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

PÉREZ, DÉBORA JESABEL; MENONE, MIRTA LUJÁN; TOGNETTI, JORGE

Buenos Aires

Congreso; SETAC Latin America 11th Biennial Meeting; 2015

Sociedad de Toxicología y Química Ambiental Latinoamérica

Strobilurin fungicides (SF) inhibit mitochondrial respiration in pathogenic 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 between PSII and PSI in the 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 transferred to soil-containing pots and maintained in a greenhouse for growth. Two plant sets (36 plants each) were selected to exposure at different concentrations of AZX; one set of young adult plants (YAP) -two old months- and other set of pre-senescence plants (PSP) ?three old months-. Plant roots were carefully rinsed in water and immersed during 24 hs in glass 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 with dimethylformamide and CaF was measured by the ratio Fv/Fm, an indicator of the quantum yield of PSII. In addition, in PSP roots the activities of enzymatic antioxidant as Glutation-S-Transferase (GST), catalase (CAT) and peroxidase (POD) were determined in root extracts following the standard protocols. Chl concentration 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). In addition, the ratio Fv/Fm did not show statistically significant changes at different treatments in YAP and PSP. The enzymatic antioxidant activity of GST, CAT and POD did not show statistically significant changes at different treatments (p values > 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 roots of PSP the enzymatic antioxidant activity showed an increasing trend. Due to the rather low Log Kow value of AZX (2.5), the fungicide has a high translocation potential from root to leaves. Thus AZX could induce a rapid antioxidant response in root and, in parallel, effects on leaves, which may depend on the physiological status of the plants