3.2 Dynamic distribution, translocation and accumulation of
pesticides in cucumber plants
The
dynamic distribution and accumulation of CLO, DFN and DFZ in cucumber
plants are shown in Fig. 2A under hydroponic experiments. For
CLO and DFN, the concentrations of pesticides in leaves were much higher
than those in roots and stems, indicating that CLO and DFN were mainly
accumulated in leaves, and these have great upward conductivity,
respectively. For DFZ, the concentration of pesticide in roots was much
higher than that in stems and leaves, indicating that DFZ could be
mainly accumulated in roots, and its upward conductivity was poor.
The effects of exogenous SA on the
distribution of three pesticides in the roots, stems and leaves of
cucumber plants are shown in Fig. 2 B, C, D . From the
charts, it can be seen that with SA supplementation the
concentrations of three pesticides in roots, stems and leaves of
cucumber plants basically showed a decreasing trend during the 28 days
of growth. To assess the overall effects of SA on the distribution of
three pesticides in different parts of cucumber plants, the mean
residues of three pesticides in different parts of cucumber plants after
28 days of growth were calculated, respectively (Fig. 3 ).
With SA supplementation at 1mg
L-1, the concentration of CLO and DFN in roots and
leaves significantly decreased by 27%, 18% and 23%, 19%,
respectively, compared with the treatments of CLO and DFN alone; with SA
supplementation at 10mg L-1, the concentration of CLO
and DFN in roots and leaves significantly decreased by 56%, 28% and
46%, 25%, respectively, compared with the treatments of CLO and DFN
alone. With SA supplementation at 50mg L-1, the
concentration of CLO in roots and leaves significantly decreased by 23%
and 20%, respectively, compared with the treatment of CLO alone. For
DFZ, the concentration in roots significantly decreased by 11% and 40%
after addition of SA at 1mg L-1 and 10mg
L-1, respectively, compared with the treatment of DFZ
alone.