Abstract
Al-induced release of Al-chelating ligands (primarily organic acids) into the rhizosphere from the root apex has been identified as a major Al tolerance mechanism in a number of plant species. In the present study, we conducted physiological investigations to study the spatial and temporal characteristics of Al-activated root organic acid exudation, as well as changes in root organic acid content and Al accumulation, in an Al-tolerant maize (Zea mays) single cross (SLP 181/71 x Cateto Colombia 96/71). These investigations were integrated with biophysical studies using the patch-clamp technique to examine Al-activated anion channel activity in protoplasts isolated from different regions of the maize root. Exposure to Al nearly instantaneously activated a concentration-dependent citrate release, which saturated at rates close to 0.5 nmol citrate h(-1) root(-1), with the half-maximal rates of citrate release occurring at about 20 microM Al(3+) activity. Comparison of citrate exudation rates between decapped and capped roots indicated the root cap does not play a major role in perceiving the Al signal or in the exudation process. Spatial analysis indicated that the predominant citrate exudation is not confined to the root apex, but could be found as far as 5 cm beyond the root cap, involving cortex and stelar cells. Patch clamp recordings obtained in whole-cell and outside-out patches confirmed the presence of an Al-inducible plasma membrane anion channel in protoplasts isolated from stelar or cortical tissues. The unitary conductance of this channel was 23 to 55 pS. Our results suggest that this transporter mediates the Al-induced citrate release observed in the intact tissue. In addition to the rapid Al activation of citrate release, a slower, Al-inducible increase in root citrate content was also observed. These findings led us to speculate that in addition to the Al exclusion mechanism based on root citrate exudation, a second internal Al tolerance mechanism may be operating based on Al-inducible changes in organic acid synthesis and compartmentation. We discuss our findings in terms of recent genetic studies of Al tolerance in maize, which suggest that Al tolerance in maize is a complex trait.
Abstract from the paper’s OpenAlex record, shown for indexing and research. Copyright remains with the authors or the publisher. Read at the source ↗
The text the model read, with the source record’s inline markup (italics, sub- and superscripts) rendered and its character entities decoded; quote offsets refer to the raw text.
Claims 9
Claim · model-written summary
Al exposure rapidly activated concentration-dependent citrate release from maize roots, saturating near 0.5 nmol citrate h(-1) root(-1).
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Exposure to Al nearly instantaneously activated a concentration-dependent citrate release, which saturated at rates close to 0.5 nmol citrate h(-1) root(-1)”
t0“Maize”
Claim · model-written summary
Half-maximal maize root citrate release occurred near 20 microM Al(3+) activity.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“half-maximal rates of citrate release occurring at about 20 microM Al(3+) activity”
t0“Maize”
Claim · model-written summary
Decapping roots suggested the root cap has no major role in Al signal perception or citrate exudation.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Comparison of citrate exudation rates between decapped and capped roots indicated the root cap does not play a major role in perceiving the Al signal or in the exudation process”
t0“Maize”
Claim · model-written summary
Citrate exudation extended as far as 5 cm beyond the maize root cap and involved cortex and stelar cells.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“predominant citrate exudation is not confined to the root apex, but could be found as far as 5 cm beyond the root cap, involving cortex and stelar cells”
t0“Maize”
Claim · model-written summary
An Al-inducible plasma membrane anion channel was found in maize stelar and cortical protoplasts.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“presence of an Al-inducible plasma membrane anion channel in protoplasts isolated from stelar or cortical tissues”
t0“Maize”
Claim · model-written summary
The maize anion channel had unitary conductance of 23 to 55 pS.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The unitary conductance of this channel was 23 to 55 pS”
t0“Maize”
Claim · model-written summary
The authors suggest the anion channel mediates Al-induced citrate release.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this transporter mediates the Al-induced citrate release observed in the intact tissue”
t0“Maize”
Claim · model-written summary
Al induced a slower increase in maize root citrate content.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a slower, Al-inducible increase in root citrate content was also observed”
t0“Maize”
Claim · model-written summary
The authors speculate that changes in organic acid synthesis and compartmentation may provide a second internal Al tolerance mechanism.
- Outcome
- internal Al tolerance mechanisme0
- Qualifier
- Al-inducible changes in organic acid synthesis and compartmentatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a second internal Al tolerance mechanism may be operating based on Al-inducible changes in organic acid synthesis and compartmentation”
t0“Maize”
The same questions in other papers
aluminium atom · molecular: metabolites · Zea mays (maize)Positive and negative results
7 papers in the same direction as this paper · 18 in the opposite direction
- negative
- negative
- positive
22 papers more in this group
See all 26 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.