Abstract
Different aspects of salt excretion from leaves of the xero‐halophyte Reaumuria hirtella Jaub. et Sp. (Tamaricaceae) were investigated under the extremely arid conditions of the desert. The diurnal excretion pattern, which gradually decreased toward midday, showed a negative correlation with the daily transpiration pattern. The relative excretion, which is the ratio between the absolute excretion of Na + and the change in its internal content, was maximal at sites with low salinity, and decreased when the concentration of NaCl in the root environment increased. By contrast, the absolute excretion increased from 253 to 323 m mol Na + g −1 f. wt per 12 h with increase in the total soil salinity from 0·24 to 1·23%, respectively. Water stress conditions, caused either by increasing soil salinity or by dryness of the atmosphere, greatly influenced the efficiency of excretion process. Six ions: Na + , K + , Ca 2+ , Mg 2+ , Cl − and SO 4 2− constituted 96·8% of the d. wt of the field‐collected secreted salts. Na + and Cl − , which were the predominating ions in the soil solution of the root environment, were also the predominantly secreted, constituting c . 89% of salts secreted. The proportion of Na + which was prevented from entry into the roots increased with increasing Na + concentration in the soil solution. More than 67% of the absorbed NaCl was secreted by leaves during the day. However, the accumulated salts contributed to the osmotic potential (ψ s ) and improved the plant water status. The osmotic potential of the plant sap at the end of the day or during periods of low excretion rates was shown to be decreased −7·3 to −13·7 bar from that in the morning. The fraction of osmotic potential decreased during the day (Δψ s ) was positively correlated with the soil salinity. These retained salts are expelled from the leaves by increased efficiency of extraction during the night and early morning, so that the plant begins the day with low internal salt content, and the leaf reservoirs become suitable for a new supply. The rejection mechanism at the plant roots and the secretion mechanism at shoots allow the plant to maintain its internal salt content at an approximately constant level despite the great variation in soil salinity.
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Claims 13
Claim · model-written summary
Diurnal salt excretion decreased toward midday and was negatively correlated with daily transpiration.
- Taxon
- Reaumuria hirtella
Reaumuria hirtellae0 - Outcome
- diurnal excretion patterne1
- Direction
- decreasede1
- Comparator
- daily transpiration patterne1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Reaumuria hirtella Jaub. et Sp. (Tamaricaceae) were investigated under the extremely arid conditions of the desert”
e1“The diurnal excretion pattern, which gradually decreased toward midday, showed a negative correlation with the daily transpiration pattern”
Claim · model-written summary
Relative salt excretion was maximal at low salinity and decreased as NaCl concentration in the root environment increased.
- Taxon
- Reaumuria hirtellaReaumuria hirtellae0
- Treatment
- concentration of NaCl in the root environmente2
- Outcome
- relative excretione2
- Direction
- decreasede2
- Comparator
- low salinitye2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Reaumuria hirtella Jaub. et Sp. (Tamaricaceae) were investigated under the extremely arid conditions of the desert”
e2“The relative excretion, which is the ratio between the absolute excretion of Na + and the change in its internal content, was maximal at sites with low salinity, and decreased when the concentration of NaCl in the root environment increased”
Claim · model-written summary
Absolute salt excretion increased from 253 to 323 m mol Na+ g-1 f. wt per 12 h as total soil salinity rose from 0.24 to 1.23%.
- Taxon
- Reaumuria hirtellaReaumuria hirtellae0
- Treatment
- total soil salinitye3
- Outcome
- absolute excretione3
- Direction
- increasede3
- Value
- 253 to 323 m mol Na + g −1 f. wt per 12 he3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Reaumuria hirtella Jaub. et Sp. (Tamaricaceae) were investigated under the extremely arid conditions of the desert”
e3“the absolute excretion increased from 253 to 323 m mol Na + g −1 f. wt per 12 h with increase in the total soil salinity from 0·24 to 1·23%”
Claim · model-written summary
Water stress from soil salinity or atmospheric dryness greatly influenced the efficiency of salt excretion.
- Taxon
- Reaumuria hirtellaReaumuria hirtellae0
- Treatment
- Water stress conditionse4
- Outcome
- efficiency of excretion processe4
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Reaumuria hirtella Jaub. et Sp. (Tamaricaceae) were investigated under the extremely arid conditions of the desert”
e4“Water stress conditions, caused either by increasing soil salinity or by dryness of the atmosphere, greatly influenced the efficiency of excretion process”
Claim · model-written summary
Six ions constituted 96.8% of the dry weight of the field-collected secreted salts.
