LONG-TERM EXPOSURE OF SCOTS PINE-SEEDLINGS TO MONOCHLOROACETIC AND TRICHLOROACETIC-ACID - EFFECTS ON THE NEEDLES AND GROWTH

The effects of monochloroacetic acid (MCA) and trichloroacetic acid (T CA) exposures on Scots pine seedlings were studied. The exposures, wit h two dose levels for TCA and one for MCA, were done simultaneously vi a the roots and the foliage during two consecutive simulated growing s easons. An increase in potassium concentration in current-year needles exposed to lower TCA dose after the first exposure season, and an inc rease in the nitrogen concentration, as well as a decrease in the tran spiration rate and in the total chloroplast area, were noted in the cu rrent-year needles exposed to MCA after the second exposure season and these changes were statistically different from the control. These re sults may be due to charge compensation and hormonal changes induced b y subtoxic levels of TCA and MCA.