Abstract
For plants, light is an indispensable resource. However, it also causes a loss of photosynthetic activity associated with photoinactivation of photosystem II (PSII). In studies of the mechanism of this photoinactivation, there are two conflicting hypotheses at present. One is that excess energy received by leaves, being neither utilized by photosynthesis nor dissipated safely in non-photochemical quenching, causes the photoinactivation. The other involves a two-step mechanism in which excitation of Mn by photons is the primary cause. In the former hypothesis, photoinactivation of PSII should not occur in low light that provides little excess energy, but in the latter hypothesis it should. Therefore, we tested these two hypotheses in different irradiances. We used a system that can measure the fraction of functional PSII complexes under natural conditions and over a long period in intact leaves, which were attached to a plant treated with lincomycin taken up via the roots. The leaves were photoinactivated in low, medium or high light (30, 60 or 950 micromol m(-2) s(-1)) with white, blue, green or red light-emitting diode arrays. Our results showed that the extent of photoinactivation per photon exposure was higher in high light than in low light, consistent with the abundance of excess energy. However, photoinactivation did occur in low light with little excess energy, and blue light caused the greatest extent of photoinactivation followed by white, green and red light in this order, an order that can be predicted from the Mn absorbance spectrum. These results suggest that both mechanisms occur in the photoinactivation process.
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Claims 4
Claim · model-written summary
Photoinactivation per photon exposure was higher in high than low light.
- Taxon
- Capsicum annuum L.
Capsicum annuumt0 - Treatment
- high lighte0
- Outcome
- extent of photoinactivation per photon exposuree0
- Direction
- highere0
- Comparator
- low lighte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Capsicum annuum L. Plants”
e0“the extent of photoinactivation per photon exposure was higher in high light than in low light”
Claim · model-written summary
Photosystem II photoinactivation occurred in low light with little excess energy.
- Taxon
- Capsicum annuum L.Capsicum annuumt0
- Outcome
- photoinactivation did occure0
- Qualifier
- low light with little excess energye0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Capsicum annuum L. Plants”
e0“photoinactivation did occur in low light with little excess energy”
Claim · model-written summary
Blue light caused the greatest photoinactivation, followed by white, green and red light.
- Taxon
- Capsicum annuum L.Capsicum annuumt0
- Treatment
- blue lighte0
- Outcome
- extent of photoinactivatione0
- Direction
- greateste0
- Comparator
- white, green and red lighte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Capsicum annuum L. Plants”
e0“blue light caused the greatest extent of photoinactivation followed by white, green and red light in this order”
Claim · model-written summary
The authors infer that both proposed mechanisms contribute to photoinactivation.
- Taxon
- Capsicum annuum L.Capsicum annuumt0
- Outcome
- photoinactivation processe0
- Qualifier
- both mechanismse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Capsicum annuum L. Plants”
e0“These results suggest that both mechanisms occur in the photoinactivation process.”
The same questions in other papers
light · molecular: metabolites · Capsicum annuum (sweet pepper)Positive and negative results
2 papers in the same direction as this paper · 4 in the opposite direction
- negative
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3 papers more in this group
See all 7 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.