Abstract
Drought induces stomatal closure, a response that is associated with the activation of plasma membrane anion channels in guard cells, by the phytohormone abscisic acid (ABA). In several species, this response is associated with changes in the cytoplasmic free Ca(2+) concentration. In Vicia faba, however, guard cell anion channels activate in a Ca(2+)-independent manner. Because of potential differences between species, Nicotiana tabacum guard cells were studied in intact plants, with simultaneous recordings of the plasma membrane conductance and the cytoplasmic free Ca(2+) concentration. ABA triggered transient rises in cytoplasmic Ca(2+) in the majority of the guard cells (14 out of 19). In seven out of 14 guard cells, the change in cytoplasmic free Ca(2+) closely matched the activation of anion channels, while the Ca(2+) rise was delayed in seven other cells. In the remaining five cells, ABA stimulated anion channels without a change in the cytoplasmic Ca(2+) level. Even though ABA could activate anion channels in N. tabacum guard cells independent of a rise in the cytoplasmic Ca(2+) concentration, patch clamp experiments showed that anion channels in these cells are stimulated by elevated Ca(2+) in an ATP-dependent manner. Guard cells thus seem to have evolved both Ca(2+)-independent and -dependent ABA signaling pathways. Guard cells of N. tabacum apparently utilize both pathways, while ABA signaling in V. faba seems to be restricted to the Ca(2+)-independent pathway.
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Claims 6
Claim · model-written summary
ABA caused transient cytoplasmic calcium rises in 14 of 19 guard cells.
- Taxon
- Nicotiana tabacum
Nicotiana tabacumt0 - Organ / stage
- guard cellse0
- Treatment
- ABAe0
- Outcome
- transient rises in cytoplasmic Ca(2+)e0
- Direction
- risese0
- Value
- 14 out of 19e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nicotiana tabacum”
e0“ABA triggered transient rises in cytoplasmic Ca(2+) in the majority of the guard cells (14 out of 19)”
Claim · model-written summary
In seven of 14 guard cells, the calcium change closely matched anion-channel activation.
- Taxon
- Nicotiana tabacumNicotiana tabacumt0
- Organ / stage
- guard cellse0
- Compound
- Ca(2+)e0
- Outcome
- activation of anion channelse0
- Qualifier
- seven out of 14 guard cellse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nicotiana tabacum”
e0“In seven out of 14 guard cells, the change in cytoplasmic free Ca(2+) closely matched the activation of anion channels”
Claim · model-written summary
In seven other cells, the calcium rise was delayed.
- Taxon
- Nicotiana tabacumNicotiana tabacumt0
- Outcome
- Ca(2+) risee0
- Direction
- delayede0
- Qualifier
- seven other cellse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nicotiana tabacum”
e0“the Ca(2+) rise was delayed in seven other cells”
Claim · model-written summary
ABA stimulated anion channels without a cytoplasmic calcium change in five cells.
- Taxon
- Nicotiana tabacumNicotiana tabacumt0
- Treatment
- ABAe0
- Outcome
- anion channelse0
- Direction
- stimulatede0
- Qualifier
- without a change in the cytoplasmic Ca(2+) levele0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nicotiana tabacum”
e0“In the remaining five cells, ABA stimulated anion channels without a change in the cytoplasmic Ca(2+) level”
Claim · model-written summary
Elevated calcium stimulated anion channels in an ATP-dependent manner.
- Taxon
- Nicotiana tabacumNicotiana tabacumt0
- Treatment
- elevated Ca(2+)e0
- Outcome
- anion channelse0
- Direction
- stimulatede0
- Qualifier
- ATP-dependent mannere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nicotiana tabacum”
e0“anion channels in these cells are stimulated by elevated Ca(2+) in an ATP-dependent manner”
Claim · model-written summary
Tobacco guard cells appear to use both calcium-dependent and independent ABA signalling.
- Taxon
- Nicotiana tabacumNicotiana tabacumt0
- Organ / stage
- Guard cellse0
- Outcome
- both pathwayse0
- Qualifier
- apparentlye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Nicotiana tabacum”
e0“Guard cells of N. tabacum apparently utilize both pathways”
The same questions in other papers
calcium(2+) · molecular: metabolites · Nicotiana tabacum (tobacco)Positive and negative results
1 in the opposite direction
- negative
(+)-abscisic acid · molecular: metabolites · Nicotiana tabacum (tobacco)Positive and negative results
6 papers in the same direction as this paper · 6 in the opposite direction
- no effect
- negative
- no effect
9 papers more in this group
See all 13 papers →(+)-abscisic acid · nutrient: content · Nicotiana tabacum (tobacco)Results agree
2 papers in the same direction as this paper
- positive
- positive
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.