Dissipation and Enantioselective
Degradation of Plant
Growth Retardants Paclobutrazol and Uniconazole in Open Field, Greenhouse,
and Laboratory Soils
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Abstract
Greenhouses are increasingly important in human food
supply. Pesticides
used in greenhouses play important roles in horticulture; however,
little is known about their behavior in greenhouse environments. This
work investigates the dissipation and enantioselctive degradation
of plant growth retardants including paclobutrazol and uniconazole
in soils under three conditions (i.e., open field, greenhouse, and
laboratory). The dissipation and enantioselective degradation of paclobutrazol
and uniconazole in greenhouse were different from those in open field;
they were more persistent in greenhouse than in open field soil. Leaching
produced by rainfall is responsible for the difference in dissipation.
Thus, local environmental impacts may occur more easily inside greenhouses,
while groundwater may be more contaminated in open field. Spike concentrations
of 5, 10, and 20 times the concentrations of native residues were
tested for the enantioselective dissipation of the two pesticides;
the most potent enantioselective degradation of paclobutrazol and
uniconazole occurred at the 10 times that of the native residues in
the greenhouse environments and at 20 times native residues in open
field environments. The higher soil activity in greenhouses than in
open fields was thought to be responsible for such a difference. The
environmental risk and regulation of paclobutrazol and uniconazole
should be considered at the enantiomeric level