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Fluorescence measurements in June 2004 demonstrated the

reduction of photosystem П activity at high doses of Pb (400 and 1000

mg/kg) which was the most significant in the case of lead nitrate

addition (Fig 2b). The reduction of ratio Fy/ F0 was caused by the

reduced Fv whereas F0 values were only slightly affected by Pb

exposure. We observed also 50% decrease of total chlorophyll content

(a+b) in flag leaves in the case of 1000 mg/kg lead addition in the form

of nitrate.

Pb in soil solution,jjg /i

Fig. 1. Lead content in leaves of v .

Dactylis glomerata

as a {unction of lead

concentration in soil solution.

Irrespective of form of lead addition we found a significant correlation

between lead concentration in soil solution and ratio

F y /F o

(Fig 2c);

50% reduction of this ratio was recorded in the experiments at Pb

concentrations in soil solution about 28-50 pg/1. Poorer correlation was

found between Fy/Fo and Pb content in leaves (Fig 2d), 50% reduction

of fluorescence was observed at the range of Pb content in leaves 20-

2000 mg/ kg dry leaves (in control Pb content in leaves was 10 mg/kg).

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