Abstract
The present study was conducted to investigate in sunflower the processes of boron (B) uptake, intracellular compartmentation, and xylem translocation in response to B supply, ranging from deficiency to incipient toxicity, and to short-term changes in B supply. The experiments were conducted with two sunflower genotypes, selected on the basis of their susceptibility to knife-cut disease. It appears that the roots of the susceptible genotype of sunflower were more sensitive to low B contents in the solution media than the shoots. The decrease in root dry weight in high-B treatments could also indicate it was more sensitive to B toxicity. Though root dry weight decreased, the shoot/root dry-weight ratio was smaller in the resistant genotype, suggesting that this genotype would have a substantially larger root volume, capable of supporting the B demand of its shoots. The B contents in the water-insoluble residue (WIR) of roots were similar for all genotypes and treatments. In contrast, the B concentration in WIR of leaves reached values near saturation only when B started to accumulate in the cell sap (CS) of roots to the level as detected in CS of leaves. The critical values of B concentrations in shoot tissues would then be established after the B requirement for cell walls was satisfied and a proper metabolic B content in CS of roots was reached. Uptake efficiency (UE) values less than 1.00, detected as a result of treatments with high concentrations of B in the nutrient solution, suggested the presence of an exclusion mechanism that restricted B accumulation. The high UE value obtained with low-B treatments indicated that mechanisms other than mass flow had played a role in providing the acquired B.
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Claims 8
Claim · model-written summary
Roots of the susceptible sunflower genotype appear more sensitive to low B contents in the solution than shoots.
- Taxon
- sunflower
Helianthus annuuse1 - Material
- susceptible genotypee1
- Treatment
- low B contentse1
- Outcome
- rootse1
- Direction
- more sensitivee1
- Comparator
- shootse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Knife-Cut Disease in Sunflower”
e1“It appears that the roots of the susceptible genotype of sunflower were more sensitive to low B contents in the solution media than the shoots”
Claim · model-written summary
High-B treatments decreased root dry weight of sunflower.
- Taxon
- sunflowerHelianthus annuust0
- Treatment
- high-B treatmentse2
- Outcome
- root dry weighte2
- Direction
- decreasee2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Knife-Cut Disease in Sunflower”
e2“The decrease in root dry weight in high-B treatments”
Claim · model-written summary
The shoot/root dry-weight ratio of sunflower was smaller in the resistant genotype.
- Taxon
- sunflowerHelianthus annuust0
- Material
- resistant genotypee3
- Outcome
- shoot/root dry-weight ratioe3
- Direction
- smallere3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Knife-Cut Disease in Sunflower”
e3“the shoot/root dry-weight ratio was smaller in the resistant genotype”
Claim · model-written summary
B contents in the water-insoluble residue of sunflower roots were similar for all genotypes and treatments.
- Taxon
- sunflowerHelianthus annuust0
- Outcome
- B contents in the water-insoluble residue (WIR) of rootse4
- Qualifier
- similar for all genotypes and treatmentse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Knife-Cut Disease in Sunflower”
e4“The B contents in the water-insoluble residue (WIR) of roots were similar for all genotypes and treatments”
Claim · model-written summary
B concentration in leaf water-insoluble residue of sunflower reached near-saturation values only once B accumulated in root cell sap.
- Taxon
- sunflowerHelianthus annuust0
- Treatment
- B started to accumulate in the cell sap (CS) of rootse5
- Outcome
- B concentration in WIR of leavese5
- Direction
- reachede5
- Qualifier
- values near saturatione5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Knife-Cut Disease in Sunflower”
e5“the B concentration in WIR of leaves reached values near saturation only when B started to accumulate in the cell sap (CS) of roots”
Claim · model-written summary
Critical shoot B concentrations in sunflower are established after the cell-wall B requirement is satisfied and a proper metabolic B content in root cell sap is reached.
- Taxon
- sunflowerHelianthus annuust0
- Outcome
- critical values of B concentrations in shoot tissuese6
- Qualifier
- after the B requirement for cell walls was satisfiede6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Knife-Cut Disease in Sunflower”
e6“The critical values of B concentrations in shoot tissues would then be established after the B requirement for cell walls was satisfied and a proper metabolic B content in CS of roots was reached”
Claim · model-written summary
Low uptake efficiency at high B supply suggests an exclusion mechanism that restricts B accumulation in sunflower.
- Taxon
- sunflowerHelianthus annuust0
- Treatment
- high concentrations of B in the nutrient solutione7
- Outcome
- B accumulatione7
- Qualifier
- exclusion mechanisme7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Knife-Cut Disease in Sunflower”
e7“Uptake efficiency (UE) values less than 1.00, detected as a result of treatments with high concentrations of B in the nutrient solution, suggested the presence of an exclusion mechanism that restricted B accumulation”
Claim · model-written summary
High uptake efficiency with low-B treatments indicates mechanisms other than mass flow supply the acquired B in sunflower.
- Taxon
- sunflowerHelianthus annuust0
- Treatment
- low-B treatmentse1
- Outcome
- the acquired Be1
- Qualifier
- mechanisms other than mass flow had played a rolee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Knife-Cut Disease in Sunflower”
e1“The high UE value obtained with low-B treatments indicated that mechanisms other than mass flow had played a role in providing the acquired B”