Abstract
BACKGROUND AND AIMS: Certain lines of wild barley (Hordeum spontaneum) are more tolerant of salinity than others. The physiological basis of this difference is examined in a comparative study of a saline-tolerant and saline-intolerant line that emphasizes plant water relations. METHODOLOGY: Effects of salt-treatment (75 mM maximum) extending from a few hours to 3 weeks were quantified in 8-day-old seedlings of a saline-sensitive wild barley line ('T-1') and a less saline-sensitive line ('20-45'). Plants were grown in nutrient culture. Levels of mRNA of the HtPIP2;4 aquaporin (AQP) gene were determined together with a range of physiological responses including root hydraulic conductivity, osmotic potential of root xylem sap, transpiration, leaf relative water content, root water content, leaf water potential, leaf sap osmolality, leaf length, leaf area and chlorophyll content. PRINCIPAL RESULTS: Salt treatment inhibited transpiration and hydraulic conductivity more in salt-tolerant '20-45' plants than in salt-sensitive 'T-1'. In '20-45', the effect was paralleled by a fast (within a few hours) and persistent (3 days) down-regulation of aquaporin. In salt-sensitive 'T-1' plants, aquaporin down-regulation was delayed for up to 24 h. Greater tolerance in '20-45' plants was characterized by less inhibition of leaf area, root fresh weight, leaf water content and chlorophyll concentration. Leaf water potentials were similar in both lines. CONCLUSIONS: (i) Decline in hydraulic conductivity in salt-treated barley plants is important for stomatal closure, (ii) lowered transpiration rate is beneficial for salt tolerance, at least at the seedling stage and (iii) changes in AQP expression are implicated in the control of whole plant hydraulic conductivity and the regulation of shoot water relations.
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Claims 12
Claim · model-written summary
Salt treatment inhibited transpiration more in line 20-45 than T-1.
- Taxon
- wild barley
.jpg?width=60)
Hordeum vulgare subsp. spontaneume1 - Material
- 20-45e0
- Treatment
- Salt treatmente0
- Outcome
- transpiratione0
- Direction
- inhibitede0
- Comparator
- T-1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“Salt treatment inhibited transpiration and hydraulic conductivity more in salt-tolerant '20-45' plants than in salt-sensitive 'T-1'.”
e1“wild barley (Hordeum spontaneum)”
Claim · model-written summary
Salt treatment inhibited hydraulic conductivity more in line 20-45 than T-1.
- Taxon
- wild barleyHordeum vulgare subsp. spontaneume1
- Material
- 20-45e0
- Treatment
- Salt treatmente0
- Outcome
- hydraulic conductivitye0
- Direction
- inhibitede0
- Comparator
- T-1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Salt treatment inhibited transpiration and hydraulic conductivity more in salt-tolerant '20-45' plants than in salt-sensitive 'T-1'.”
e1“wild barley (Hordeum spontaneum)”
Claim · model-written summary
Aquaporin expression in 20-45 was rapidly and persistently downregulated.
- Taxon
- wild barleyHordeum vulgare subsp. spontaneume1
- Material
- 20-45e0
- Gene
- HtPIP2;4e2
- Outcome
- down-regulation of aquaporine0
- Qualifier
- fast (within a few hours) and persistent (3 days)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In '20-45', the effect was paralleled by a fast (within a few hours) and persistent (3 days) down-regulation of aquaporin.”
e1“wild barley (Hordeum spontaneum)”
e2“HtPIP2;4 aquaporin (AQP) gene”
Claim · model-written summary
Aquaporin downregulation in T-1 was delayed up to 24 hours.
- Taxon
- wild barleyHordeum vulgare subsp. spontaneume1
- Material
- T-1e0
- Gene
- HtPIP2;4e2
- Outcome
- aquaporin down-regulatione0
- Direction
- delayede0
- Value
- up to 24 he0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In salt-sensitive 'T-1' plants, aquaporin down-regulation was delayed for up to 24 h.”
e1“wild barley (Hordeum spontaneum)”
e2“HtPIP2;4 aquaporin (AQP) gene”
Claim · model-written summary
Salt-tolerant 20-45 showed less inhibition of leaf area than T-1.
