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 Co 2+ ‐, Ni 2+ ‐ or Zn 2+ ‐treated chloroplasts 2,6‐dichlorophenolindophenol‐Hill activity was markedly inhibited. Addition of hydroxylamine which donates electrons close to PS 2 reaction center did not restore the PS 2 activity. Co 2+ ‐, Ni 2+ or Zn 2+ 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 S 2 Q − A charge recombination was insensitive to metal ion addition. The S 2 Q − B charge recombination, however, was inhibited with increase in the level of Co 2+ , Ni 2+ or Zn 2+ . The observed sensitivity of S 2 − B charge recombination in comparison to the stability of S 2 Q − A recombination suggests that the metal ions inhibit at the level of secondary quinone electron acceptor. Q B . We suggest that Co 2+ , Ni 2+ or Zn 2+ 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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Claims 8
Claim · model-written summary
Cobalt, nickel and zinc ions markedly inhibited Hill activity in pea chloroplasts.
- Taxon
- pea
Lathyrus oleraceust0 - Treatment
- Co 2+ ‐, Ni 2+ ‐ or Zn 2+e0
- Outcome
- 2,6‐dichlorophenolindophenol‐Hill activitye0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In Co 2+ ‐, Ni 2+ ‐ or Zn 2+ ‐treated chloroplasts 2,6‐dichlorophenolindophenol‐Hill activity was markedly inhibited.”
t0“in pea ( Pisum sativum L. cv. Bombay) chloroplasts”
Claim · model-written summary
Hydroxylamine addition did not restore photosystem 2 activity.
- Taxon
- peaLathyrus oleraceust0
- Treatment
- Addition of hydroxylaminee0
- Outcome
- PS 2 activitye0
- Direction
- did not restoree0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Addition of hydroxylamine which donates electrons close to PS 2 reaction center did not restore the PS 2 activity.”
t0“in pea ( Pisum sativum L. cv. Bombay) chloroplasts”
Claim · model-written summary
Cobalt, nickel and zinc ions inhibited hydroxylamine-supported photosystem 2 activity in Tris-inactivated chloroplasts.
- Taxon
- peaLathyrus oleraceust0
- Treatment
- Co 2+ ‐, Ni 2+ or Zn 2+e0
- Outcome
- PS 2 activity supported by hydroxylaminee0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Co 2+ ‐, Ni 2+ or Zn 2+ also inhibited PS 2 activity supported by hydroxylamine in tris (hydroxymethyl)aminomethane (Tris)‐inactivated chloroplasts.”
t0“in pea ( Pisum sativum L. cv. Bombay) chloroplasts”
Claim · model-written summary
Fluorescence measurements confirmed the photosystem 2 inhibition.
- Taxon
- peaLathyrus oleraceust0
- Outcome
- fluorescence transient measurementse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“These observations were confirmed by fluorescence transient measurements.”
t0“in pea ( Pisum sativum L. cv. Bombay) chloroplasts”
Claim · model-written summary
S2QA charge recombination was insensitive to metal ion addition.
- Taxon
- peaLathyrus oleraceust0
- Treatment
- metal ion additione0
- Outcome
- S 2 Q − A charge recombinatione0
- Direction
- insensitivee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the S 2 Q − A charge recombination was insensitive to metal ion addition.”
t0“in pea ( Pisum sativum L. cv. Bombay) chloroplasts”
Claim · model-written summary
S2QB charge recombination was increasingly inhibited with higher metal-ion levels.
- Taxon
- peaLathyrus oleraceust0
- Treatment
- Co 2+ , Ni 2+ or Zn 2+e0
- Outcome
- S 2 Q − B charge recombinatione0
- Direction
- inhibitede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The S 2 Q − B charge recombination, however, was inhibited with increase in the level of Co 2+ , Ni 2+ or Zn 2+ .”
t0“in pea ( Pisum sativum L. cv. Bombay) chloroplasts”
Claim · model-written summary
The authors infer inhibition at the secondary quinone electron acceptor.
- Taxon
- peaLathyrus oleraceust0
- Treatment
- metal ionse0
- Outcome
- secondary quinone electron acceptore0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the metal ions inhibit at the level of secondary quinone electron acceptor.”
t0“in pea ( Pisum sativum L. cv. Bombay) chloroplasts”
Claim · model-written summary
The authors suggest metal ions directly modify the QB site and cause loss of photosystem 2 activity.
- Taxon
- peaLathyrus oleraceust0
- Outcome
- loss of PS 2 activitye0
- Qualifier
- Q B sitee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“directly modify Q B site, leading to the loss of PS 2 activity.”
t0“in pea ( Pisum sativum L. cv. Bombay) chloroplasts”
The same questions in other papers
nickel(2+) · molecular: metabolites · Lathyrus oleraceus (pea)Positive and negative results
1 in the opposite direction
- positive
co2 · molecular: metabolites · Lathyrus oleraceus (pea)Positive and negative results
2 papers in the same direction as this paper · 3 in the opposite direction
- positive
- positive
- positive
2 papers more in this group
See all 6 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.