Pharmaceutical and personal care products-induced stress symptoms and detoxification mechanisms in cucumber plants

Abstract

Contamination of agricultural soils by pharmaceutical and personal care products (PPCPs) resulting from the application of treated wastewater, biosolids and animal wastes constitutes a potential environmental risk in many countries. To date a handful of studies have considered the phytotoxicity of individual PPCPs in crop plants, however, little is known about the effect of PPCPs as mixtures at environmentally relevant levels. This study investigated the uptake and transport, physiological responses and detoxification of a mixture of 17 PPCPs in cucumber seedlings. All PPCPs were detected at higher concentrations in roots compared to leaves, with root activity inhibited in a dose-dependent manner. At 5-50 μg/L, the mature leaves exhibited burnt edges as well as a reduction in photosynthesis pigments. Reactive oxygen species (ROS) production and lipid peroxidation increased with increasing PPCP concentrations; and their contents were greater in roots than in leaves for all PPCP treatments. Enzymes involved in various functions, including oxidative stress (superoxide dismutase and ascorbate peroxidase) and xenobiotic metabolism (peroxidase and glutathione S-transferase), were elevated to different levels depending on the PPCP concentration. Glutathione content gradually increased in leaves, while a maxima occurred at 0.5 μg L PPCPs in roots, followed by a decrease thereafter. This study illustrated the complexity of phytotoxicity after exposure to PPCP mixtures, and provided insights into the molecular mechanisms likely responsible for the detoxification of PPCPs in higher plants.

Effect of low-dose, repeated exposure of contaminants of emerging concern on plant development and hormone homeostasis

“…investigated oxidative stress in cucumbers exposed to a mixture of 17 PPCPs and found changes in ROS levels at much lower concentrations than that of morphological effects, indicating the sensitivity of this measurement. Similar toChristou et al (2016), ROS production was found to coincide with an increase in membrane damage and lipid peroxidation in cucumber plants, suggesting the connection between ROS and its consequential damage to cell membranes(Sun et al, 2018a). The results that mixtures further enhanced oxidative stress and membrane damage suggest that studies using individual PPCPs might underestimate the impact of CECs on plant growth and points to the need to consider mixtures of low concentration CECs that are more reflective of treated wastewater effluents.Decreased concentrations of chlorophylls and carotenoids of lettuce seedlings cultivated in environmentally relevant concentrations of several pharmaceuticals were observed by D'Abrosca et al (2008).…”

“…exposures to individual compounds. In addition, the mixed CEC treatment caused a 2fold increase in MDA content in the roots, indicating significant cell membrane damage(Christou et al, 2016) Sun et al (2018a). investigated oxidative stress in cucumbers exposed to a mixture of 17 PPCPs and found changes in ROS levels at much lower concentrations than that of morphological effects, indicating the sensitivity of this measurement.…”

Pharmaceuticals in treated wastewater induce a stress response in tomato plants

“…The concentration of pollutants was well above that found in treated wastewater in order to enhance the stress response and to identify the processes involved. In a comparable experiment, published in 2018 24 , cucumber seedlings in a hydroponic setting were exposed to a mixture of 17 pollutants (including CBZ and DZP) at concentrations of 0, 0.5, 5 and 50 μg/l. At 0.5 and 5 μg/l, ROS levels in roots and shoots increased several folds.…”

“…Changes in molecular stress markers such as HSPs, MAPKs, GABA shunt enzymes, GABA and amino acids, were conspicuous in leaf and root of tomato seedlings treated with a cocktail of pharmaceutical compounds (CBZ, LTG, VAL, PHY, DZP) and with CBZ alone. In an experiment conceptually similar to ours 24 , cucumber seedlings in a hydroponic setting were exposed to a mixture of 17 pollutants (including DZP and CBZ), at concentrations of 0, 0.5, 5 and 50 μg/l. At 0.5 and 5 μg/l, ROS levels in roots and shoots increased several folds.…”

“…It appears that many compounds remaining in treated wastewater induce detoxification processes in plants, which include enhanced activities of detoxification enzymes such as superoxide dismutase, peroxidase and glutathione-S-transferase 23,24 . Lately, it was asked whether these pollutants could be considered as plant stressors 25 .…”