Abstract
Tobacco plants were grown in sunlit, controlled-environment cabinets, and their growth and gas exchange were followed from shortly after emergence to 90 days from sowing. There were three major findings: 1. Summed over all leaves, dark respiration remained at 6-7% of net photosynthesis for a lengthy period (50-90 days from sowing), but in younger plants the fraction reached as high as 18%. 2. In the 12 leaves monitored from their emergence to full expansion, net photosynthesis (Pn) followed a similar time course, even though the first and last leaves in this group emerged nearly 40 days apart and there was a 100-fold difference in final area (Amax). For a sequence of nine of these leaves, the agreement was so close that their photosynthetic histories could be represented by a single relationship with developmental time. Peak Pn was consistently attained at about 37% Amax, when peak dA/dt occurred, and it was held for only 3-5 days. The subsequent decline reduced Pn to less than one-third of peak Pn at Amax. 3. Data for the nitrogen content (w/w) of the leaves after 37% Amax could be combined in a manner similar to that described for Pn. Pn, nitrogen content and leaf ontogeny were therefore directly related after peak Pn had been attained. The bearing of these findings on the study of photosynthesis in dicotyledonous species is discussed.
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Claims 9
Claim · model-written summary
Across tobacco leaves, dark respiration stayed at 6-7% of net photosynthesis from 50 to 90 days.
- Taxon
- Tobacco Plant
Nicotiana tabacumt0 - Outcome
- dark respiratione0
- Direction
- remainede0
- Value
- 6-7%e0
- Qualifier
- 50-90 days from sowinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“dark respiration remained at 6-7% of net photosynthesis for a lengthy period (50-90 days from sowing)”
t0“Tobacco Plant”
Claim · model-written summary
In younger tobacco plants, dark respiration reached 18% of net photosynthesis.
- Taxon
- Tobacco PlantNicotiana tabacumt0
- Outcome
- fractione0
- Direction
- reached as high ase0
- Value
- 18%e0
- Qualifier
- younger plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in younger plants the fraction reached as high as 18%”
t0“Tobacco Plant”
Claim · model-written summary
Twelve tobacco leaves followed a similar net photosynthesis time course despite a 40-day emergence span and 100-fold final-area difference.
- Taxon
- Tobacco PlantNicotiana tabacumt0
- Outcome
- net photosynthesis (Pn)e0
- Direction
- similare0
- Qualifier
- 100-fold difference in final areae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“net photosynthesis (Pn) followed a similar time course, even though the first and last leaves in this group emerged nearly 40 days apart and there was a 100-fold difference in final area (Amax)”
t0“Tobacco Plant”
Claim · model-written summary
Nine tobacco leaves had photosynthetic histories represented by one relation with developmental time.
- Taxon
- Tobacco PlantNicotiana tabacumt0
- Outcome
- photosynthetic historiese0
- Qualifier
- single relationship with developmental timee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“their photosynthetic histories could be represented by a single relationship with developmental time”
t0“Tobacco Plant”
Claim · model-written summary
Peak tobacco leaf net photosynthesis occurred near 37% final area, alongside peak leaf expansion rate.
- Taxon
- Tobacco PlantNicotiana tabacumt0
- Outcome
- Peak Pne0
- Direction
- Peake0
- Value
- 37% Amaxe0
- Qualifier
- peak dA/dte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Peak Pn was consistently attained at about 37% Amax, when peak dA/dt occurred”
t0“Tobacco Plant”
Claim · model-written summary
Peak tobacco leaf photosynthesis lasted only 3-5 days.
- Taxon
- Tobacco PlantNicotiana tabacumt0
- Outcome
- helde0
- Value
- 3-5 dayse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“it was held for only 3-5 days”
t0“Tobacco Plant”
Claim · model-written summary
Tobacco leaf photosynthesis fell below one-third of its peak by full expansion.
- Taxon
- Tobacco PlantNicotiana tabacumt0
- Outcome
- Pne0
- Direction
- declinee0
- Value
- less than one-third of peak Pne0
- Qualifier
- at Amaxe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The subsequent decline reduced Pn to less than one-third of peak Pn at Amax.”
t0“Tobacco Plant”
Claim · model-written summary
After 37% final area, tobacco leaf nitrogen content followed a common developmental pattern.
- Taxon
- Tobacco PlantNicotiana tabacumt0
- Outcome
- nitrogen content (w/w)e0
- Qualifier
- after 37% Amaxe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Data for the nitrogen content (w/w) of the leaves after 37% Amax could be combined in a manner similar to that described for Pn.”
t0“Tobacco Plant”
Claim · model-written summary
Tobacco leaf photosynthesis, nitrogen content and ontogeny were directly related after peak photosynthesis.
- Taxon
- Tobacco PlantNicotiana tabacumt0
- Organ / stage
- leaf ontogenye0
- Outcome
- Pn, nitrogen content and leaf ontogenye0
- Qualifier
- after peak Pne0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Pn, nitrogen content and leaf ontogeny were therefore directly related after peak Pn had been attained.”
t0“Tobacco Plant”