The photosynthetic efficiency and heavy metals levels in Silybum marianum L. treated with azoxystrobin

Silybum marianum L. (milk thistle) is valued worldwide for its medicinal properties. Currently, there is growing interest in the organic cultivation of this herb under controlled conditions. Unfortunately, its plantations are often exposed to fungal diseases, which pose a significant threat. The aim of the present study was to determine the effect of the fungicide azoxystrobin on photosynthesis and the uptake of manganese, copper, cadmium, lead, iron, and zinc by milk thistle. Moreover, using the Folin-Ciocalteu method, we determined changes in the level of phenolic compounds, which may reflect the potential response of plants to stressors. The concentrations of metals either in soil or plant samples were determined using ICP-OES technique. In general, azoxystrobin stimulated photosynthesis as indicated by the increase of gas exchange parameters which returned to initial values after 42 days of cultivation. Notable, the decrease of chlorophyl index was observed 28 days after the fungicide application. Nevertheless, the total phenolic content in milk thistle was gradually increasing over the time of cultivation. The highest influence of azoxystrobin was observed for lead and zinc which uptake by roots was significantly reduced after the fungicide application.