EFFECT OF PENTACHLOROPHENATE, CHLORPYRIFOS AND LEAD CHLORIDE ON CHLOROPHYLL FLUORESCENCE

Chlorophyll fluorescence parameters were measured in leaves of six pla nt species (barley, soybean, clover, Tradescantia, Atriplex semibacata and Atriplex patula). Plant cuttings were exposed for 24 hours to lea d chloride, sodium pentachlorophenate, butadiene monoxide, beta-naphth ylamine or Ortho, a commercial brand of insecticide with chlorpyrifos as an active ingredient, at 3-10 different concentrations. Parley and clover were found to be the most responsive species. Sodium pentachlor ophenate was the most toxic chemical, followed by lead chloride and Or tho. beta-naphthylamine and butadiene monoxide were shown to be less h armful. The most reliable parameters in terms of predicting the effect of tested chemical on fluorescence are Fv/Fm, the ratio of variable f luorescence (Fv) to maximal fluorescence (Fm), Fo, initial fluorescenc e and t(1/2), half the length of time of the rise from minimal to maxi mal fluorescence. This conclusion is based on the calculation of the c oefficients of determination of regression for all parameters. In the presence of tested chemicals Fcr increased, while Fv/Fm and t(1/2) dec reased with increasing concentration. Decline of the Fv/Fm indicates t he disturbance in the functioning of the photosynthetic electron trans port. The increase in Fo suggests the inhibition oi PS II reaction cen ter and decrease in t(1/2) is linked to the towering of the relative n umber of active PS II centers.