Abstract
Removal of the shoot above the primary node (detopping) of 3‐week‐old bean plants ( Phaseolus vulgaris L. cv. Contender) altered the metabolism and development of the remaining leaves. An increase in levels of chlorophyll, protein, stomatal opening, photosynthesis and growth, i.e. rejuvenation of primary leaves, was established within 7 days of detopping. These levels were maintained while the primary leaves of equivalent intact plants senesced. The flux of xylem solution (mineral ions, cytokinins and water) into leaves is related to the leaf area to be supplied and root supply capacity; it has been suggested that detopping leads to an increased availability of root‐supplied solutes and hence rejuvenation of the remaining leaves. This assumes however that root output of solutes is not decreased by the defoliation treatment. We found that root output of ions (electrical conductivity of passive xylem exudate) in detopped plants was 30% lower than in intact plants after 24 h and 60% lower after 7 days. The output of Ca 2+ , Mg 2+ and K + were similarly reduced 7 and 14 days after detopping as were fresh and dry weights of roots. Furthermore, neither the calculated xylem flux of ions nor directly measured levels of Ca 2+ , Mg 2+ and K + were significantly increased in leaves of detopped plants during their rejuvenation. We therefore conclude that root output is tightly coupled to shoot demand and that the apparent rejuvenation of primary leaves caused by detopping bean plants is not a consequence of increased xylem flux of mineral ions into the leaves.
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Claims 9
Claim · model-written summary
Detopping increased chlorophyll, protein, stomatal opening, photosynthesis and growth within seven days.
- Taxon
- bean plantse1
- Organ / stage
- primary leavese0
- Treatment
- detoppinge0
- Outcome
- levels of chlorophyll, protein, stomatal opening, photosynthesis and growthe0
- Direction
- increasee0
- Qualifier
- within 7 dayse0
Not reportedComparator
Verbatim
e0“An increase in levels of chlorophyll, protein, stomatal opening, photosynthesis and growth, i.e. rejuvenation of primary leaves, was established within 7 days of detopping.”
e1“3‐week‐old bean plants ( Phaseolus vulgaris L. cv. Contender)”
Claim · model-written summary
Detopped primary leaves maintained these levels while equivalent intact leaves senesced.
Verbatim
e0“These levels were maintained while the primary leaves of equivalent intact plants senesced.”
e1“3‐week‐old bean plants ( Phaseolus vulgaris L. cv. Contender)”
Claim · model-written summary
Root ion output in detopped plants was 30% lower after 24 hours than intact plants.
Verbatim
e0“We found that root output of ions (electrical conductivity of passive xylem exudate) in detopped plants was 30% lower than in intact plants after 24 h and 60% lower after 7 days.”
e1“3‐week‐old bean plants ( Phaseolus vulgaris L. cv. Contender)”
Claim · model-written summary
Root ion output in detopped plants was 60% lower after seven days than intact plants.
Verbatim
e0“We found that root output of ions (electrical conductivity of passive xylem exudate) in detopped plants was 30% lower than in intact plants after 24 h and 60% lower after 7 days.”
e1“3‐week‐old bean plants ( Phaseolus vulgaris L. cv. Contender)”
Claim · model-written summary
Root outputs of calcium, magnesium and potassium and root weights were similarly reduced after detopping.
- Taxon
- bean plantse1
- Treatment
- detoppinge0
- Outcome
- output of Ca 2+ , Mg 2+ and K +e0
- Direction
- reducede0
- Qualifier
- 7 and 14 dayse0
Not reportedComparator
Verbatim
e0“The output of Ca 2+ , Mg 2+ and K + were similarly reduced 7 and 14 days after detopping as were fresh and dry weights of roots.”
e1“3‐week‐old bean plants ( Phaseolus vulgaris L. cv. Contender)”
Claim · model-written summary
Root fresh and dry weights were reduced after detopping.
Not reportedComparator
Verbatim
e0“The output of Ca 2+ , Mg 2+ and K + were similarly reduced 7 and 14 days after detopping as were fresh and dry weights of roots.”
e1“3‐week‐old bean plants ( Phaseolus vulgaris L. cv. Contender)”
Claim · model-written summary
Calculated xylem ion flux and measured leaf calcium, magnesium and potassium were not significantly increased during rejuvenation.
Verbatim
e0“Furthermore, neither the calculated xylem flux of ions nor directly measured levels of Ca 2+ , Mg 2+ and K + were significantly increased in leaves of detopped plants during their rejuvenation.”
e1“3‐week‐old bean plants ( Phaseolus vulgaris L. cv. Contender)”
Claim · model-written summary
Leaf calcium, magnesium and potassium levels were not significantly increased in detopped plants during rejuvenation.
Verbatim
e0“Furthermore, neither the calculated xylem flux of ions nor directly measured levels of Ca 2+ , Mg 2+ and K + were significantly increased in leaves of detopped plants during their rejuvenation.”
e1“3‐week‐old bean plants ( Phaseolus vulgaris L. cv. Contender)”
Claim · model-written summary
The authors conclude root ion output is coupled to shoot demand and rejuvenation is not caused by increased ion flux.
- Taxon
- bean plantse0
- Outcome
- root output is tightly coupled to shoot demande0
- Qualifier
- not a consequence of increased xylem flux of mineral ions into the leavese0
Not reportedDirection
Verbatim
e0“We therefore conclude that root output is tightly coupled to shoot demand and that the apparent rejuvenation of primary leaves caused by detopping bean plants is not a consequence of increased xylem flux of mineral ions into the leaves.”
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