Effects of antibiotics stress on root development, seedling growth, antioxidant status and abscisic acid level in wheat (Triticum aestivum L.).

The veterinary antibiotics contamination in agroecosystems is a substantial problem globally. However, little is known about their toxicity to crops, especially in wheat. This study evaluated the phytotoxic effects of the two most representative antibiotics, namely oxytetracycline (OTC) and enrofloxacin (ENR), on seed germination, seedling growth, root elongation and antioxidant status in wheat, and investigated the response of abscisic acid (ABA) to antibiotic stress and its underlying mechanism. The results showed that OTC and ENR under the experimental concentrations (5, 10, 20, 40 and 80 mg·L-1) had no influence on seed germination of wheat. The reduced root length, fresh weight and surface area were observed when the concentrations of OTC and ENR were higher than 10 mg·L-1 and 5 mg·L-1, respectively. High concentrations (＞40 mg·L-1) of antibiotics dramatically decreased the root length, fresh weight, root numbers and surface area as well as the number of stele cells and stele area. The activity of catalase (CAT), superoxide dismutase (SOD) and peroxidase (POD), and malondialdehyde (MDA) content in shoots and roots were increased with the increasing OTC and ENR concentrations. High concentrations (＞40 mg·L-1) of antibiotics improved ABA content and enhanced the transcription levels of genes related to ABA biosynthesis (TaNCED1 and TaNCED2) and metabolism (TaABA8'OH1-A and TaABA8'OH2-A) in shoots and roots of wheat seedlings. Wheat seedlings had relatively strong sensitivity to low concentration (5 mg·L-1) of ENR. These results suggest that OTC and ENR modulate root development and seedling growth by regulating ABA level and antioxidant defense system in wheat.