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KMID : 0368419820250010021
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Journal of Plant Biology
1982 Volume.25 No. 1 p.21 ~ p.36
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Protective Effects of Phosphate and ATP Pretreatment on Pb-Inhibiting Photosystem Ⅱ Activity
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Sung Min-Wung
Kwon Byung-Kyu
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Abstract
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The activity of photosystem Ⅱ in isolated chloroplast from the leaves of Sedum sarmentosum was measured. The photoreduction rate of DCPIP by photosystem Ⅱ showed the circadian rhythm with a peak at near midday sample for a continuing fine day and at near afternoon between midday and sunset sample for a continuing cloudy day in summer. The optimum light intensity of photoreduction by phtosystem Ⅱ in the chloroplast preparation was about 5∼9×10^4 lux. The saturated light intensity was over 9×10^4 lux. Photosystem Ⅱ activity was inhibited by even the lowest concentration of lead. When Pi and ATP of the same concentration as Pb were added to the reaction mixture containing Tris buffer lacking of Pi prior to Pb incuvation, photosystem Ⅱ activity was protected from Pb-inhibiting effect by the the pretreatment of Pi and ATP. It was assumed that Pb inhibition was probably due to one, P-depriveing by the precipitates of Pb_3 (PO_4)_2 in the reaction mixture and the other, partially Pb-combing with Pi groups of the active site of photosystem Ⅱ.
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