Abstract
Based on the curvilinear relationship between carboxylation efficiency and leaf N in apple leaves, we hypothesized that deactivation of Rubisco accounts for the lack of response of photosynthesis to increasing leaf N under high N supply. A wide range of leaf N content (from 1.0 to 5.0 g·m –2 ) was achieved by fertigating bench-grafted Fuji/M26 apple trees for 6 weeks with different N concentrations using a modified Hoagland solution. Analysis of photosynthesis in response to intercellular CO 2 under both 21% and 2% O 2 indicated that photosynthesis at ambient CO 2 was mainly determined by the activity of Rubisco. Measurements of Rubisco activity revealed that initial Rubisco activity increased with leaf N up to 3.0 g·m –2 , then leveled off with further rise in leaf N, whereas 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. Photosynthesis at ambient CO 2 and carboxylation efficiency were both linearly correlated with initial Rubisco activity, but showed curvilinear relationships with total Rubisco activity and leaf N. As leaf N increased, photosynthetic nitrogen use efficiency declined with decreasing Rubisco activation state.
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Claims 9
Claim · model-written summary
Photosynthesis at ambient CO2 was mainly determined by Rubisco activity.
- Taxon
- Apple
Malus domesticat0 - Gene
- Rubiscoe0
- Outcome
- photosynthesis at ambient CO 2e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Apple”
e0“photosynthesis at ambient CO 2 was mainly determined by the activity of Rubisco”
Claim · model-written summary
Initial Rubisco activity rose with leaf N up to 3.0 g·m –2 and then leveled off.
- Taxon
- AppleMalus domesticat0
- Organ / stage
- leafe0
- Gene
- Rubiscoe0
- Outcome
- initial Rubisco activitye0
- Direction
- increasede0
- Value
- 3.0 g·m –2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Apple”
e0“initial Rubisco activity increased with leaf N up to 3.0 g·m –2 , then leveled off with further rise in leaf N”
Claim · model-written summary
Total Rubisco activity increased linearly throughout the leaf N range.
- Taxon
- AppleMalus domesticat0
- Organ / stage
- leafe0
- Gene
- Rubiscoe0
- Outcome
- total Rubisco activitye0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Apple”
e0“total Rubisco activity increased linearly with increasing leaf N throughout the leaf N range”
Claim · model-written summary
Rubisco activation state decreased with increasing leaf N.
- Taxon
- AppleMalus domesticat0
- Organ / stage
- leafe0
- Gene
- Rubiscoe0
- Outcome
- Rubisco activation statee0
- Direction
- decreasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Apple”
e0“Rubisco activation state decreased with increasing leaf N”
Claim · model-written summary
Photosynthesis at ambient CO2 correlated linearly with initial Rubisco activity.
- Taxon
- AppleMalus domesticat0
- Gene
- Rubiscoe0
- Outcome
- Photosynthesis at ambient CO 2e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Apple”
e0“Photosynthesis at ambient CO 2 and carboxylation efficiency were both linearly correlated with initial Rubisco activity”
Claim · model-written summary
Carboxylation efficiency correlated linearly with initial Rubisco activity.
- Taxon
- AppleMalus domesticat0
- Gene
- Rubiscoe0
- Outcome
- carboxylation efficiencye0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Apple”
e0“Photosynthesis at ambient CO 2 and carboxylation efficiency were both linearly correlated with initial Rubisco activity”
Claim · model-written summary
Photosynthesis at ambient CO2 had a curvilinear relationship with total Rubisco activity and leaf N.
- Taxon
- AppleMalus domesticat0
- Organ / stage
- leafe0
- Gene
- Rubiscoe0
- Outcome
- Photosynthesis at ambient CO 2e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Apple”
e0“Photosynthesis at ambient CO 2 and carboxylation efficiency were both linearly correlated with initial Rubisco activity, but showed curvilinear relationships with total Rubisco activity and leaf N.”
Claim · model-written summary
Carboxylation efficiency had a curvilinear relationship with total Rubisco activity and leaf N.
- Taxon
- AppleMalus domesticat0
- Organ / stage
- leafe0
- Gene
- Rubiscoe0
- Outcome
- carboxylation efficiencye0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Apple”
e0“carboxylation efficiency were both linearly correlated with initial Rubisco activity, but showed curvilinear relationships with total Rubisco activity and leaf N.”
Claim · model-written summary
Photosynthetic nitrogen use efficiency declined as leaf N rose and Rubisco activation state fell.
- Taxon
- AppleMalus domesticat0
- Organ / stage
- leafe0
- Gene
- Rubiscoe0
- Outcome
- photosynthetic nitrogen use efficiencye0
- Direction
- declinede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Apple”
e0“As leaf N increased, photosynthetic nitrogen use efficiency declined with decreasing Rubisco activation state.”