Physiological effects of the fungicide azoxystrobin on wheat seedlings under extreme heat

Abstract

Azoxystrobin (AZ) is not only a fungicide used for disease control, but also a protective chemical for crops against specific stresses. The physiological mechanism of the fungicide AZ in protecting against heat (HT, 46 °C) stress in wheat (Triticum aestivum L.) seedlings was investigated. 'Taichung SEL-2' variety seedlings were pretreated with 0.4, 4, 40, 80, and 120 mg L-1 of AZ for 4 d. Next AZ-pretreated and untreated seedlings were subjected to HT for 1 h followed by 1000 μmol m-2 s-1 lighting for 20 min. HT induced oxidant stress which resulted in a decrease in the reducing power, an increase in malondialdehyde, and enhanced enzyme activities of ascorbate peroxidase (APX) and catalase (CAT) in leaves of untreated seedlings. However, AZpretreated seedlings under HT displayed reductions in chlorophyll fluorescence, APX and CAT activities, and the 1,1- diphenyl-2-picryl-hydrazyl scavenging capacity. Physiological damage caused by HT was aggravated by an increase in the AZ concentration. In addition, increased photosynthetic pigments were also observed in leaves of AZ-pretreated and HT-exposed seedlings. The results suggest that AZ does not provide a protective effect against HT stress.