Study On Enantioselective Environmental Behaviours Oftriazole Plant Growth Regulators

Triazole plant growth regulators are used widely in crops, horticulture and forestry due to their broad spectrum, high effectiveness and low toxicity to target plants. Recently, many reports have been forcusing on toxicity, mechanism and residue in soils.Until now, little is known on the differences in the inhibition effects of target plants induced by individual stereoisomers of triazole plant growth regulators. In addition, there is a potential impact on freshwater systems for widespread applications of pesticides. The input of excessive pesticides was one of most important reason that led to water bloom. But, presently there is still little information on the toxicity of triazole plant growth regulators to non-target aquatic organisms of cyanobacteria.In this study, baseline separation of paclobutrazol and uniconazole enantiomers was achieved on a Chiralcel AD-H column, and their absolute con?gurations were con?rmed by a circular dichroism (CD) detector, optical rotatory dispersion (ORD) and ultraviolet detector (UV). The concentrations of enantiomers were quantified on 6890N-GC. A method for determination of residues and enantiomeric fraction of triazole plant growth regulators in soil and water was established. Then we used the method to determinate residues and enantiomeric fraction of paclobutrazol in soil and water collected from agriculture sites in Zhejiang.The present study was therefore undertaken to evaluate the enantioselectivity of triazole plant growth regulators in phytotoxicity to target and non-target freshwater species. After 7d rice seedlings growth-inhibition tests, results showed that paclobutrazol and uniconazole inhibited the growth of rice seedlings effectively and there were enantioselective effects of triazole plant growth on plant growth. The results indicated that the S-(-)-paclobutrazol enantiomer was almost 3.09 times more toxic than the R-(+)-paclobutrazol to shoots growth and the S-(+)-uniconazole enantiomer was almost 2.63 times more toxic than the R-(-)-uniconazole enantiomer. Comparing the active of these two pesticides, we found that the inhibition active of uniconazole was 3.26 times higher than paclobutrazol. After 96 h cyanobacteria toxicity tests, the result showed that the plant growth regulators in low concentrations posed significantly stimulative effects on algae of Microcystis aeruginosa and Anabaena sp., and we also observed the enantioselectivity between enantiomers. Results indicated that the stimulus ability of the S-enantiomers of triazole plant growth regulators stimulated Microcystis aeruginosa growth were more effective than R-enantiomers. But Anabaena sp. was much different from Microcystis aeruginosa. The stimulus ability of the R-enantiomers of triazole plant growth regulators stimulated Anabaena sp. growth was more effective than S-enantiomers.According to our study, these results indicated that the widespread application of triazole plant growth regulators had the potential risks to the freshwater systems. These were also indicated that the correct application of plant growth regulators and the assessment of environmental safety should consider enantioselectivity.