSII, ETR, and NPQ decreased markedly. The lower NPQ mean was consistent with reduced regulated thermal dissipation under the measurement conditions but was not diagnostic of a specific photoprotective defect. POD activity increased by approximately 40%, whereas SOD activity decreased by 35%, showing an enzymespecific antioxidant pattern rather than demonstrating enhanced overall detoxification.DiscussionThus, under the shared 2% Tween20 background, Cu -PP coexposure produced a lownecrosis, highfunctionalinhibition phenotype consistent with an important nonstomatal component. These responses do not establish altered Cu distribution, particle internalization, or detoxification.
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BibTeX
@article{rong2026polypropylene,
title = {{Polypropylene microplastics modify copper associated leaf injury and photosynthetic responses in Nymphaea ‘Black Beauty’}},
author = {Yuhong Rong and Hongjun Mu and Zhaohao Zhang and Yanyin Xu and Yongbo Zhang and Ziyu Li and Zesen Lai and Jiang Xie and Shen Xiong and Wuchang Chen and Kaixiong Li and Shanman Li and Chao Luo},
journal = {Frontiers in Plant Science},
year = {2026},
month = nov,
doi = {10.3389/fpls.2026.1954222},
url = {https://www.frontiersin.org/articles/10.3389/fpls.2026.1954222},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Polypropylene microplastics modify copper associated leaf injury and photosynthetic responses in Nymphaea ‘Black Beauty’
AU - Yuhong Rong
AU - Hongjun Mu
AU - Zhaohao Zhang
AU - Yanyin Xu
AU - Yongbo Zhang
AU - Ziyu Li
AU - Zesen Lai
AU - Jiang Xie
AU - Shen Xiong
AU - Wuchang Chen
AU - Kaixiong Li
AU - Shanman Li
AU - Chao Luo
PY - 2026
DA - 2026/11/04
JO - Frontiers in Plant Science
DO - 10.3389/fpls.2026.1954222
UR - https://www.frontiersin.org/articles/10.3389/fpls.2026.1954222
AB - IntroductionMicroplastics and heavy metals cooccur in freshwater habitats, yet it remains unclear whether microplastics intensify metal toxicity or redirect the dominant mode of plant injury.MethodsWe exposed the floatingleaved aquatic plant Nymphaea `Black Beauty' for 28 d to control conditions, copper (Cu) alone, polypropylene microplastics (PPMPs) alone, or combined Cu and PPMP stress. Wholeplant phenotype, relative growth rate, leaf chlorosis and necrosis, root scanning electron microscopy, gas exchange, chlorophyll fluorescence, malondialdehyde (MDA), and antioxidant enzymes were integrated to distinguish structural damage from functional inhibition.ResultsCu alone produced a necrosisdominated response: relative growth rate decreased by approximately 65%, net photosynthetic rate (Pn) by 54%, effective PSII quantum yield (ΦPSII) by 52%, and electron transport rate (ETR) by 47%, whereas MDA increased by 58% and necrotic area reached 26.4%. PPMPs alone caused moderate growth inhibition and chlorosis, with a numerically higher nonphotochemical quenching (NPQ) mean and little lipid peroxidation. Factorial analysis detected Cu × PP interactions for selected endpoints, including growth, necrosis, Pn, NPQ, ETR, and POD; these endpointwise tests were exploratory. Necrotic area declined to 2.1%, but growth and photosynthesis remained strongly inhibited. The density of morphologically assigned PPlike structures in processed root sections was 4.16fold higher under combined exposure than under PPMPs alone. Under coexposure, Pn declined while no differences in stomatal conductance or transpiration from the control were detected, while ΦPSII, ETR, and NPQ decreased markedly. The lower NPQ mean was consistent with reduced regulated thermal dissipation under the measurement conditions but was not diagnostic of a specific photoprotective defect. POD activity increased by approximately 40%, whereas SOD activity decreased by 35%, showing an enzymespecific antioxidant pattern rather than demonstrating enhanced overall detoxification.DiscussionThus, under the shared 2% Tween20 background, Cu -PP coexposure produced a lownecrosis, highfunctionalinhibition phenotype consistent with an important nonstomatal component. These responses do not establish altered Cu distribution, particle internalization, or detoxification.
SN - 1664-462X
ER -