Abstract
ABSTRACT Tomato plants were exposed to four concentrations of CO 2 (350, 700, 1050 or 1400 μmol CO 2 mol −1 ) for 31 d. The light‐saturated rate of photosynthesis (A) of the unshaded fifth leaf was measured at either an ambient CO 2 concentration of 350 μmol CO 2 mol −1 [ A (350)] or at the level of CO 2 at which the plants were grown. The chloroplast protein composition and the level of transcripts of nuclear or plastid photosynthesis‐associated genes (PAGs), as well as the main carbohydrate content of the fifth leaf maintained horizontal and unshaded, were also measured during leaf development. At 60 and 95% leaf expansion, the A of high‐CO 2 ‐grown plants measured at growth CO 2 was higher than the A (350) of the plants grown at ambient CO 2 . However, in the fully mature leaves, A (growth CO 2 ) declined linearly as growth CO 2 concentration increased. The A (350) of plants exposed to elevated CO 2 up to 60% leaf expanion had not acclimated to high CO 2 . At 95% leaf expansion, A (350) was lower in plants grown at high CO 2 . A versus CO 2 ( C i ) for mature leaves showed that A of the plants grown at high CO 2 was lower over the entire range than that for plants grown at present ambient CO 2 concentration. Lines fitted to the linear part of the A / C i curves were concurrent at a C i of 49μmol CO 2 mol −1 and A =−1.21μmol CO 2 m −2 s −1 . This C t value is close to Λ * (46 μmol CO 2 mol −1 ), the compensation point at 27°C calculated from the equation described in Brooks & Farquhar (1985, Planta 165, 397–406). This A is an estimate of respiration in the light ( R 1 ) and was not affected by acclimation to elevated CO 2 . Thylakoid proteins (photo‐system I core protein, D 1 and D 2 of the photosystem II core complex, cytochrome f ) were all reduced by elevated CO 2 only in the fully mature leaves (31d exposure), whereas the large and small subunits of Rubisco and Rubisco activase proteins had already declined after 22 d exposure. Transcript levels of the plastid‐encoded PAG ( rbcL, psbA, psaA‐B ) were reduced in the mature leaves by elevated CO 2 when expressed on a total RNA basis, but they were not sensitive to elevated CO 2 when expressed on a chloroplast 16S rRNA basis. However, rbcS, rca and cab mRNA transcripts were lower in the plants grown at high CO 2 than in control plants after 22 d exposure when expressed on a nuclear rRNA basis. The loss of these nuclear PAGs was correlated with an accumulation of soluble sugars and starch.
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Claims 12
Claim · model-written summary
At 60 and 95% expansion, photosynthesis at growth CO2 exceeded ambient-grown photosynthesis at ambient CO2.
- Taxon
- tomato plants
Solanum lycopersicumt0 - Organ / stage
- 60 and 95% leaf expansione0
- Treatment
- high‐CO 2e0
- Outcome
- Ae0
- Direction
- highere0
- Comparator
- plants grown at ambient CO 2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At 60 and 95% leaf expansion, the A of high‐CO 2 ‐grown plants measured at growth CO 2 was higher than the A (350) of the plants grown at ambient CO 2”
t0“tomato plants”
Claim · model-written summary
In mature leaves, photosynthesis at growth CO2 declined linearly with increasing growth CO2.
- Taxon
- tomato plantsSolanum lycopersicumt0
- Organ / stage
- fully mature leavese0
- Treatment
- growth CO 2 concentratione0
- Outcome
- A (growth CO 2 )e0
- Direction
- declinede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in the fully mature leaves, A (growth CO 2 ) declined linearly as growth CO 2 concentration increased”
t0“tomato plants”
Claim · model-written summary
Photosynthesis at ambient CO2 had not acclimated by 60% leaf expansion.
- Taxon
- tomato plantsSolanum lycopersicumt0
- Organ / stage
- 60% leaf expanione0
- Outcome
- had not acclimated to high CO 2e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The A (350) of plants exposed to elevated CO 2 up to 60% leaf expanion had not acclimated to high CO 2”
t0“tomato plants”
Claim · model-written summary
At 95% expansion, ambient-measured photosynthesis was lower after high CO2 growth.
