Irrigation with reclaimed water containing Diclofenac and Lamotrigine induces stress reactions in Lettuce (Lactuca sativa)

Pharmaceuticals as contaminants in treated wastewater can become a serious problem for food safety when they are used for agricultural irrigation. These organic contaminants can be taken up by plants and trigger abiotic stress responses which can eventually affect plant growth and development. When crops are irrigated with treated wastewater they can take up environmentally persistent pharmaceuticals, like diclofenac and lamotrigine. In a greenhouse study the uptake and translocation of the two pharmaceuticals in lettuce (Lactuca sativa) was quantified. Furthermore, molecular and physiological changes triggered by the pharmaca were scrutinized. Plants were cultivated under controlled conditions and treated independently with diclofenac (20 µg L 1) and lamotrigine (60 µg L-1) for 48 h. While translocation of both compounds into the aerial parts of the plants was low under the conditions applied, the expression of stress related genes increased under some of the treatments, especially with diclofenac. An oxidative burst in roots and especially in leaves occurred after treatment with lamotrigine. This could be responsible for the significantly changed gene expression pattern in both tissues. Our results showed for the first time that pharmaceuticals like lamotrigine or diclofenac might act as signals for physiological alterations in crops, affecting the expression of stress related genes and possibly causing a repressed physiological status of the plant. Hence irrigation of crops with reclaimed water containing pharmaceuticals should be critically investigated with respect to plant health and performance, and potential risks for consumers.