Azoxystrobin short-time exposure effects on photosynthetic parameters in Bidens laevis L

PÉREZ, DÉBORA J; MENONE, MIRTA L; TOGNETTI, JORGE

Buenos Aires

Congreso; SETAC Latinamerica 11th Biennal Meeting; 2015

SETAC LA

Strobilurin fungicides (SF) inhibit mitochondrial respiration in fungi by blocking electron transfer. In plants, SF appear to increase chlorophyll content (Chl) and delay senescence, possibly through induction of cytokinin synthesis and enhanced antioxidant capacity. However, other evidence suggest that shortly after exposure to SF plants may be stressed, as revealed by decrease in chlorophyll a fluorescence (CaF), possibly because of blocked transport of electrons in chloroplast. The aim of this work was to evaluate the effect of azoxystrobin (AZX) on photosynthetic and antioxidant biomarkers in the hydrophyte Bidens laevis L. shortly after exposure to the fungicide. Seeds of B. laevis were collected in La Brava Lake, Argentina, in May 2012. Seeds were sterilized and placed in Petri dishes for germination. Seedlings were maintained in a greenhouse in soil pots for growth. Two plant sets (36 plants each) were selected to exposure at different concentrations of AZX; one set of young adult plants (YAP) and other set of pre-senescence plants (PSP). Plant roots were rinsed in water and immersed during 24 hs in flasks containing 330 mL of a treatment solution: 0, 0.1, 1, 10, 50 and 100 μg/L AZX (n=6). The Chl was measured by chemical extraction and CaF was measured by the ratio Fv/Fm (quantum yield of PSII). The activities of enzymatic antioxidant as Glutation-S-Transferase (GST), catalase (CAT) and peroxidase (POD) were determined in PSP root extracts following standard protocols. Chl content was unchanged with different AZX treatments in YAP (p value = 0.2075), but a statistically significant decrease in Chl in PSP exposed from 1 to 100 ug/L AZX was observed (p value = 0.0006). The ratio Fv/Fm did not show significant changes at any treatments in YAP and PSP. The enzymatic activity of GST, CAT and POD did not show statistically significant changes at any treatments (p value > 0.05), but a trend to higher activities with increasing AZX concentration was found. Early effects of AZX in B. laevis included a decrease in Chl concentration in PSP, while no significant effects on Fv/Fm were found in either YAP or PSP. In PSP roots, the enzymatic antioxidant activity showed an increasing trend. Due to their rather low Log Kow value (2.5), AZX has a high translocation potential from root to leaves. Thus AZX could induce a rapid antioxidant response in root and effects on leaves, which may depend on the plant physiological status.