Abstract
When spinach plants were transferred to nutrient solutions without phosphorus, the photosynthetic rate per unit leaf area gradually declined. Stomatal conductance also decreased but was not the sole cause of the decreased photosynthetic rate because the partial pressure of CO2 in the intercellular spaces (CI) was unaltered. Measurements of the photosynthetic rate as a function of CI indicated reductions in both ribulosebisphosphate (RuP2) carboxylase activity and RuP2 regeneration capacity. From assays of RuP2 carboxylase activity in vitro and 'percentage activation', it was concluded that low-P leaves had less enzyme per unit area than controls and that the enzyme was also less activated. The photosynthetic quantum yield was reduced by phosphorus deficiency with no effect on leaf absorptance or chlorophyll content. The reduced quantum yield was accompanied by changes in chlorophyll fluorescence of photosystems I and II measured at 77K. However, since phosphorus deficiency did not affect the uncoupled rate of whole-chain electron transport in vitro, some factor(s) other than photoinhibition probably contributed to the reduced quantum yield. The lack of effect on this electron-transport rate also indicates that the maximal RuP2 regeneration rate in low-P leaves was not limited by the amount of electon-transport components. At ambient [CO2], low-P leaves had significantly less RuP2 and 3-phosphoglycerate (PGA) than controls and the response of photosynthesis to low [O2] was similar to control leaves. Therefore photosynthesis did not appear to be limited by triose-phosphate utilization. The low concentrations of RuP2 and PGA (and presumably other Calvin-cycle intermediates) might have reduced the rate of the Calvin cycle. After returning low-P plants to nutrient solutions with PO4, the percentage activation of RuP2 carboxylase, amounts of RuP2 and PGA, quantum yield and maximal RuP2 regeneration rate increased within 24 h. The quantum yield and photosynthetic rate at higher irradiance also increased when leaf discs from low-P plants were floated on 10 mM PO4 solutions for 2 h.
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Claims 16
Claim · model-written summary
Photosynthetic rate per unit leaf area of spinach declined gradually when plants were moved to solution without phosphorus.
- Taxon
- spinach
Spinacia oleraceae0 - Treatment
- without phosphoruse0
- Outcome
- photosynthetic rate per unit leaf areae0
- Direction
- declinede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When spinach plants were transferred to nutrient solutions without phosphorus, the photosynthetic rate per unit leaf area gradually declined”
Claim · model-written summary
Stomatal conductance decreased in phosphorus-deprived spinach.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- without phosphoruse0
- Outcome
- Stomatal conductancee1
- Direction
- decreasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When spinach plants were transferred to nutrient solutions without phosphorus, the photosynthetic rate per unit leaf area gradually declined”
e1“Stomatal conductance also decreased but was not the sole cause of the decreased photosynthetic rate because the partial pressure of CO2 in the intercellular spaces (CI) was unaltered”
Claim · model-written summary
Phosphorus-deprived spinach showed reduced ribulosebisphosphate (RuP2) carboxylase activity and RuP2 regeneration capacity.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- without phosphoruse0
- Outcome
- ribulosebisphosphate (RuP2) carboxylase activity and RuP2 regeneration capacitye2
- Direction
- reductionse2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When spinach plants were transferred to nutrient solutions without phosphorus, the photosynthetic rate per unit leaf area gradually declined”
e2“Measurements of the photosynthetic rate as a function of CI indicated reductions in both ribulosebisphosphate (RuP2) carboxylase activity and RuP2 regeneration capacity”
Claim · model-written summary
Low-P spinach leaves had less Rubisco enzyme per unit area than control leaves.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- low-Pe3
- Outcome
- enzyme per unit areae3
- Direction
- lesse3
- Comparator
- controlse3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When spinach plants were transferred to nutrient solutions without phosphorus, the photosynthetic rate per unit leaf area gradually declined”
e3“low-P leaves had less enzyme per unit area than controls and that the enzyme was also less activated”
Claim · model-written summary
Rubisco in low-P spinach leaves was less activated than in controls.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- low-Pe3
- Outcome
- activatede3
- Direction
- lesse3
- Comparator
- controlse3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When spinach plants were transferred to nutrient solutions without phosphorus, the photosynthetic rate per unit leaf area gradually declined”
e3“low-P leaves had less enzyme per unit area than controls and that the enzyme was also less activated”
Claim · model-written summary
Phosphorus deficiency reduced the photosynthetic quantum yield of spinach.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- phosphorus deficiencye4
- Outcome
- photosynthetic quantum yielde4
- Direction
- reducede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When spinach plants were transferred to nutrient solutions without phosphorus”
e4“The photosynthetic quantum yield was reduced by phosphorus deficiency with no effect on leaf absorptance or chlorophyll content”
Claim · model-written summary
Phosphorus deficiency had no effect on leaf absorptance or chlorophyll content of spinach.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- phosphorus deficiencye4
- Outcome
- leaf absorptance or chlorophyll contente4
- Direction
- no_changeinferrede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When spinach plants were transferred to nutrient solutions without phosphorus”
e4“The photosynthetic quantum yield was reduced by phosphorus deficiency with no effect on leaf absorptance or chlorophyll content”
Claim · model-written summary
The reduced quantum yield of spinach was accompanied by changes in chlorophyll fluorescence of photosystems I and II.
