Abstract
Based on the curvilinear relationship between leaf nitrogen content and the initial slope of the response of CO(2) assimilation (A:) to intercellular CO(2) concentrations (C:(i)) in apple, it is hypothesized that Rubisco activation state decreases with increasing leaf N content and this decreased activation state accounts for the curvilinear relationship between leaf N and CO(2) assimilation. A range of leaf N content (1.0-5.0 g m(-2)) was achieved by fertilizing bench-grafted Fuji/M.26 apple (Malus domestica Borkh.) trees for 45 d with different N concentrations, using a modified Hoagland's solution. Analysis of A:/C:(i) curves under saturating light indicated that CO(2) assimilation at ambient CO(2) fell within the Rubisco limitation region of the A:/C:(i) curves, regardless of leaf N status. Initial Rubisco activity showed a curvilinear response to leaf N. In contrast, total Rubisco activity increased linearly with increasing leaf N throughout the leaf N range. As a result, Rubisco activation state decreased with increasing leaf N. Both light-saturated CO(2) assimilation at ambient CO(2) and the initial slope of the A:/C:(i) curves were linearly related to initial Rubisco activity, but curvilinearly related to total Rubisco activity. The curvatures in the relationships of both light-saturated CO(2) assimilation at ambient CO(2) and the initial slope of the A:/C:(i) curves with total Rubisco activity were more pronounced than in their relationships with leaf N. This was because the ratio of total Rubisco activity to leaf N increased with increasing leaf N. As leaf N increased, photosynthetic N use efficiency declined with decreasing Rubisco activation state.
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Claims 9
Claim · model-written summary
Ambient-CO2 assimilation lay in the Rubisco limitation region regardless of leaf nitrogen.
- Taxon
- apple
Malus domesticat0 - Gene
- Rubiscoe0
- Outcome
- CO(2) assimilation at ambient CO(2) fell within the Rubisco limitation regione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CO(2) assimilation at ambient CO(2) fell within the Rubisco limitation region of the A:/C:(i) curves, regardless of leaf N status”
t0“apple leaves”
Claim · model-written summary
Initial Rubisco activity responded curvilinearly to leaf nitrogen.
- Taxon
- appleMalus domesticat0
- Gene
- Rubiscoe0
- Compound
- leaf Ne0
- Outcome
- Initial Rubisco activitye0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Initial Rubisco activity showed a curvilinear response to leaf N”
t0“apple leaves”
Claim · model-written summary
Total Rubisco activity rose linearly as leaf nitrogen increased.
- Taxon
- appleMalus domesticat0
- Gene
- Rubiscoe0
- Compound
- leaf Ne0
- Outcome
- total Rubisco activitye0
- Direction
- increased linearlye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“total Rubisco activity increased linearly with increasing leaf N throughout the leaf N range”
t0“apple leaves”
Claim · model-written summary
Rubisco activation state declined as leaf nitrogen increased.
- Taxon
- appleMalus domesticat0
- Gene
- Rubiscoe0
- Compound
- leaf Ne0
- Outcome
- Rubisco activation statee0
- Direction
- decreasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Rubisco activation state decreased with increasing leaf N”
t0“apple leaves”
Claim · model-written summary
Light-saturated CO2 assimilation related linearly to initial Rubisco activity and curvilinearly to total activity.
- Taxon
- appleMalus domesticat0
- Gene
- Rubiscoe0
- Outcome
- light-saturated CO(2) assimilation at ambient CO(2)e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“light-saturated CO(2) assimilation at ambient CO(2) and the initial slope of the A:/C:(i) curves were linearly related to initial Rubisco activity, but curvilinearly related to total Rubisco activity”
t0“apple leaves”
Claim · model-written summary
Initial A/Ci slope related linearly to initial Rubisco activity and curvilinearly to total activity.
- Taxon
- appleMalus domesticat0
- Gene
- Rubiscoe0
- Outcome
- initial slope of the A:/C:(i) curvese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“light-saturated CO(2) assimilation at ambient CO(2) and the initial slope of the A:/C:(i) curves were linearly related to initial Rubisco activity, but curvilinearly related to total Rubisco activity”
t0“apple leaves”
Claim · model-written summary
Those curvatures were stronger against total Rubisco activity than against leaf nitrogen.
- Taxon
- appleMalus domesticat0
- Gene
- Rubiscoe0
- Compound
- leaf Ne0
- Outcome
- curvatures in the relationships of both light-saturated CO(2) assimilation at ambient CO(2) and the initial slope of the A:/C:(i) curvese0
- Direction
- more pronouncede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The curvatures in the relationships of both light-saturated CO(2) assimilation at ambient CO(2) and the initial slope of the A:/C:(i) curves with total Rubisco activity were more pronounced than in their relationships with leaf N”
t0“apple leaves”
Claim · model-written summary
The ratio of total Rubisco activity to leaf nitrogen increased with leaf nitrogen.
- Taxon
- appleMalus domesticat0
- Gene
- Rubiscoe0
- Compound
- leaf Ne0
- Outcome
- ratio of total Rubisco activity to leaf Ne0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the ratio of total Rubisco activity to leaf N increased with increasing leaf N”
t0“apple leaves”
Claim · model-written summary
Photosynthetic nitrogen-use efficiency declined as leaf nitrogen rose and Rubisco activation fell.
- Taxon
- appleMalus domesticat0
- Gene
- Rubiscoe0
- Compound
- leaf Ne0
- Outcome
- photosynthetic N use efficiencye0
- Direction
- declinede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“As leaf N increased, photosynthetic N use efficiency declined with decreasing Rubisco activation state”
t0“apple leaves”