Comparison of sensitivity of vascular plants to six paddy rice herbicides using the seed germination and seedling growth test method for five vascular plant species simultaneously

Abstract

We compared the sensitivity based on the 50 percent effective concentrations (EC₅₀s) of five species of plant to six herbicides, using an efficient high-throughput microplate-based toxicity assay. For five herbicides, the most sensitive species differed: Welsh onion Allium fistulosum was most sensitive to cyclosulfamuron (the inhibitor of acetolactate synthase), pretilachlor (the inhibitor of very long-chain fatty acid (VLCFA) synthesis) and pyrazoxyfen (the inhibitor of 4-hydroxyphenylpyruvate dioxygenase): watercress Nasturtium officinale was most sensitive to pyraclonil (the inhibitor of protoporphyrinogen oxidase); and basil Ocimum basilicum was most sensitive to esprocarb (the inhibitor of VLCFA synthesis). Simetryn, the inhibitor of photosynthesis, was evenly less toxic, with no differences in species sensitivity. These results suggested that a single species cannot represent the sensitivity of the primary producer assemblage to a given herbicide. To assess the ecological effects of herbicides, multispecies plant toxicity data sets are essential.