Comparison of physiological effects of fluazifop‐butyl and sethoxydim on oat (Avena sativa L.)

Abstract

Laboratory experiments were conducted to compare the physiological effects of two herbicides: fluazifop‐butyl {butyl (RS)‐2‐[4‐(5‐trifluoromethyl‐2‐pyridyloxy)phenoxy]‐propionate} and sethoxydim {(±)‐2‐[1‐(ethoxyimino)butyl]‐5‐[2‐(ethylthio)propyl]‐3‐hydroxy‐2‐cyclohexen‐1‐one} on oat (Avena sativa L. cv. Zenshin). The herbicides strongly inhibited growth of oat and induced chlorosis at the basal part of shoots and ethylene production from the seedlings. The phytotoxicity of these herbicides in oat seedlings was alleviated by 2,4‐D (2,4‐dichlorophenoxyacetic acid), but not by IAA (indole‐3‐acetic acid). Coleoptile elongation induced by 2,4‐D or IAA was inhibited by fluazifop‐butyl and sethoxydim, suggesting both herbicides possess the activity to inhibit this auxin action. Fluazifop (free acid) and sethoxydim inhibited proton excretion from oat roots but fluazifop‐butyl did not. This proton excretion was not restored by 2,4‐D or IAA. Furthermore, cellular electrolyte leakage in oat shoots was increased by both herbicides, indicating that the membrane permeability was increased. We conclude that fluazifop‐butyl and sethoxydim may have the same mechanism of action which leads to disruption of membrane integrity, although fluazifop‐butyl acts as a free acid after hydrolysis (fluazifop).

Susceptibility of a broad‐leaved weed, Acanthospermum hispidum, to the grass herbicide fluazifop‐butyl

“…In a previous paper, we reported that the first visible symptom in AOPP or CHD‐treated grass was chlorosis appearing at the basal part of shoots (Luo et al . 2001).…”

“…However, fluazifop‐butyl induced wilting and necrosis of A. hispidum leaves within 20 HAT. In addition, the period required to induce seedling death was distinctly different; approximately 15 days were necessary for oat (Luo et al . 2001), while only 48–72 h for A. hispidum (Fig.…”

“…In oat, a susceptible species, fluazifop‐butyl and sethoxydim increased the membrane permeability of shoot disks and inhibited lipid biosynthesis (Luo et al . 2001; Fig.…”

“…Two other plants, pea ( Pisum sativum L; resistant to AOPP and CHD) and oat ( Avena sativa L. cv. Zenshin; sensitive to AOPP and CHD), were used to study lipid biosynthesis and ACCase inhibition (Luo et al . 2001).…”