Studies On Translocation Mechanism And Application Of Pesticides In Woody Plant

The residues of dichlorvos and omethoate in the three woody plant species (Populus alba var bolleana, Sophora japonica and Malus pumilla), were extracted for the first time by means of the Supercritical Fluid Extraction (SFE) using carbon dioxide in this experiment. According to orthogonal experiments, the optimum conditions for co-extraction were 80C, 5000PSI, 18m1 of C02, with 750 ii hg modifier(methanol) added to the extraction cell, 25mm static and 30mm dynamic extraction with acetone, the logical extraction efficiency of dichlorvos and omethoate were 116.47% and 102.39% respectively. The addition recovery demonstrated that the recovery, accuracy, precision and sensibility of the method satisfied the standards of pesticide residue analysis.Determinations of dichlorvos and omethoate were successfully performed by Capillary Gas Chromatography, the standard curves of dichlorvos and omethoate are Y-137.51+150.05X (R0.998) and Y14.81+733.55X (R0.998), and the limit minimum -quantitative and the lowest detection concentration of omethoate, which reached to 0.lSng and 2.5 X 10~7g/ml respectively, for dichlorvos the qualities are 0.OOSng and 8.33 X 109g/ml respectively.Omethoate and dichlorvos in the trunk of P. a!ba var bolleana were mainly transferred and transmitted in the late xylem tissues of the current year, some were transferred in phloem and cambium; The pesticides were mainly distributed in mesophyll tissue, some in vein; But the amount distributed on the edge and in the center of leaves showed no obvious difference. In S. Japonica, pesticides were mainly transferred between xylem and cambium, when pesticide was transmitted into the smaller branches, the pith of tree also became the main area of translocation. In the apple tree, translocation was mainly in the late autumn xylem and cambium of the trunk, while in branches pesticides were mainly in the xylem, but distribution area had extended obviously.When Omethoate and dichlorvos were injected into the trunks of three species, they were transferred upward and downward following the sapwood, omethoate appeared obviously in unilateral lines in all three species, only dichlorvos in Mpumilla demonstrated this phenomenon.Experiments showed that the ratio of pesticide and water could objectively reflect plant ability to absorb solvent, the higher ratio, the more absorption.The plant ability to absorb dichlorvos and omethoate were: P. alba var bolleana>M. pumilla>S. japonica. On sunny days, the absorption abilities ofapple tree and poplar tree were higher than that on cloudy day, but for sophora tree this was opposite. We found there existed a great difference in absorption to 30% diohlorvos and omethoate diluted 5 times among eleven woody plants, the rank of absorption from higher to lower were Cratagus pinnatiftda, Pruns persica. M. Pumila, Platycladus orientalis, Ligustrus lucidum,Diospyros kaki, Aesculus chinensis, S. Japonica, Paulownia spp., Populus spp. and Juglans regia.Distribution of pesticides was studied by the Isotope Tracing technique using ?C-radiolabeled omethoate in three woody plants, the detection method and the apparatus were reliable and sensitive. The isotope trace showed that 揅 was distributed obviously more in the canopy, the radioactivity was higher in the first 2m height of trunk than backbone for poplar. In sophora tree, 揅 was distributed more in the xylem and treetop of lower trunk, but ?C was detected more in the upper trunk of apple tree.Residues of omethoate was higher than that of dochlorvos in M. pumi(a leaves, but dichlorvos was higher in the branches and roots, omethoate distributed more in xylem than phloem, dichlorvos residue was mainly in phloem. The residues of omethoate were higher than dichlorvos in all of the S. japonica tissues. The residues of omethoate were more than those of dichlorvos in the leaves of apple tree, dichlorvos was found more in branch and xylem tissues, dichlorvos was not detected in fruit while omethoate was detected a little, the residues of two pesticides we...