Abstract
Root elongation by wheat seedlings (Triticum aestivum L. cv. Scout 66) was not inhibited by NaCl or KCl up to 130 mM in culture solutions or by high Na+ (2 mg g−1 FW) or K+ (4 mg g−1 FW) in the root tissue, provided that [Ca2+]>2 mM in the rooting medium. At [NaCl], [KCl], or [mannitol] >250 mOs, root elongation was progressively inhibited, irrespective of high [Ca2+]. In contrast, shoot elongation was sensitive to any diminution of water potential, and Ca2+ alleviated the toxicity only weakly. At solute concentrations <250 mOs, the following interactions were observed. Ca2+ alleviated Na+ and K+ toxicity to roots by at least three separate mechanisms. K+ was more toxic to roots than Na+, but Na+ was more toxic to shoots. Low levels of K+ relieved Na+ toxicity, but low levels of Na+ enhanced K+ toxicity. Tissue concentrations of Na+ were reduced by Ca2+ and K+ in the rooting medium, and tissue concentrations of K+ were enhanced by Ca2+ and Na+. Several hypotheses relating to salinity toxicity can be evaluated, at least for wheat seedlings. The osmoticant hypothesis (salinity intoxication occurs because of diminished water potential) is true for shoots at all salinity levels, but is true for roots only at high salinity. The Ca2+-displacement hypothesis (Na+ is toxic because it displaces Ca2+ from the cell surface) is correct, but often of minor importance. The K+-depletion hypothesis (Na+ is toxic because it causes a loss of K+ from plant tissues) is false. The Cl−-toxicity hypothesis (the apparent toxicity of Na+ is induced by associated Cl−) is false. The results indicate that, apart from osmotic effects, high levels of Na+ in the rooting medium and in the tissues are not toxic unless Ca2+ is also deficient, a condition probably leading to inadequate compartmentation and excessive cytoplasmic accumulation. This study related growth to ion activities at plasma-membrane surfaces. These activities were computed by a Gouy-Chapman-Stern model then incorporated into non-linear growth models for growth versus toxicants and ameliorants.
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Claims 10
Claim · model-written summary
Root elongation was not inhibited by NaCl or KCl up to 130 mM when calcium exceeded 2 mM.
- Taxon
- wheat seedlings
Triticum aestivume0 - Treatment
- NaCl or KCl up to 130 mMe0
- Outcome
- Root elongatione0
- Direction
- not inhibitede0
- Qualifier
- [Ca2+]>2 mMe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Root elongation by wheat seedlings (Triticum aestivum L. cv. Scout 66) was not inhibited by NaCl or KCl up to 130 mM in culture solutions or by high Na+ (2 mg g−1 FW) or K+ (4 mg g−1 FW) in the root tissue, provided that [Ca2+]>2 mM in the rooting medium”
Claim · model-written summary
Root elongation was inhibited progressively above 250 mOs regardless of calcium.
- Taxon
- wheat seedlingsTriticum aestivume0
- Treatment
- [NaCl], [KCl], or [mannitol] >250 mOse1
- Outcome
- root elongatione1
- Direction
- progressively inhibitede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“wheat seedlings (Triticum aestivum L. cv. Scout 66)”
e1“At [NaCl], [KCl], or [mannitol] >250 mOs, root elongation was progressively inhibited, irrespective of high [Ca2+]”
Claim · model-written summary
Shoot elongation was sensitive to decreased water potential and calcium alleviated toxicity weakly.
- Taxon
- wheat seedlingsTriticum aestivume0
- Outcome
- shoot elongatione1
- Direction
- sensitivee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“wheat seedlings (Triticum aestivum L. cv. Scout 66)”
e1“shoot elongation was sensitive to any diminution of water potential, and Ca2+ alleviated the toxicity only weakly”
Claim · model-written summary
Calcium alleviated sodium and potassium root toxicity by at least three mechanisms.
- Taxon
- wheat seedlingsTriticum aestivume0
- Compound
- Ca2+e1
- Outcome
- Na+ and K+ toxicity to rootse1
- Qualifier
- at least three separate mechanismse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“wheat seedlings (Triticum aestivum L. cv. Scout 66)”
e1“Ca2+ alleviated Na+ and K+ toxicity to roots by at least three separate mechanisms”
Claim · model-written summary
Potassium was more toxic to roots than sodium.
- Taxon
- wheat seedlingsTriticum aestivume0
- Compound
- K+e1
- Outcome
- toxic to rootse1
- Direction
- moree1
- Comparator
- Na+e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“wheat seedlings (Triticum aestivum L. cv. Scout 66)”
e1“K+ was more toxic to roots than Na+”
Claim · model-written summary
Sodium was more toxic to shoots than potassium.
- Taxon
- wheat seedlingsTriticum aestivume0
- Compound
- Na+e1
- Outcome
- toxic to shootse1
- Direction
- moree1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“wheat seedlings (Triticum aestivum L. cv. Scout 66)”
e1“Na+ was more toxic to shoots”
Claim · model-written summary
Low potassium relieved sodium toxicity.
- Taxon
- wheat seedlingsTriticum aestivume0
- Treatment
- Low levels of K+e1
- Outcome
- Na+ toxicitye1
- Direction
- relievede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“wheat seedlings (Triticum aestivum L. cv. Scout 66)”
e1“Low levels of K+ relieved Na+ toxicity”
Claim · model-written summary
Low sodium enhanced potassium toxicity.
- Taxon
- wheat seedlingsTriticum aestivume0
- Treatment
- low levels of Na+e1
- Outcome
- K+ toxicitye1
- Direction
- enhancede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“wheat seedlings (Triticum aestivum L. cv. Scout 66)”
e1“low levels of Na+ enhanced K+ toxicity”
Claim · model-written summary
Calcium and potassium in rooting medium reduced tissue sodium concentrations.
- Taxon
- wheat seedlingsTriticum aestivume0
- Treatment
- Ca2+ and K+ in the rooting mediume1
- Outcome
- Tissue concentrations of Na+e1
- Direction
- reducede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“wheat seedlings (Triticum aestivum L. cv. Scout 66)”
e1“Tissue concentrations of Na+ were reduced by Ca2+ and K+ in the rooting medium”
Claim · model-written summary
Calcium and sodium enhanced tissue potassium concentrations.
- Taxon
- wheat seedlingsTriticum aestivume0
- Treatment
- Ca2+ and Na+e1
- Outcome
- tissue concentrations of K+e1
- Direction
- enhancede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“wheat seedlings (Triticum aestivum L. cv. Scout 66)”
e1“tissue concentrations of K+ were enhanced by Ca2+ and Na+”
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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.