Abstract
The aims of this study were to quantify developmental differences in acid growth along the root axis and to determine whether these differences were due to alterations in cell turgor or cell wall properties. The apoplast pH of maize roots growing in hydroponics was altered from pH 7.0 to pH 3.4 using 2 mol m−3 citrate-phosphate buffer or unbuffered solutions. Whole root elongation rate rapidly increased and measurement of the local growth profile indicated that this increase in growth occurred in young cells in the accelerating zone (apical 0–4 mm) while more proximal growing cells were unaffected. Unbuffered solutions of identical pH produced qualitatively similar results. Single cell turgor pressures were unchanged between pH treatments both longitudinally and radially in the root tip. This suggests that the rapid acid-induced changes in growth rate were due to an increase in cell wall loosening. Single cell osmotic pressure and water potential were not significantly different between pH treatments. Acid pH caused net solute import at the root tip to increase 3- to 4-fold, which, coupled with the maintenance of turgor and osmotic pressure, indicated that solute import was not limiting expansion. Thus, acidic solutions cause an increase in growth in accelerating but not decelerating regions. It has been shown for the first time that acid growth in intact, growing roots is not due to differences in turgor, assigning these changes to cell wall properties. Possible cell wall biochemical alterations are discussed.
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Claims 7
Claim · model-written summary
Acid treatment increased whole maize root elongation, localized to the apical accelerating zone.
- Organ / stage
- accelerating zone (apical 0–4 mm)e0
- Treatment
- pH 3.4e0
- Outcome
- Whole root elongation ratee0
- Direction
- increasede0
- Comparator
- pH 7.0e0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The apoplast pH of maize roots growing in hydroponics was altered from pH 7.0 to pH 3.4 using 2 mol m−3 citrate-phosphate buffer or unbuffered solutions. Whole root elongation rate rapidly increased and measurement of the local growth profile indicated that this increase in growth occurred in young cells in the accelerating zone (apical 0–4 mm) while more proximal growing cells were unaffected”
Claim · model-written summary
More proximal growing maize root cells were unaffected by the acid treatment.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this increase in growth occurred in young cells in the accelerating zone (apical 0–4 mm) while more proximal growing cells were unaffected”
e1“The apoplast pH of maize roots growing in hydroponics was altered from pH 7.0 to pH 3.4 using 2 mol m−3 citrate-phosphate buffer or unbuffered solutions”
t0“root growing zone”
Claim · model-written summary
Unbuffered pH-matched solutions produced qualitatively similar growth responses.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Unbuffered solutions of identical pH produced qualitatively similar results”
e1“The apoplast pH of maize roots growing in hydroponics was altered from pH 7.0 to pH 3.4 using 2 mol m−3 citrate-phosphate buffer or unbuffered solutions”
t0“root growing zone”
Claim · model-written summary
Single-cell turgor pressures did not change between pH treatments.
- Organ / stage
- root tipe0
- Treatment
- pH treatmentse0
- Outcome
- Single cell turgor pressurese0
- Direction
- unchangede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Single cell turgor pressures were unchanged between pH treatments both longitudinally and radially in the root tip”
e1“The apoplast pH of maize roots growing in hydroponics was altered from pH 7.0 to pH 3.4 using 2 mol m−3 citrate-phosphate buffer or unbuffered solutions”
t0“root growing zone”
Claim · model-written summary
Single-cell osmotic pressure and water potential did not significantly differ between pH treatments.
- Treatment
- pH treatmentse0
- Outcome
- Single cell osmotic pressure and water potentiale0
- Direction
- not significantly differente0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Single cell osmotic pressure and water potential were not significantly different between pH treatments”
e1“The apoplast pH of maize roots growing in hydroponics was altered from pH 7.0 to pH 3.4 using 2 mol m−3 citrate-phosphate buffer or unbuffered solutions”
t0“root growing zone”
Claim · model-written summary
Acid pH increased net solute import at the root tip three- to fourfold.
- Organ / stage
- root tipe0
- Treatment
- Acid pHe0
- Outcome
- net solute importe0
- Direction
- increasee0
- Value
- 3- to 4-folde0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Acid pH caused net solute import at the root tip to increase 3- to 4-fold”
e1“The apoplast pH of maize roots growing in hydroponics was altered from pH 7.0 to pH 3.4 using 2 mol m−3 citrate-phosphate buffer or unbuffered solutions”
t0“root growing zone”
Claim · model-written summary
Acid-induced growth change was attributed to increased cell wall loosening rather than turgor.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This suggests that the rapid acid-induced changes in growth rate were due to an increase in cell wall loosening”
e1“The apoplast pH of maize roots growing in hydroponics was altered from pH 7.0 to pH 3.4 using 2 mol m−3 citrate-phosphate buffer or unbuffered solutions”
t0“root growing zone”
The same questions in other papers
ph · growth · Zea mays (maize)Results differ
18 papers in the same direction as this paper · 22 in the opposite direction · 2 reporting no difference from an alternative
- negative
- negative
- negative
39 papers more in this group
See all 43 papers →ph · physiology: water · Zea mays (maize)Positive and negative results
2 papers in the same direction as this paper · 1 in the opposite direction
- positive
- negative
- 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.