- Taxon
- Reaumuria hirtellaReaumuria hirtellae0
- Outcome
- Six ionse5
- Value
- 96·8%e5
- Qualifier
- of the d. wte5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Reaumuria hirtella Jaub. et Sp. (Tamaricaceae) were investigated under the extremely arid conditions of the desert”
e5“Six ions: Na + , K + , Ca 2+ , Mg 2+ , Cl − and SO 4 2− constituted 96·8% of the d. wt”
Claim · model-written summary
Na+ and Cl− were the predominantly secreted salts, constituting c. 89% of secreted salts.
- Taxon
- Reaumuria hirtellaReaumuria hirtellae0
- Outcome
- Na + and Cl −e6
- Value
- c . 89%e6
- Qualifier
- predominantly secretede6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Reaumuria hirtella Jaub. et Sp. (Tamaricaceae) were investigated under the extremely arid conditions of the desert”
e6“Na + and Cl − , which were the predominating ions in the soil solution of the root environment, were also the predominantly secreted, constituting c . 89% of salts secreted”
Claim · model-written summary
The proportion of Na+ kept out of the roots increased with increasing Na+ concentration in the soil solution.
- Taxon
- Reaumuria hirtellaReaumuria hirtellae0
- Treatment
- increasing Na + concentration in the soil solutione7
- Outcome
- proportion of Na + which was prevented from entry into the rootse7
- Direction
- increasede7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Reaumuria hirtella Jaub. et Sp. (Tamaricaceae) were investigated under the extremely arid conditions of the desert”
e7“The proportion of Na + which was prevented from entry into the roots increased with increasing Na + concentration in the soil solution”
Claim · model-written summary
More than 67% of absorbed NaCl was secreted by leaves during the day.
- Taxon
- Reaumuria hirtellaReaumuria hirtellae0
- Organ / stage
- leavese1
- Outcome
- secreted by leaves during the daye1
- Value
- More than 67%e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Reaumuria hirtella Jaub. et Sp. (Tamaricaceae) were investigated under the extremely arid conditions of the desert”
e1“More than 67% of the absorbed NaCl was secreted by leaves during the day”
Claim · model-written summary
Accumulated salts contributed to the osmotic potential and improved the plant water status.
- Taxon
- Reaumuria hirtellaReaumuria hirtellae0
- Compound
- accumulated saltse1
- Outcome
- plant water statuse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Reaumuria hirtella Jaub. et Sp. (Tamaricaceae) were investigated under the extremely arid conditions of the desert”
e1“the accumulated salts contributed to the osmotic potential (ψ s ) and improved the plant water status”
Claim · model-written summary
Plant sap osmotic potential decreased by −7.3 to −13.7 bar during the day relative to the morning.
- Taxon
- Reaumuria hirtellaReaumuria hirtellae0
- Outcome
- osmotic potential of the plant sape1
- Direction
- decreasede1
- Value
- −7·3 to −13·7 bare1
- Comparator
- that in the morninge1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Reaumuria hirtella Jaub. et Sp. (Tamaricaceae) were investigated under the extremely arid conditions of the desert”
e1“The osmotic potential of the plant sap at the end of the day or during periods of low excretion rates was shown to be decreased −7·3 to −13·7 bar from that in the morning”
Claim · model-written summary
The fraction of osmotic potential decreased during the day was positively correlated with soil salinity.
- Taxon
- Reaumuria hirtellaReaumuria hirtellae0
- Treatment
- soil salinitye1
- Outcome
- fraction of osmotic potential decreased during the daye1
- Direction
- increaseinferrede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Reaumuria hirtella Jaub. et Sp. (Tamaricaceae) were investigated under the extremely arid conditions of the desert”
e1“The fraction of osmotic potential decreased during the day (Δψ s ) was positively correlated with the soil salinity”
Claim · model-written summary
Retained salts are expelled by increased extraction efficiency at night and early morning, so the plant starts the day with low internal salt content.
- Taxon
- Reaumuria hirtellaReaumuria hirtellae0
- Outcome
- internal salt contente1
- Qualifier
- increased efficiency of extraction during the night and early morninge1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Reaumuria hirtella Jaub. et Sp. (Tamaricaceae) were investigated under the extremely arid conditions of the desert”
e1“These retained salts are expelled from the leaves by increased efficiency of extraction during the night and early morning, so that the plant begins the day with low internal salt content”
Claim · model-written summary
Rejection at roots and secretion at shoots maintain internal salt content at an approximately constant level despite variation in soil salinity.
- Taxon
- Reaumuria hirtellaReaumuria hirtellae0
- Outcome
- internal salt contente1
- Qualifier
- The rejection mechanism at the plant roots and the secretion mechanism at shootse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Reaumuria hirtella Jaub. et Sp. (Tamaricaceae) were investigated under the extremely arid conditions of the desert”
e1“The rejection mechanism at the plant roots and the secretion mechanism at shoots allow the plant to maintain its internal salt content at an approximately constant level despite the great variation in soil salinity”