Comparison of chlorophyll fluorescence and whole‐plant bioassays of isoproturon

Abstract

Summary The response to aqueous solutions of isoproturon was examined on intact plants of Matricaria perforata , Apera spica‐venti and Sinapis alba in greenhouse tests, comparing visual estimates of shoot phytotoxicity at 30 d after application (DAA) with measurements of fast chlorophyll fluorescence induction at 10 DAA on leaves of the same treated plants. The sensitivity was greatest from pre‐emergence application to intact plants of M. perforata and A. spica‐venti , whereas post‐emergence sprays were relatively more active on S. alba . The use of fluorescence induction was investigated further in Petri‐dish experiments on excised M. perforata leaf segments. The Petri‐dish bioassay enabled detection of isoproturon at concentrations above 9 × 10 −7 M within 96 h after herbicide exposure. The potential for using chlorophyll fluorescence assays for the determination of isoproturon content in soil extracts is discussed.