Influence of plant growth regulating substances on transport and degradation of acephate and its metabolite methamidophos in tomato

The occurrence of pesticides in vegetables such as tomato poses an increasing attention to their potential risk to human health. In this study, acephate and its metabolite methamidophos were investigated for their transport and degradation in tomato cultivated in spiking nutrient solutions containing acephate at 1 mg/L. Acephate was taken up and transported via xylems with the concentrations of 41–145 μg/L in xylem sap at 2 and 8 cm above the roots in control treatment. The residue levels of methamidophos derived from acephate were in a range of 0–4.21 μg/L, being 0.00–3.73% of the parent acephate. The influence of three plant growth regulating substances, 1-naphthylacetic acid (NAA), glucose and phlorizin, on the transport and degradation of acephate and methamidophos in tomato was evaluated. All of these substances had positive effects on the transport of acephate and methamidophos in tomato xylem system. The NAA or glucose treatment promoted the degradation of acephate to methamidophos; however, with the addition of phlorizin, the concentrations of acephate were reduced in comparison to that under glucose treatment, suggesting that phlorizin would cause an inhibitory effect on the transport of acephate in tomato plant. These results may indicate an effective approach to reduce acephate and methamidophos residues in tomato.