- Taxon
- wild barleyHordeum vulgare subsp. spontaneume1
- Material
- 20-45e0
- Outcome
- leaf areae0
- Direction
- less inhibitione0
- Comparator
- T-1e2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Greater tolerance in '20-45' plants was characterized by less inhibition of leaf area, root fresh weight, leaf water content and chlorophyll concentration.”
e1“wild barley (Hordeum spontaneum)”
e2“In salt-sensitive 'T-1' plants”
Claim · model-written summary
Salt-tolerant 20-45 showed less inhibition of root fresh weight than T-1.
- Taxon
- wild barleyHordeum vulgare subsp. spontaneume1
- Material
- 20-45e0
- Outcome
- root fresh weighte0
- Direction
- less inhibitione0
- Comparator
- T-1e2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Greater tolerance in '20-45' plants was characterized by less inhibition of leaf area, root fresh weight, leaf water content and chlorophyll concentration.”
e1“wild barley (Hordeum spontaneum)”
e2“In salt-sensitive 'T-1' plants”
Claim · model-written summary
Salt-tolerant 20-45 showed less inhibition of leaf water content than T-1.
- Taxon
- wild barleyHordeum vulgare subsp. spontaneume1
- Material
- 20-45e0
- Outcome
- leaf water contente0
- Direction
- less inhibitione0
- Comparator
- T-1e2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Greater tolerance in '20-45' plants was characterized by less inhibition of leaf area, root fresh weight, leaf water content and chlorophyll concentration.”
e1“wild barley (Hordeum spontaneum)”
e2“In salt-sensitive 'T-1' plants”
Claim · model-written summary
Salt-tolerant 20-45 showed less inhibition of chlorophyll concentration than T-1.
- Taxon
- wild barleyHordeum vulgare subsp. spontaneume1
- Material
- 20-45e0
- Outcome
- chlorophyll concentratione0
- Direction
- less inhibitione0
- Comparator
- T-1e2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Greater tolerance in '20-45' plants was characterized by less inhibition of leaf area, root fresh weight, leaf water content and chlorophyll concentration.”
e1“wild barley (Hordeum spontaneum)”
e2“In salt-sensitive 'T-1' plants”
Claim · model-written summary
Leaf water potentials were similar in both lines.
- Taxon
- wild barleyHordeum vulgare subsp. spontaneume1
- Outcome
- Leaf water potentialse0
- Direction
- similare0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaf water potentials were similar in both lines.”
e1“wild barley (Hordeum spontaneum)”
Claim · model-written summary
The authors conclude that declining hydraulic conductivity contributes to stomatal closure under salt treatment.
- Taxon
- barleyHordeum vulgaree0
- Treatment
- salt-treatede0
- Outcome
- stomatal closuree0
- Qualifier
- Decline in hydraulic conductivitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Decline in hydraulic conductivity in salt-treated barley plants is important for stomatal closure”
Claim · model-written summary
The authors conclude that lower transpiration benefits seedling salt tolerance.
- Taxon
- wild barleyHordeum vulgare subsp. spontaneume1
- Organ / stage
- seedling stagee0
- Outcome
- salt tolerancee0
- Qualifier
- lowered transpiration ratee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“lowered transpiration rate is beneficial for salt tolerance, at least at the seedling stage”
e1“wild barley (Hordeum spontaneum)”
Claim · model-written summary
Changes in AQP expression are implicated in controlling plant hydraulic conductivity and shoot water relations.
- Taxon
- wild barleyHordeum vulgare subsp. spontaneume1
- Gene
- AQPe0
- Outcome
- whole plant hydraulic conductivity and the regulation of shoot water relationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“changes in AQP expression are implicated in the control of whole plant hydraulic conductivity and the regulation of shoot water relations”
e1“wild barley (Hordeum spontaneum)”
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