Temperature stress (cold and heat) strongly affect the phytotoxicity of polycyclic aromatic hydrocarbon (phenanthrene) to wheat

Anthropogenic activity could create different threats leading to irreversible changes in the global environment and, as a consequence, posing varied stressful conditions acting together (combined stress) on organisms. Our research concerned the combined stress of two of the main threats to soil health and plant health: temperature stress and pollution. The aim of this research was the quantitative assessment of the impact of temperature stress on the phytotoxicity of PAHs (polycyclic aromatic hydrocarbons; specifically, phenanthrene, which is a widespread, harmful organic contamination of soil) on the growth of wheat seedlings in relation to the level of soil contamination by phenanthrene (0-1000 mg kg-1 dry mass of soil) and the type of temperature stress: cold (10 degrees C) and heat (35 degrees C) stress, in three different soils. Earlier studies have investigated the effect of temperature stress on PAH toxicity mainly on soil invertebrates. However, the impact of temperature stress on PAH phytotoxicity towards crop plants, which are important for human food security but could be affected by chemical soil degradation, is still poorly understood. Our results indicated that the phenanthrene phytotoxicity was significantly enhanced by cold stress and heat stress. The effects of cold and heat temperature stress increased with increasing phenanthrene level. Our research is important for improving the risk assessment of PAH and food security forecasting.