Abstract
*The effects of zinc (Zn) toxicity on photosynthesis and respiration were investigated in sugar beet (Beta vulgaris) plants grown hydroponically with 1.2, 100 and 300 microM Zn. *A photosynthesis limitation analysis was used to assess the stomatal, mesophyll, photochemical and biochemical contributions to the reduced photosynthesis observed under Zn toxicity. *The main limitation to photosynthesis was attributable to stomata, with stomatal conductances decreasing by 76% under Zn excess and stomata being unable to respond to physiological and chemical stimuli. The effects of excess Zn on photochemistry were minor. Scanning electron microscopy showed morphological changes in stomata and mesophyll tissue. Stomatal size and density were smaller, and stomatal slits were sealed in plants grown under high Zn. Moreover, the mesophyll conductance to CO(2) decreased by 48% under Zn excess, despite a marked increase in carbonic anhydrase activity. Respiration, including that through both cytochrome and alternative pathways, was doubled by high Zn. *It can be concluded that, in sugar beet plants grown in the presence of excess Zn, photosynthesis is impaired due to a depletion of CO(2) at the Rubisco carboxylation site, as a consequence of major decreases in stomatal and mesophyll conductances to CO(2).
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Claims 11
Claim · model-written summary
Excess zinc reduced sugar beet photosynthesis.
- Taxon
- sugar beet (Beta vulgaris)
Beta vulgarist0 - Treatment
- Zn toxicitye0
- Outcome
- photosynthesise0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“reduced photosynthesis observed under Zn toxicity”
t0“sugar beet (Beta vulgaris)”
Claim · model-written summary
Stomatal conductance decreased by 76% under excess zinc.
- Taxon
- sugar beet (Beta vulgaris)Beta vulgarist0
- Treatment
- Zn excesse0
- Outcome
- stomatal conductancese0
- Direction
- decreasinge0
- Value
- 76%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“stomatal conductances decreasing by 76% under Zn excess”
t0“sugar beet (Beta vulgaris)”
Claim · model-written summary
Stomata under zinc excess were unable to respond to physiological and chemical stimuli.
- Taxon
- sugar beet (Beta vulgaris)Beta vulgarist0
- Outcome
- stomata being unable to respond to physiological and chemical stimulie0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“stomata being unable to respond to physiological and chemical stimuli.”
t0“sugar beet (Beta vulgaris)”
Claim · model-written summary
Excess zinc had minor effects on photochemistry.
- Taxon
- sugar beet (Beta vulgaris)Beta vulgarist0
- Treatment
- excess Zne0
- Outcome
- photochemistrye0
- Qualifier
- minore0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The effects of excess Zn on photochemistry were minor.”
t0“sugar beet (Beta vulgaris)”
Claim · model-written summary
High zinc reduced stomatal size.
- Taxon
- sugar beet (Beta vulgaris)Beta vulgarist0
- Treatment
- high Zne0
- Outcome
- Stomatal sizee0
- Direction
- smallere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Stomatal size and density were smaller, and stomatal slits were sealed in plants grown under high Zn.”
t0“sugar beet (Beta vulgaris)”
Claim · model-written summary
High zinc reduced stomatal density.
- Taxon
- sugar beet (Beta vulgaris)Beta vulgarist0
- Treatment
- high Zne0
- Outcome
- densitye0
- Direction
- smallere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Stomatal size and density were smaller, and stomatal slits were sealed in plants grown under high Zn.”
t0“sugar beet (Beta vulgaris)”
Claim · model-written summary
Stomatal slits were sealed under high zinc.
- Taxon
- sugar beet (Beta vulgaris)Beta vulgarist0
- Treatment
- high Zne0
- Outcome
- stomatal slits were sealede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“stomatal slits were sealed in plants grown under high Zn.”
t0“sugar beet (Beta vulgaris)”
Claim · model-written summary
Mesophyll conductance to CO(2) fell by 48% under excess zinc.
- Taxon
- sugar beet (Beta vulgaris)Beta vulgarist0
- Treatment
- Zn excesse0
- Outcome
- mesophyll conductance to CO(2)e0
- Direction
- decreasede0
- Value
- 48%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the mesophyll conductance to CO(2) decreased by 48% under Zn excess”
t0“sugar beet (Beta vulgaris)”
Claim · model-written summary
Carbonic anhydrase activity increased markedly under zinc excess.
- Taxon
- sugar beet (Beta vulgaris)Beta vulgarist0
- Treatment
- Zn excesse1
- Gene
- carbonic anhydrasee0
- Outcome
- carbonic anhydrase activitye0
- Direction
- marked increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“despite a marked increase in carbonic anhydrase activity.”
e1“mesophyll conductance to CO(2) decreased by 48% under Zn excess”
t0“sugar beet (Beta vulgaris)”
Claim · model-written summary
High zinc doubled respiration through cytochrome and alternative pathways.
- Taxon
- sugar beet (Beta vulgaris)Beta vulgarist0
- Treatment
- high Zne0
- Outcome
- Respiration, including that through both cytochrome and alternative pathwayse0
- Direction
- doublede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Respiration, including that through both cytochrome and alternative pathways, was doubled by high Zn.”
t0“sugar beet (Beta vulgaris)”
Claim · model-written summary
The authors attribute impaired photosynthesis under excess zinc to CO(2) depletion at Rubisco due to stomatal and mesophyll conductance loss.
- Taxon
- sugar beet (Beta vulgaris)Beta vulgarist0
- Outcome
- photosynthesis is impairede0
- Qualifier
- depletion of CO(2) at the Rubisco carboxylation sitee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“photosynthesis is impaired due to a depletion of CO(2) at the Rubisco carboxylation site, as a consequence of major decreases in stomatal and mesophyll conductances to CO(2).”
t0“sugar beet (Beta vulgaris)”
The same questions in other papers
zinc atom · growth · Beta vulgaris (beet)Positive and negative results
4 papers in the same direction as this paper · 13 in the opposite direction
- negative
- positive
- positive
14 papers more in this group
See all 18 papers →zinc atom · physiology: photosynthesis · Beta vulgaris (beet)Results agree
1 paper in the same direction as this paper
- negative
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.