Abstract
To study the direct effects of photosynthesis on allocation of biomass by altering photosynthesis without altering leaf N or nitrate content, phosphoribulokinase (PRK) activity was decreased in transgenic tobacco (Nicotiana tabacum L.) with an inverted tobacco PRK cDNA and plants were grown at different N levels (0.4 and 5 mM NH4NO3). The activation state of PRK increased as the amount of enzyme was decreased genetically at both levels of N. At high N a 94% decrease in PRK activity had only a small effect (20%) on photosynthesis and growth. At low N a 94% decrease in PRK activity had a greater effect on leaf photosynthesis (decreased by up to 50%) and whole-plant photosynthesis (decreased by up to 35%) than at high N. These plants were up to 35% smaller than plants with higher PRK activities because they had less structural dry matter and less starch, which was decreased by 3- to 4-fold, but still accumulated to 24% to 31% of dry weight; young leaves contained more starch than older leaves in older plants. Leaves had a higher ion and water content, and specific leaf area was higher, but allocation between shoot and root was unaltered. In conclusion, low N in addition to a 94% decrease in PRK by antisense reduces the activity of PRK sufficient to diminish photosynthesis, which limits biomass production under conditions normally considered sink limited.
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Claims 11
Claim · model-written summary
PRK activation state rose as enzyme amount was genetically reduced at both nitrogen levels.
- Taxon
- tobacco (Nicotiana tabacum L.)
Nicotiana tabacume1 - Gene
- PRKe0
- Outcome
- activation state of PRKe0
- Direction
- increasede0
- Qualifier
- both levels of Ne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The activation state of PRK increased as the amount of enzyme was decreased genetically at both levels of N.”
e1“transgenic tobacco (Nicotiana tabacum L.)”
Claim · model-written summary
At high nitrogen, a 94% PRK activity decrease had only a 20% effect on photosynthesis and growth.
- Taxon
- tobacco (Nicotiana tabacum L.)Nicotiana tabacume1
- Treatment
- 94% decrease in PRK activitye0
- Outcome
- photosynthesis and growthe0
- Value
- 20%e0
- Qualifier
- high Ne0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At high N a 94% decrease in PRK activity had only a small effect (20%) on photosynthesis and growth.”
e1“transgenic tobacco (Nicotiana tabacum L.)”
Claim · model-written summary
At low nitrogen, 94% lower PRK activity decreased leaf photosynthesis by up to 50%.
- Taxon
- tobacco (Nicotiana tabacum L.)Nicotiana tabacume1
- Treatment
- 94% decrease in PRK activitye0
- Outcome
- leaf photosynthesise0
- Direction
- decreasede0
- Value
- 50%e0
- Qualifier
- low Ne0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At low N a 94% decrease in PRK activity had a greater effect on leaf photosynthesis (decreased by up to 50%)”
e1“transgenic tobacco (Nicotiana tabacum L.)”
Claim · model-written summary
At low nitrogen, 94% lower PRK activity decreased whole-plant photosynthesis by up to 35%.
- Taxon
- tobacco (Nicotiana tabacum L.)Nicotiana tabacume1
- Treatment
- 94% decrease in PRK activitye2
- Outcome
- whole-plant photosynthesise0
- Direction
- decreasede0
- Value
- 35%e0
- Qualifier
- low Ne2
- Comparator
- high Ne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“whole-plant photosynthesis (decreased by up to 35%) than at high N.”
e1“transgenic tobacco (Nicotiana tabacum L.)”
e2“At low N a 94% decrease in PRK activity”
Claim · model-written summary
Plants with lower PRK activity were up to 35% smaller than plants with higher PRK activity.
- Taxon
- tobacco (Nicotiana tabacum L.)Nicotiana tabacume1
- Gene
- PRKe0
- Outcome
- smallere0
- Direction
- smallere0
- Value
- 35%e0
- Comparator
- plants with higher PRK activitiese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“These plants were up to 35% smaller than plants with higher PRK activities”
e1“transgenic tobacco (Nicotiana tabacum L.)”
Claim · model-written summary
The smaller plants had less structural dry matter.
- Taxon
- tobacco (Nicotiana tabacum L.)Nicotiana tabacume1
- Outcome
- structural dry mattere0
- Direction
- lesse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“they had less structural dry matter”
e1“transgenic tobacco (Nicotiana tabacum L.)”
Claim · model-written summary
Starch decreased three- to fourfold but still reached 24% to 31% of dry weight.
- Taxon
- tobacco (Nicotiana tabacum L.)Nicotiana tabacume1
- Outcome
- starche0
- Direction
- decreasede0
- Value
- 3- to 4-folde0
- Qualifier
- 24% to 31% of dry weighte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“less starch, which was decreased by 3- to 4-fold, but still accumulated to 24% to 31% of dry weight”
e1“transgenic tobacco (Nicotiana tabacum L.)”
Claim · model-written summary
Young leaves contained more starch than older leaves in older plants.
- Taxon
- tobacco (Nicotiana tabacum L.)Nicotiana tabacume1
- Organ / stage
- young leavese0
- Outcome
- starche0
- Direction
- moree0
- Comparator
- older leavese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“young leaves contained more starch than older leaves in older plants.”
e1“transgenic tobacco (Nicotiana tabacum L.)”
Claim · model-written summary
Leaves had higher ion and water content.
- Taxon
- tobacco (Nicotiana tabacum L.)Nicotiana tabacume1
- Organ / stage
- Leavese0
- Outcome
- ion and water contente0
- Direction
- highere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaves had a higher ion and water content”
e1“transgenic tobacco (Nicotiana tabacum L.)”
Claim · model-written summary
Specific leaf area was higher.
- Taxon
- tobacco (Nicotiana tabacum L.)Nicotiana tabacume1
- Outcome
- specific leaf areae0
- Direction
- highere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“specific leaf area was higher”
e1“transgenic tobacco (Nicotiana tabacum L.)”
Claim · model-written summary
Shoot to root allocation was unaltered.
- Taxon
- tobacco (Nicotiana tabacum L.)Nicotiana tabacume1
- Outcome
- allocation between shoot and roote0
- Direction
- unalterede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“allocation between shoot and root was unaltered”
e1“transgenic tobacco (Nicotiana tabacum L.)”