Abstract
Soil salinity and alkalinity are common constraints to crop productivity in low rainfall regions of the world. These two stresses have been extensively studied but not the combined stress of alkaline salinity. To examine the effects of mild salinity (50mM NaCl) combined with alkalinity (5mM NaHCO3) on growth of Brassica juncea (L.) Czern., 30 genotypes were grown in hydroponics. Growth of all genotypes was substantially reduced by alkaline salinity after 4 weeks of stress. Based on large genotypic differences, NDR 8501 and Vaibhav were selected as tolerant and Xinyou 5 as highly sensitive for further detailed physiological study. Shoot and root biomass and leaf area of the selected genotypes showed greater reduction under alkaline salinity than salinity or alkalinity alone. Alkalinity alone imposed larger negative effect on growth than salinity. K+ and P concentrations in both shoot and root were significantly reduced by alkaline salinity but small difference existed among the selected genotypes. Leaf Fe concentration in Xinyou 5 decreased under alkaline salinity below a critical level of 50mgkg-1, which explained why more chlorosis and a larger growth reduction occurred than in NDR 8501 and Vaibhav. Relatively large shoot and root Na+ concentration also had additional adverse effect on growth under alkaline salinity. Low tissue K+, P and Fe concentrations by alkalinity were the major factors that reduced growth in the selected genotypes. Growth reduction by salinity was mainly caused by Na+ toxicity. Shoot Na+ concentration of NDR 8501 and Vaibhav was almost half those in Xinyou 5, suggesting NDR 8501 and Vaibhav excluded more Na+. However, Na+ exclusion was reduced by more than 50% under alkaline salinity than salinity in the selected genotypes. In conclusion, our results demonstrated that alkaline salinity reduced uptake of essential nutrients and Na+ exclusion that resulted in more negative consequences on growth than salinity alone.
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Claims 17
Claim · model-written summary
Alkaline salinity substantially reduced growth of all genotypes after four weeks.
- Taxon
- genotypese0
- Treatment
- alkaline salinitye0
- Outcome
- Growthe0
- Direction
- reducede0
- Setting
- after 4 weeks of stresse0
Not reportedComparator
Verbatim
e0“Growth of all genotypes was substantially reduced by alkaline salinity after 4 weeks of stress.”
Claim · model-written summary
NDR 8501 and Vaibhav were tolerant, whereas Xinyou 5 was highly sensitive.
Verbatim
e0“NDR 8501 and Vaibhav were selected as tolerant and Xinyou 5 as highly sensitive”
Claim · model-written summary
Shoot biomass fell more under alkaline salinity than either stress alone.
Verbatim
e0“Shoot and root biomass and leaf area of the selected genotypes showed greater reduction under alkaline salinity than salinity or alkalinity alone.”
Claim · model-written summary
Root biomass fell more under alkaline salinity than either stress alone.
Verbatim
e0“Shoot and root biomass and leaf area of the selected genotypes showed greater reduction under alkaline salinity than salinity or alkalinity alone.”
Claim · model-written summary
Leaf area fell more under alkaline salinity than either stress alone.
Verbatim
e0“Shoot and root biomass and leaf area of the selected genotypes showed greater reduction under alkaline salinity than salinity or alkalinity alone.”
Claim · model-written summary
Alkalinity reduced growth more than salinity.
Not reportedTaxon
Verbatim
e0“Alkalinity alone imposed larger negative effect on growth than salinity.”
Claim · model-written summary
Alkaline salinity significantly reduced shoot and root K+ concentrations.
- Taxon
- selected genotypese0
- Organ / stage
- shoot and roote0
- Treatment
- alkaline salinitye0
- Outcome
- K+ and P concentrationse0
- Direction
- reducede0
Not reportedComparator
Verbatim
e0“K+ and P concentrations in both shoot and root were significantly reduced by alkaline salinity but small difference existed among the selected genotypes.”
Claim · model-written summary
Alkaline salinity significantly reduced shoot and root P concentrations.
- Taxon
- selected genotypese0
- Organ / stage
- shoot and roote0
- Treatment
- alkaline salinitye0
- Outcome
- P concentrationse0
- Direction
- reducede0
Not reportedComparator
Verbatim
e0“K+ and P concentrations in both shoot and root were significantly reduced by alkaline salinity but small difference existed among the selected genotypes.”
Claim · model-written summary
The selected genotypes differed little in shoot and root K+ and P concentrations.
Verbatim
e0“small difference existed among the selected genotypes.”
Claim · model-written summary
Xinyou 5 leaf Fe fell below 50mgkg-1 under alkaline salinity.
- Taxon
- Xinyou 5e0
- Treatment
- alkaline salinitye0
- Outcome
- Leaf Fe concentratione0
- Direction
- decreasede0
- Value
- 50mgkg-1e0
Not reportedComparator
Verbatim
e0“Leaf Fe concentration in Xinyou 5 decreased under alkaline salinity below a critical level of 50mgkg-1”
Claim · model-written summary
The low leaf Fe in Xinyou 5 explained greater chlorosis and growth reduction than in the tolerant genotypes.
Verbatim
e0“which explained why more chlorosis and a larger growth reduction occurred than in NDR 8501 and Vaibhav.”
Claim · model-written summary
High shoot and root Na+ concentrations further harmed growth under alkaline salinity.
Not reportedTaxon
Verbatim
e0“Relatively large shoot and root Na+ concentration also had additional adverse effect on growth under alkaline salinity.”
Claim · model-written summary
Low K+, P and Fe concentrations were major causes of reduced growth under alkalinity.
Verbatim
e0“Low tissue K+, P and Fe concentrations by alkalinity were the major factors that reduced growth in the selected genotypes.”
Claim · model-written summary
Na+ toxicity was identified as the main cause of salinity-related growth reduction.
Not reportedTaxon
Verbatim
e0“Growth reduction by salinity was mainly caused by Na+ toxicity.”
Claim · model-written summary
Shoot Na+ in NDR 8501 and Vaibhav was about half that in Xinyou 5.
Verbatim
e0“Shoot Na+ concentration of NDR 8501 and Vaibhav was almost half those in Xinyou 5”
Claim · model-written summary
NDR 8501 and Vaibhav were inferred to exclude more Na+.
Verbatim
e0“suggesting NDR 8501 and Vaibhav excluded more Na+.”
Claim · model-written summary
Na+ exclusion was over 50% lower under alkaline salinity than salinity in selected genotypes.
Verbatim
e0“Na+ exclusion was reduced by more than 50% under alkaline salinity than salinity in the selected genotypes.”