Abstract
Control of rhizosphere pH and exclusion of Al by the plasma membrane have been hypothesized as possible mechanisms for Al tolerance. To test primarily the rhizosphere pH hypothesis, wheat cultivars (Triticum aestivum L. ;Atlas 66' and ;Scout'), which differ in Al tolerance, were grown in either complete nutrient solution, or 0.6 millimolar CaSO(4), with and without Al at pH 4.50. A microelectrode system was used to simultaneously measure rhizosphere pH, K(+), and H(+) fluxes, and membrane potentials (E(m)) along the root at various distances from the root apex. In complete nutrient solution, the rhizosphere pH associated with mature root cells (measured 10-40 millimeters from the root apex) of Al-tolerant ;Atlas 66' was slightly higher than that of the bulk solution, whereas roots of Al-sensitive ;Scout' caused a very small decrease in the rhizosphere pH. In CaSO(4) solution, no significant differences in rhizosphere pH were found between wheat cultivars, while differential Al tolerance was still observed, indicating that the rhizosphere pH associated with mature root tissue is not directly involved in the mechanism(s) of differential Al tolerance. In Al-tolerant ;Atlas 66', growth in a CaSO(4) solution with 5 micromolar Al (pH 4.50) had little effect on net K(+) influx, H(+) efflux, and root-cell membrane potential measured in cells of mature root tissue (from 10-40 mm back from apex). However, in Al-sensitive ;Scout', Al treatment caused a dramatic inhibition of K(+) influx and both a moderate reduction of H(+) efflux and depolarization of the membrane potential. These results demonstrate that increased Al tolerance in wheat is associated with the increased ability of the tolerant plant to maintain normal ion fluxes and membrane potentials across the plasmalemma of root cells in the presence of Al.
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Claims 9
Claim · model-written summary
In complete nutrient solution, rhizosphere pH around mature root cells of the Al-tolerant wheat cultivar Atlas 66 was slightly higher than in the bulk solution.
- Taxon
- wheat
Triticum aestivume1 - Material
- Atlas 66e2
- Organ / stage
- mature root cellse2
- Outcome
- rhizosphere pHe2
- Direction
- slightly highere2
- Comparator
- bulk solutione2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“wheat cultivars (Triticum aestivum L. ;Atlas 66' and ;Scout')”
e2“the rhizosphere pH associated with mature root cells (measured 10-40 millimeters from the root apex) of Al-tolerant ;Atlas 66' was slightly higher than that of the bulk solution”
Claim · model-written summary
Roots of the Al-sensitive wheat cultivar Scout caused a very small decrease in rhizosphere pH in complete nutrient solution.
- Taxon
- wheatTriticum aestivume1
- Material
- Scoute2
- Organ / stage
- rootse2
- Outcome
- rhizosphere pHe2
- Direction
- decreasee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“wheat cultivars (Triticum aestivum L. ;Atlas 66' and ;Scout')”
e2“roots of Al-sensitive ;Scout' caused a very small decrease in the rhizosphere pH”
Claim · model-written summary
In CaSO4 solution, rhizosphere pH did not differ significantly between the wheat cultivars.
- Taxon
- wheatTriticum aestivume2
- Outcome
- rhizosphere pHe2
- Direction
- no significant differencese2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“wheat cultivars (Triticum aestivum L. ;Atlas 66' and ;Scout')”
e2“In CaSO(4) solution, no significant differences in rhizosphere pH were found between wheat cultivars”
Claim · model-written summary
Rhizosphere pH of mature root tissue is not directly involved in the mechanism of differential Al tolerance in wheat.
- Taxon
- wheatTriticum aestivume1
- Organ / stage
- mature root tissuee2
- Outcome
- mechanism(s) of differential Al tolerancee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In CaSO(4) solution, no significant differences in rhizosphere pH were found between wheat cultivars”
e2“indicating that the rhizosphere pH associated with mature root tissue is not directly involved in the mechanism(s) of differential Al tolerance”
Claim · model-written summary
In Al-tolerant Atlas 66 grown with 5 micromolar Al, net K(+) influx, H(+) efflux and root-cell membrane potential in mature root tissue showed little change relative to the solution without Al.
