Abstract
Growth and photosynthetic response of lowland rice following complete submergence is related to the concentration of CO2 dissolved in floodwater. Submergence of plants in stagnant solution at low CO2 concentration or solution gassed with air at 0.03 kPa CO2 (equilibrium of 0.01 mol m-3 dissolved CO2) decreased carbohydrates, and little or no growth occurred. Plants submerged in solutions gassed with 3-20 kPa CO2 in air (equilibrium of 0.9-6 mol m-3 CO2) showed at most small decreases in carbohydrates, and growth was up to 100% of the non-submerged plants. At pH 7.5, there was little net photosynthetic O2 evolution by detached submerged leaves even at high HCO3- concentrations, which suggests that these rice leaves could utilise only CO2 and not HCO3-. At pH 6.5, O2 evolution in solutions in equilibrium with 7.4 kPa CO2 was 3-4 fold higher than in solutions in equilibrium with 0.6 kPa CO2. Photorespiration was indicated by a decrease in the rate of net O2 evolution with increasing external O2. In stagnant solutions this reduction of O2 evolution was pronounced; at a CO2 concentration of 0.25 mol m-3 net O2 evolution ceased when the O2 concentration in the water had reached only 0.125 mol m-3. The requirement of photosynthesis for a combination of high CO2 concentrations and low external O2 was presumably due to slow diffusion of these gases in the unstirred layer of solution around the leaves.
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Claims 10
Claim · model-written summary
Low CO2 submergence decreased rice carbohydrates.
- Taxon
- rice
Oryza sativat0 - Treatment
- Submergence of plants in stagnant solution at low CO2 concentratione0
- Outcome
- carbohydratese0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Submergence of plants in stagnant solution at low CO2 concentration or solution gassed with air at 0.03 kPa CO2 (equilibrium of 0.01 mol m-3 dissolved CO2) decreased carbohydrates”
t0“Rice”
Claim · model-written summary
Rice had little or no growth under low CO2 submergence.
- Taxon
- riceOryza sativat0
- Outcome
- growthe0
- Direction
- little or noe0
Not reportedTreatmentComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“little or no growth occurred”
t0“Rice”
Claim · model-written summary
Higher CO2 submergence caused at most small decreases in rice carbohydrates.
- Taxon
- riceOryza sativat0
- Treatment
- solutions gassed with 3-20 kPa CO2 in aire0
- Outcome
- carbohydratese0
- Direction
- small decreasese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Plants submerged in solutions gassed with 3-20 kPa CO2 in air (equilibrium of 0.9-6 mol m-3 CO2) showed at most small decreases in carbohydrates”
t0“Rice”
Claim · model-written summary
Growth under higher CO2 submergence reached up to 100% of non-submerged plants.
Not reportedTreatment
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“growth was up to 100% of the non-submerged plants”
t0“Rice”
Claim · model-written summary
At pH 7.5 detached submerged leaves had little net photosynthetic oxygen evolution even at high bicarbonate.
- Taxon
- riceOryza sativat0
- Organ / stage
- detached submerged leavese0
- Outcome
- net photosynthetic O2 evolutione0
- Qualifier
- even at high HCO3- concentrationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At pH 7.5, there was little net photosynthetic O2 evolution by detached submerged leaves even at high HCO3- concentrations”
t0“Rice”
Claim · model-written summary
Rice leaves apparently used CO2 rather than bicarbonate.
- Taxon
- riceOryza sativat0
- Organ / stage
- rice leavese0
- Outcome
- could utilise only CO2 and not HCO3-e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“these rice leaves could utilise only CO2 and not HCO3-”
t0“Rice”
Claim · model-written summary
At pH 6.5 oxygen evolution at 7.4 kPa CO2 was 3-4 fold higher than at 0.6 kPa.
- Taxon
- riceOryza sativat0
- Treatment
- 7.4 kPa CO2e0
- Outcome
- O2 evolutione0
- Direction
- highere0
- Value
- 3-4 folde0
- Comparator
- 0.6 kPa CO2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At pH 6.5, O2 evolution in solutions in equilibrium with 7.4 kPa CO2 was 3-4 fold higher than in solutions in equilibrium with 0.6 kPa CO2”
t0“Rice”
Claim · model-written summary
Increasing external oxygen decreased net oxygen evolution, indicating photorespiration.
- Taxon
- riceOryza sativat0
- Treatment
- increasing external O2e0
- Outcome
- rate of net O2 evolutione0
- Direction
- decreasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Photorespiration was indicated by a decrease in the rate of net O2 evolution with increasing external O2”
t0“Rice”
Claim · model-written summary
In stagnant solution at 0.25 mol m-3 CO2, net oxygen evolution ceased at 0.125 mol m-3 oxygen.
- Taxon
- riceOryza sativat0
- Outcome
- net O2 evolution ceasede0
- Value
- 0.125 mol m-3e0
- Qualifier
- at a CO2 concentration of 0.25 mol m-3e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“at a CO2 concentration of 0.25 mol m-3 net O2 evolution ceased when the O2 concentration in the water had reached only 0.125 mol m-3”
t0“Rice”
Claim · model-written summary
Slow gas diffusion around leaves was proposed to explain the need for high CO2 and low external oxygen.
- Taxon
- riceOryza sativat0
- Outcome
- requirement of photosynthesis for a combination of high CO2 concentrations and low external O2e0
- Qualifier
- slow diffusion of these gases in the unstirred layer of solution around the leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The requirement of photosynthesis for a combination of high CO2 concentrations and low external O2 was presumably due to slow diffusion of these gases in the unstirred layer of solution around the leaves”
t0“Rice”
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