DETERMINATION OF PHYTOTOXICITY OF SEVERAL VOLATILE ORGANIC-COMPOUNDS BY INVESTIGATING THE GERMINATION PATTERN OF TOBACCO POLLEN

Hydrated pollen of Nicotiana tabacum L. (var. xanthi nc) was exposed to different concentrations of several volatile organic compounds. The germination rate of the pollen was determined by applying a modified test procedure originally developed by Kappler and Kristen (1990). A stimulation of pollen germination resulting through a rise in pCO(2) was avoided by using a short exposure period. In the series of chlorinated ethanes, the ED(50) (and ED(25)) values decrease with increasing number of chlorine atoms, which are correlated to a rise of the octanol-water partition coefficient. For the chlorinated ethenes a similar effect is probable, but less obvious. The toxicity of compounds with the same number of chlorine atoms is higher for ethane derivatives than for derivatives of ethene. The ED(50) and ED(25) values are compared with threshold values of physiological effects obtained after the application of 1,1,1-trichloroethane for 24 h to tobacco leaves. We presume that chlorinated hydrocarbons may cause stress even at lower concentrations than those suggested by the pollen test. Therefore the listed ED values (Table 1) should be considered as maximum tolerable values regarding phytotoxic effects in experimental investigations. For the important solvent 1,1,1-trichloroethane the ED(25) value of phytotoxicity is lower than 4 mg/L; according to literature the concentration supposedly having no effect on man is 1.9-5.2 mg/L.