- Taxon
- wheatTriticum aestivume1
- Material
- Atlas 66e2
- Organ / stage
- mature root tissuee2
- Treatment
- 5 micromolar Ale2
- Outcome
- net K(+) influx, H(+) efflux, and root-cell membrane potentiale2
- Direction
- little effecte2
- Comparator
- without Ale3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“wheat cultivars (Triticum aestivum L. ;Atlas 66' and ;Scout')”
e2“In Al-tolerant ;Atlas 66', growth in a CaSO(4) solution with 5 micromolar Al (pH 4.50) had little effect on net K(+) influx, H(+) efflux, and root-cell membrane potential measured in cells of mature root tissue”
e3“were grown in either complete nutrient solution, or 0.6 millimolar CaSO(4), with and without Al at pH 4.50”
Claim · model-written summary
In Al-sensitive Scout treated with Al, K(+) influx was dramatically inhibited relative to the solution without Al.
- Taxon
- wheatTriticum aestivume1
- Material
- Scoute2
- Treatment
- Al treatmente2
- Outcome
- K(+) influxe2
- Direction
- inhibitione2
- Qualifier
- dramatice2
- Comparator
- without Ale3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“wheat cultivars (Triticum aestivum L. ;Atlas 66' and ;Scout')”
e2“However, in Al-sensitive ;Scout', Al treatment caused a dramatic inhibition of K(+) influx”
e3“were grown in either complete nutrient solution, or 0.6 millimolar CaSO(4), with and without Al at pH 4.50”
Claim · model-written summary
In Al-sensitive Scout treated with Al, H(+) efflux was moderately reduced relative to the solution without Al.
- Taxon
- wheatTriticum aestivume1
- Material
- Scoute2
- Treatment
- Al treatmente2
- Outcome
- H(+) effluxe3
- Direction
- reductione3
- Qualifier
- moderatee3
- Comparator
- without Ale4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“wheat cultivars (Triticum aestivum L. ;Atlas 66' and ;Scout')”
e2“However, in Al-sensitive ;Scout', Al treatment caused a dramatic inhibition of K(+) influx”
e3“both a moderate reduction of H(+) efflux and depolarization of the membrane potential”
e4“were grown in either complete nutrient solution, or 0.6 millimolar CaSO(4), with and without Al at pH 4.50”
Claim · model-written summary
In Al-sensitive Scout treated with Al, the membrane potential of mature root tissue depolarized relative to the solution without Al.
- Taxon
- wheatTriticum aestivume1
- Material
- Scoute2
- Treatment
- Al treatmente2
- Outcome
- membrane potentiale3
- Direction
- depolarizatione3
- Comparator
- without Ale4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“wheat cultivars (Triticum aestivum L. ;Atlas 66' and ;Scout')”
e2“However, in Al-sensitive ;Scout', Al treatment caused a dramatic inhibition of K(+) influx”
e3“both a moderate reduction of H(+) efflux and depolarization of the membrane potential”
e4“were grown in either complete nutrient solution, or 0.6 millimolar CaSO(4), with and without Al at pH 4.50”
Claim · model-written summary
Increased Al tolerance in wheat is associated with a greater ability of the tolerant plant to maintain normal ion fluxes and membrane potentials in root cells in the presence of Al.
- Taxon
- wheatTriticum aestivume1
- Organ / stage
- root cellse1
- Outcome
- ion fluxes and membrane potentialse1
- Direction
- increasede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“These results demonstrate that increased Al tolerance in wheat is associated with the increased ability of the tolerant plant to maintain normal ion fluxes and membrane potentials across the plasmalemma of root cells in the presence of Al”