Impairment of photosystem 2 activity at the level of secondary quinone electron acceptor in chloroplasts treated with cobalt, nickel and zinc ions

N. Mohanty, I. Vass, S. Demeter

Research output: Chapter in Book/Report/Conference proceedingChapter

96 Citations (Scopus)

Abstract

The toxicity of heavy metals on photosystem 2 photochemistry, was investigated by monitoring Hill activity, fluorescence, and thermoluminescence properties of photosystem 2 (PS 2) in pea (Pisum sativum L. cv. Bombay) chloroplasts. In Co2+-, Ni2+- or Zn2+-treated chloroplasts 2,6-dichlorophenolindophenol-Hill activity was markedly inhibited. Addition of hydroxylamine which donates electrones close to PS 2 reaction center did not restore the PS 2 activity. Co2+, Ni2+ or Zn2+ also inhibited PS 2 activity supported by hydroxylamine in tris (hydroxymethyl)aminomethane (Tris)-inactivated chloroplasts. These observations were confirmed by fluorescence transient measurements. This implies that the metal ions inhibit either the reaction center or the components of PS 2 acceptor side. Flash-induced thermoluminescence studies revealed that the S2Q(A)- charge recombination was insensitive to metal ion addition. The S2Q(B)- charge recombination, however, was inhibited with increase in the level of Co2+, Ni2+ or Zn2+. The observed sensitivity of S2Q(B)- charge recombination in comparison to the stability of S2Q(A)- recombination suggests that the metal ions inhibit at the level of secondary quinone electron acceptor, Q(B). We suggest that Co2+, Ni2+ or Zn2+ do not block the electron flow between the primary and secondary quinone electron acceptor, but possibly, directly modify Q(B) site, leading to the loss of PS 2 activity.

Original languageEnglish
Title of host publicationPHYSIOL. PLANT.
Pages386-390
Number of pages5
Volume76
Edition3 I
Publication statusPublished - 1989

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Chloroplasts
Cobalt
Nickel
Genetic Recombination
Zinc
Electrons
Ions
Hydroxylamine
Metals
Peas
Fluorescence
2,6-Dichloroindophenol
Photochemistry
Tromethamine
benzoquinone

ASJC Scopus subject areas

  • Medicine(all)

Cite this

Impairment of photosystem 2 activity at the level of secondary quinone electron acceptor in chloroplasts treated with cobalt, nickel and zinc ions. / Mohanty, N.; Vass, I.; Demeter, S.

PHYSIOL. PLANT.. Vol. 76 3 I. ed. 1989. p. 386-390.

Research output: Chapter in Book/Report/Conference proceedingChapter

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AU - Vass, I.

AU - Demeter, S.

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N2 - The toxicity of heavy metals on photosystem 2 photochemistry, was investigated by monitoring Hill activity, fluorescence, and thermoluminescence properties of photosystem 2 (PS 2) in pea (Pisum sativum L. cv. Bombay) chloroplasts. In Co2+-, Ni2+- or Zn2+-treated chloroplasts 2,6-dichlorophenolindophenol-Hill activity was markedly inhibited. Addition of hydroxylamine which donates electrones close to PS 2 reaction center did not restore the PS 2 activity. Co2+, Ni2+ or Zn2+ also inhibited PS 2 activity supported by hydroxylamine in tris (hydroxymethyl)aminomethane (Tris)-inactivated chloroplasts. These observations were confirmed by fluorescence transient measurements. This implies that the metal ions inhibit either the reaction center or the components of PS 2 acceptor side. Flash-induced thermoluminescence studies revealed that the S2Q(A)- charge recombination was insensitive to metal ion addition. The S2Q(B)- charge recombination, however, was inhibited with increase in the level of Co2+, Ni2+ or Zn2+. The observed sensitivity of S2Q(B)- charge recombination in comparison to the stability of S2Q(A)- recombination suggests that the metal ions inhibit at the level of secondary quinone electron acceptor, Q(B). We suggest that Co2+, Ni2+ or Zn2+ do not block the electron flow between the primary and secondary quinone electron acceptor, but possibly, directly modify Q(B) site, leading to the loss of PS 2 activity.

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