Abstract
Barley (salt-tolerant) and white lupin (salt-sensitive) were grown in sand in pots designed to fit within a pressure chamber. The sand was irrigated with a nutrient solution to which increasing amounts of NaCl were added daily in increments of 10-25 mol m-3. For a range of transpiration rates (Q), the hydrostatic pressure of the leaf xylem sap of an intact plant was measured by applying sufficient air pressure (p) to the root system to raise the pressure of this sap to zero. The relation between p and Q was linear, i.e. of the form p = po + rQ. Po, the intercept on the p axis, reflects the difference in osmotic pressure across the root, and it is assumed that r, the slope of this relation, gives the hydraulic resistance of the plant. In NaCl-treated barley, r remained constant as the NaCl in the soil solution was increased to 200 mol m-3 over 10 days, and differed little from that of the controls. Po increased by about the same amount as the increase in osmotic pressure of the soil solution. This indicates near-perfect osmotic behaviour by the roots, and consistent with this, osmotic pressure of sap expressed from the cut shoot base generally changed little with increasing NaCl, for a given transpiration rate. In NaCl-treated lupin, by contrast, r increased continually from 25 to 150 mol m-3 NaCI, when it was four times that of the controls. Beyond 75 mol m-3, po increased less than increases in the osmotic pressure of the soil solution, which suggests that salts were then leaking into the root xylem. However, the osmotic pressure of the xylem sap flowing through the petiole did not start to increase until 3 days later when the external solution was over 120 mol m-3, suggesting that substantial amounts of NaCl were being removed from the xylem sap before it reached the petiole.
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Claims 6
Claim · model-written summary
In NaCl-treated barley, hydraulic resistance r remained constant as NaCl rose to 200 mol m-3 and differed little from controls.
- Taxon
- barley
.jpg?width=60)
Hordeum vulgaree1 - Treatment
- NaCle1
- Outcome
- hydraulic resistancee2
- Direction
- remained constante1
- Comparator
- controlse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e1“In NaCl-treated barley, r remained constant as the NaCl in the soil solution was increased to 200 mol m-3 over 10 days, and differed little from that of the controls”
e2“it is assumed that r, the slope of this relation, gives the hydraulic resistance of the plant”
Claim · model-written summary
In NaCl-treated barley, Po increased by about the same amount as the increase in osmotic pressure of the soil solution.
- Taxon
- barleyHordeum vulgaree4
- Treatment
- NaCle4
- Outcome
- Poe3
- Direction
- increasede3
- Qualifier
- by about the same amount as the increase in osmotic pressure of the soil solutione3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e4“In NaCl-treated barley”
e3“Po increased by about the same amount as the increase in osmotic pressure of the soil solution”
Claim · model-written summary
In barley, osmotic pressure of sap expressed from the cut shoot base changed little with increasing NaCl at a given transpiration rate.
- Taxon
- barleyHordeum vulgaree4
- Treatment
- increasing NaCle5
- Outcome
- osmotic pressure of sap expressed from the cut shoot basee5
- Direction
- changed littlee5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e4“In NaCl-treated barley”
e5“osmotic pressure of sap expressed from the cut shoot base generally changed little with increasing NaCl, for a given transpiration rate”
Claim · model-written summary
In NaCl-treated lupin, hydraulic resistance r increased continually from 25 to 150 mol m-3 NaCl and was four times that of controls.
- Treatment
- from 25 to 150 mol m-3 NaCIe6
- Outcome
- hydraulic resistancee2
- Direction
- increasede6
- Value
- four timese6
- Qualifier
- continuallye6
- Comparator
- controlse6
LupinusOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e6“In NaCl-treated lupin, by contrast, r increased continually from 25 to 150 mol m-3 NaCI, when it was four times that of the controls”
e2“it is assumed that r, the slope of this relation, gives the hydraulic resistance of the plant”
Claim · model-written summary
In NaCl-treated lupin, Po increased less than the osmotic pressure of the soil solution beyond 75 mol m-3 NaCl.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In NaCl-treated lupin”
e7“Beyond 75 mol m-3, po increased less than increases in the osmotic pressure of the soil solution”
Claim · model-written summary
In lupin, osmotic pressure of the petiole xylem sap did not start to increase until 3 days later, when the external solution was over 120 mol m-3 NaCl.
- Treatment
- over 120 mol m-3e1
- Outcome
- osmotic pressure of the xylem sap flowing through the petiolee1
- Direction
- did not start to increasee1
- Qualifier
- 3 days latere1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In NaCl-treated lupin”
e1“the osmotic pressure of the xylem sap flowing through the petiole did not start to increase until 3 days later when the external solution was over 120 mol m-3”
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