- Taxon
- spinachSpinacia oleraceae0
- Outcome
- chlorophyll fluorescence of photosystems I and IIe5
- Direction
- changese5
- Qualifier
- measured at 77Ke5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When spinach plants were transferred to nutrient solutions without phosphorus”
e5“The reduced quantum yield was accompanied by changes in chlorophyll fluorescence of photosystems I and II measured at 77K”
Claim · model-written summary
Phosphorus deficiency did not affect the uncoupled rate of whole-chain electron transport of spinach in vitro.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- phosphorus deficiencye6
- Outcome
- uncoupled rate of whole-chain electron transport in vitroe6
- Direction
- no_changeinferrede6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When spinach plants were transferred to nutrient solutions without phosphorus”
e6“since phosphorus deficiency did not affect the uncoupled rate of whole-chain electron transport in vitro”
Claim · model-written summary
Low-P spinach leaves had significantly less RuP2 and 3-phosphoglycerate (PGA) than controls at ambient CO2.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- low-Pe7
- Outcome
- RuP2 and 3-phosphoglycerate (PGA)e7
- Direction
- significantly lesse7
- Qualifier
- At ambient [CO2]e7
- Comparator
- controlse7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When spinach plants were transferred to nutrient solutions without phosphorus, the photosynthetic rate per unit leaf area gradually declined”
e7“At ambient [CO2], low-P leaves had significantly less RuP2 and 3-phosphoglycerate (PGA) than controls”
Claim · model-written summary
The response of spinach photosynthesis to low O2 was similar in low-P leaves and control leaves.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- low-Pe7
- Outcome
- response of photosynthesis to low [O2]e1
- Direction
- no_changeinferrede1
- Comparator
- control leavese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When spinach plants were transferred to nutrient solutions without phosphorus, the photosynthetic rate per unit leaf area gradually declined”
e7“At ambient [CO2], low-P leaves had significantly less RuP2 and 3-phosphoglycerate (PGA) than controls”
e1“the response of photosynthesis to low [O2] was similar to control leaves”
Claim · model-written summary
Photosynthesis of spinach did not appear to be limited by triose-phosphate utilization.
- Taxon
- spinachSpinacia oleraceae0
- Outcome
- photosynthesise1
- Qualifier
- did not appear to be limited by triose-phosphate utilizatione1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When spinach plants were transferred to nutrient solutions without phosphorus”
e1“Therefore photosynthesis did not appear to be limited by triose-phosphate utilization”
Claim · model-written summary
Low concentrations of RuP2 and PGA might have reduced the rate of the Calvin cycle in low-P spinach.
- Taxon
- spinachSpinacia oleraceae0
- Compound
- RuP2 and PGAe1
- Outcome
- rate of the Calvin cyclee1
- Qualifier
- might have reducede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When spinach plants were transferred to nutrient solutions without phosphorus”
e1“The low concentrations of RuP2 and PGA (and presumably other Calvin-cycle intermediates) might have reduced the rate of the Calvin cycle”
Claim · model-written summary
After low-P plants were returned to PO4 solution, Rubisco activation and amounts of RuP2 and PGA increased within 24 h.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- returning low-P plants to nutrient solutions with PO4e1
- Outcome
- percentage activation of RuP2 carboxylase, amounts of RuP2 and PGAe1
- Direction
- increasede1
- Qualifier
- within 24 he1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When spinach plants were transferred to nutrient solutions without phosphorus”
e1“After returning low-P plants to nutrient solutions with PO4, the percentage activation of RuP2 carboxylase, amounts of RuP2 and PGA, quantum yield and maximal RuP2 regeneration rate increased within 24 h”
Claim · model-written summary
After low-P plants were returned to PO4 solution, quantum yield and maximal RuP2 regeneration rate increased within 24 h.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- returning low-P plants to nutrient solutions with PO4e1
- Outcome
- quantum yield and maximal RuP2 regeneration ratee1
- Direction
- increasede1
- Qualifier
- within 24 he1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When spinach plants were transferred to nutrient solutions without phosphorus”
e1“After returning low-P plants to nutrient solutions with PO4, the percentage activation of RuP2 carboxylase, amounts of RuP2 and PGA, quantum yield and maximal RuP2 regeneration rate increased within 24 h”
Claim · model-written summary
Quantum yield and photosynthetic rate at higher irradiance of low-P spinach leaves increased when floated on 10 mM PO4 for 2 h.
- Taxon
- spinachSpinacia oleraceae0
- Treatment
- leaf discs from low-P plants were floated on 10 mM PO4 solutions for 2 he1
- Outcome
- quantum yield and photosynthetic rate at higher irradiancee1
- Direction
- increasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When spinach plants were transferred to nutrient solutions without phosphorus”
e1“The quantum yield and photosynthetic rate at higher irradiance also increased when leaf discs from low-P plants were floated on 10 mM PO4 solutions for 2 h”
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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.