- Taxon
- tomato plantsSolanum lycopersicumt0
- Organ / stage
- 95% leaf expansione0
- Treatment
- high CO 2e0
- Outcome
- A (350)e0
- Direction
- lowere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At 95% leaf expansion, A (350) was lower in plants grown at high CO 2”
t0“tomato plants”
Claim · model-written summary
Mature high-CO2 plants had lower photosynthesis across the full CO2 response range.
- Taxon
- tomato plantsSolanum lycopersicumt0
- Treatment
- high CO 2e0
- Outcome
- Ae0
- Direction
- lowere0
- Comparator
- present ambient CO 2 concentratione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A of the plants grown at high CO 2 was lower over the entire range than that for plants grown at present ambient CO 2 concentration”
t0“tomato plants”
Claim · model-written summary
Respiration in light was unaffected by acclimation to elevated CO2.
- Taxon
- tomato plantsSolanum lycopersicumt0
- Treatment
- acclimation to elevated CO 2e0
- Outcome
- respiration in the lighte0
- Direction
- not affectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This A is an estimate of respiration in the light ( R 1 ) and was not affected by acclimation to elevated CO 2”
t0“tomato plants”
Claim · model-written summary
Elevated CO2 reduced mature-leaf thylakoid proteins.
- Taxon
- tomato plantsSolanum lycopersicumt0
- Organ / stage
- fully mature leavese0
- Treatment
- elevated CO 2e0
- Outcome
- Thylakoid proteinse0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Thylakoid proteins (photo‐system I core protein, D 1 and D 2 of the photosystem II core complex, cytochrome f ) were all reduced by elevated CO 2 only in the fully mature leaves (31d exposure)”
t0“tomato plants”
Claim · model-written summary
Rubisco subunits and activase declined after 22 days of elevated CO2.
- Taxon
- tomato plantsSolanum lycopersicumt0
- Treatment
- 22 d exposuree0
- Outcome
- large and small subunits of Rubisco and Rubisco activase proteinse0
- Direction
- declinede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the large and small subunits of Rubisco and Rubisco activase proteins had already declined after 22 d exposure”
t0“tomato plants”
Claim · model-written summary
Elevated CO2 reduced plastid gene transcripts on a total-RNA basis.
- Taxon
- tomato plantsSolanum lycopersicumt0
- Treatment
- elevated CO 2e0
- Gene
- rbcL, psbA, psaA‐Be0
- Outcome
- Transcript levels of the plastid‐encoded PAGe0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Transcript levels of the plastid‐encoded PAG ( rbcL, psbA, psaA‐B ) were reduced in the mature leaves by elevated CO 2 when expressed on a total RNA basis”
t0“tomato plants”
Claim · model-written summary
Elevated CO2 did not alter plastid transcripts on a chloroplast 16S rRNA basis.
- Taxon
- tomato plantsSolanum lycopersicumt0
- Treatment
- elevated CO 2e0
- Outcome
- chloroplast 16S rRNA basise0
- Direction
- not sensitivee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“they were not sensitive to elevated CO 2 when expressed on a chloroplast 16S rRNA basis”
t0“tomato plants”
Claim · model-written summary
High CO2 reduced nuclear photosynthesis-associated transcripts after 22 days.
- Taxon
- tomato plantsSolanum lycopersicumt0
- Treatment
- high CO 2e0
- Gene
- rbcS, rca and cabe0
- Outcome
- mRNA transcriptse0
- Direction
- lowere0
- Comparator
- control plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“rbcS, rca and cab mRNA transcripts were lower in the plants grown at high CO 2 than in control plants after 22 d exposure”
t0“tomato plants”
Claim · model-written summary
Loss of nuclear photosynthesis-associated transcripts correlated with soluble sugar and starch accumulation.
- Taxon
- tomato plantsSolanum lycopersicumt0
- Compound
- soluble sugars and starche0
- Outcome
- loss of these nuclear PAGse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The loss of these nuclear PAGs was correlated with an accumulation of soluble sugars and starch”
t0“tomato plants”
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