Abstract
The effects of CO(2)-limited photosynthesis on (15)NO(3) (-) uptake and reduction by maize (Zea mays, DeKalb XL-45) seedlings were examined in relation to concurrent effects of CO(2) stress on carbohydrate levels and in vitro nitrate reductase activities. During a 10-hour period in CO(2)-depleted air (30 microliters of CO(2)/ per liter), cumulative (15)NO(3) (-) uptake and reduction were restricted 22 and 82%, respectively, relative to control seedlings exposed to ambient air containing 450 microliters of CO(2) per liter. The comparable values for roots of decapitated maize seedlings, the shoots of which had previously been subjected to CO(2) stress, were 30 and 42%. The results demonstrate that reduction of entering nitrate by roots as well as shoots was regulated by concurrent photosynthesis. Although in vitro nitrate reductase activity of both tissues declined by 60% during a 10-hour period of CO(2) stress, the remaining activity was greatly in excess of that required to catalyze the measured rate of (15)NO(3) (-) reduction. Root respiration and soluble carbohydrate levels in root tissue were also decreased by CO(2) stress. Collectively, the results indicate that nitrate uptake and reduction were regulated by the supply of energy and carbon skeletons required to support these processes, rather than by the potential enzymatic capacity to catalyze nitrate reduction, as measured by in vitro nitrate reductase activity.
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Claims 8
Claim · model-written summary
CO2-depleted air restricted cumulative nitrate uptake by 22% relative to ambient air.
- Material
- DeKalb XL-45e1
- Treatment
- CO(2)-depleted air (30 microliters of CO(2)/ per liter)e0
- Outcome
- (15)NO(3) (-) uptakee0
- Direction
- restrictede0
- Value
- 22e0
- Comparator
- control seedlings exposed to ambient air containing 450 microliters of CO(2) per litere0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“During a 10-hour period in CO(2)-depleted air (30 microliters of CO(2)/ per liter), cumulative (15)NO(3) (-) uptake and reduction were restricted 22 and 82%, respectively, relative to control seedlings exposed to ambient air containing 450 microliters of CO(2) per liter”
t0“Nitrate Reduction in Response to CO2-Limited Photosynthesis”
e1“maize (Zea mays, DeKalb XL-45) seedlings”
Claim · model-written summary
CO2-depleted air restricted cumulative nitrate reduction by 82% relative to ambient air.
- Material
- DeKalb XL-45e1
- Treatment
- CO(2)-depleted air (30 microliters of CO(2)/ per liter)e0
- Outcome
- (15)NO(3) (-) uptake and reductione0
- Direction
- restrictede0
- Value
- 82%e0
- Comparator
- control seedlings exposed to ambient air containing 450 microliters of CO(2) per litere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“During a 10-hour period in CO(2)-depleted air (30 microliters of CO(2)/ per liter), cumulative (15)NO(3) (-) uptake and reduction were restricted 22 and 82%, respectively, relative to control seedlings exposed to ambient air containing 450 microliters of CO(2) per liter”
e1“maize (Zea mays, DeKalb XL-45) seedlings”
Claim · model-written summary
Roots of decapitated maize seedlings showed a 30% comparable restriction in nitrate uptake.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The comparable values for roots of decapitated maize seedlings, the shoots of which had previously been subjected to CO(2) stress, were 30 and 42%”
Claim · model-written summary
Roots of decapitated maize seedlings showed a 42% comparable restriction in nitrate reduction.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The comparable values for roots of decapitated maize seedlings, the shoots of which had previously been subjected to CO(2) stress, were 30 and 42%”
Claim · model-written summary
In vitro nitrate reductase activity in roots and shoots declined by 60% during CO2 stress.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in vitro nitrate reductase activity of both tissues declined by 60% during a 10-hour period of CO(2) stress”
e1“maize seedlings”
Claim · model-written summary
Remaining nitrate reductase activity exceeded that needed for measured nitrate reduction.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the remaining activity was greatly in excess of that required to catalyze the measured rate of (15)NO(3) (-) reduction”
e1“maize seedlings”
Claim · model-written summary
CO2 stress decreased root respiration and soluble carbohydrate levels.
- Organ / stage
- root tissuee0
- Treatment
- CO(2) stresse0
- Outcome
- Root respiration and soluble carbohydrate levelse0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Root respiration and soluble carbohydrate levels in root tissue were also decreased by CO(2) stress”
e1“maize seedlings”
Claim · model-written summary
The authors interpret nitrate uptake and reduction as regulated by energy and carbon skeleton supply.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“nitrate uptake and reduction were regulated by the supply of energy and carbon skeletons required to support these processes”
e1“maize seedlings”
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9 papers more in this group
See all 13 papers →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.