Long-Term Exposure of Sitka Spruce Seedlings to Trichloroacetic Acid
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Date
2003Author
Cape, Neil
Reeves, Nicholas M
Schroder, Peter
Heal, Mathew R
Metadata
Abstract
Trichloroacetic acid (TCA) has been implicated as an
airborne pollutant responsible for adverse effects on forest
health. There is considerable debate as to whether TCA
observed in trees and forest soils is derived from atmospheric
deposition or from in situ production. This experiment
reports the results from treating 4-year-old Sitka spruce
( Picea sitchensis(Bong.) Carr) plants in a greenhouse over
a growing season with TCA supplied either to the soil or
to the foliage at concentrations of 10 and 100 ng mL-1. Similar
uptake of TCA by needles was observed for both modes
of treatment, with significant accumulation of TCA (300 ng
g-1 dry wt) at the higher concentration. Larger concentrations
in stem tissue were seen for the foliar-applied TCA (280 ng
g-1) than for the soil-applied TCA (70 ng g-1), suggesting
that direct stem uptake may be important. Six months after
treatments stopped, TCA concentrations in the needles
of plants exposed to 100 ng mL-1 TCA were still enhanced,
showing that biological degradation of TCA in needles
was slow over the winter. By contrast, no significant
enhancement of TCA in soil could be detected in the directly
treated soils even during the experiment. The protein
content of needles treated with the higher concentration
of TCA by either route was significantly smaller than for the
controls, but there was no effect of TCA on the conjugation
of 1-chloro-2,4-dinitrobenzene in roots nor on the
conjugation of 1,2-dichloro-4-nitrobenzene in needles.