Migration Of Acephate In Tomato Plants And The Metabolic Mechanism Of Tomato Fruit

The aim of the present study is to investigate the migration and metabolic mechanism of acephate,a systemic insecticide,in tomato plants and fruits.As a starting point,we proposed a simultaneous detection method to determine the enantiomers in tomato of both acephate and its metabolite,methamidophos.The metabolic and migration pattern of acephate in tomato plant were studied by girdling,and that in tomato fruit was studied by adding procyanidin and transcriptome sequencing.This article has a theoretical and guiding significance for the efficient and safe use of pesticides in agricultural production.The specific results are as follows:1.A detection method of acephate and methamidophos enantiomers in GC-FPD was established by that way the recovery rates of acephate in tomato fruits were between 83.98%~118.56% while its added concentrations were between 0.025~2.5 mg/kg,with the relative standard deviations between 1.96%~6.01%.Likewise,those rates of methamidophos were between 81.06%~102.23%,while its added concentrations were between 0.025~2.5 mg/kg,with deviations between2.69% ~ 6.54%.In tomato plants,when the initially added concetrations of acephate and methamidophos were the same as above,however,the recovery rates of them ranged from 80.81%~117.73%,80.21%~95.19%,with their deviations from 3.01%~10.89%,1.66%~7.55%,respectively.The minimum detection limits(S / N = 10)of methamidophos R-(+)and S-(-)were 0.005 mg / kg and 0.006 mg / kg,respectively,those of methacylamine were 0.010 mg / kg and 0.010 mg / kg.As a result,the accuracy and precision of this method can absolutely meet the residual analysis requirements of methacillanamine and methamidophos in tomato samples.2.It was found that the chemical girdling in the petiole significantly reduced the migration and transport of acephate in tomato plants,especially reduced the downward transport but could not completely block it.The results indicated that the transport of acephate from the leaves to stems was completed its phloem and the xylem,more by phloem than xylem.Moreover,compared with the control group,there was no significant difference in the content of methamidophos after girdling,indicating that the route of transport between the leaves and the stem may be mainly through the xylem.In the root irrigation experiment,it was found that the upward transport of from the root was done through its xylem,and,there were selective difference in the absorption and transport between its two enantiomers in tomato plant with the transport rate of the S-(-)higher than R-(+).However,the concentration of methamidophos,product of acephate,in the girdling group was lower than that in the control group,and the concentration of methanamine R-(+)was significantly higher than that of S-(-),indicating that there may be a selective difference in the metabolism of acephate in tomato,which is more likely to be degraded as R-(+)methylamine phosphorus.The ratio of methamidophos to acephate in the fruit of the control group was smaller than that of the girdling group,which demonstrated that the ring cutting treatment reduced the metabolism of methamidophos in tomato plants.3.The effect of procyanidins on the degradation of acephate in tomato fruit was studied by adding procyanidins to the fruit.With one group adding both procyanidins and acephate,the other adding only acephate into pure water,the results showed that the hydrolyses was slow in 48 h of the first group,and there was no significant difference between those two groups:both produced no methamidophos.In the tomato fruit,the content of methamidophos in tomato fruit was 0.146 mg / kg after 48 h of injection in the control group,while in the experimental group was 0.186 mg / kg,absolutely higher than the control group,proving that procyanidins promote the degradation of acephate in tomato fruit,which may be related to the function of procyanidins to eliminate free radicals.4.The metabolic mechanism of acephate in tomato fruit was studied by transcriptome sequencing analysis,then the 15 different genes were obtained,consulting those 15 genes about their revolved reactions in tomato,combined with the difference between the two molecular structures of acephate and methamidophos,finally we got two genes that may participate in the acephate degradation: GCH1(GTP cyclohydrolase 1),CPA(N-carbamoylputrescine amidase).