THE UPTAKE OF AND STRUCTURAL-CHANGES INDUCED BY TRICHLOROACETIC-ACID IN THE NEEDLES OF SCOTS PINE-SEEDLINGS

The uptake of trichloroacetic acid (TCA) and structural changes induce d in the needles of Scots pine (Pinus sylvestris L.) seedlings were st udied. Two exposure set-ups, a root route and an atmospheric route thr ough the surfaces simulating the wet deposition of fog, were used, Bot h set-ups included two dose levels and corresponding control treatment s. The temperature and the relative humidity in the climate chambers w ere adjusted to represent the conditions of June-July in a subarctic a rea in central Finland. The seedlings were exposed three times a week for two months. The results showed that the uptake of TCA in needles o ccurred both via roots and via needle surface, However, most of the TC A via the atmospheric route was absorbed on the surface of the needles . The structural responses in pine needles depended partly on the trea tment method: TCA applied via the atmospheric route disintegrated the structures of the epicuticular waxes and that of the stomatal cells, w hich was not seen in the exposures via roots. A common feature was the decrease in size of the chloroplasts in concert with the increasing T CA concentrations inside the needles.