Effect of pentachlorophenate, chlorpyrifos and lead chloride on chlorophyll fluorescence

Abstract

Chlorophyll fluorescence parameters were measured in leaves of six plant species (barley, soybean, clover, Tradescantia, Atriplex semibacata and Atriplex patula). Plant cuttings were exposed for 24 hours to lead chloride, sodium pentachlorophenate, butadiene monoxide, ß‐naphthylamine or Ortbo, a commercial brand of insecticide with chlorpyrifos as an active ingredient, at 3–10 different concentrations. Barley and clover were found to be the most responsive species. Sodium pentachlorophenate was the most toxic chemical, followed by lead chloride and Ortho. ß‐naphthylamine and butadiene monoxide were shown to be less harmful. The most reliable parameters in terms of predicting the effect of tested chemical on fluorescence are Fv/Fm, the ratio of variable fluorescence (Fv) to maximal fluorescence (Fm), Fo, initial fluorescence and t_1/2, half the length of time of the rise from minimal to maximal fluorescence. This conclusion is based on the calculation of the coefficients of determination of regression for all parameters.

In the presence of tested chemicals Fo increased, while Fv/Fm and t_1/2 decreased with increasing concentration. Decline of the Fv/Fm indicates the disturbance in the functioning of the photosynthetic electron transport. The increase in Fo suggests the inhibition of PS II reaction center and decrease in t_1/2 is linked to the lowering of the relative number of active PS II centers.

Notes

Present address: Washington University School of Medicine, Department of Pediatrics, St. Louis, MO 63110.